JP4349296B2 - Loudspeaker - Google Patents

Description

  The present invention relates to a loudspeaker used in homes, buildings, factories, and the like.

  Conventionally, in a loudspeaker such as an interphone, a telephone, or a PHS, a closed loop is formed by acoustic feedback from a speaker to a microphone and impedance mismatch in a hybrid circuit (2-4 wire conversion circuit), and the gain of the amplifier is large. Since howling occurs when the closed-loop gain becomes 1 or more for reasons such as too much, suppression of howling has become an indispensable issue in securing call quality.

  Therefore, conventionally, a howling suppression method has been used in which a closed loop gain is suppressed by inserting a predetermined amount of loss into a received signal or a transmitted signal in accordance with the level of the transmitted / received signal. In addition, there is another method that uses an echo canceller, but it tends to be unstable when the echo path changes suddenly due to a transient state where the coefficient of the adaptive filter in the echo canceller has not converged or system fluctuations. Often used in conjunction with insertion loss.

  In any of the above cases, if the amount of insertion loss is increased too much, the quality of the call will be degraded during a call (sound will be interrupted). Is desirable.

  In response to such problems, the present inventors have already monitored the gain margin of the closed loop formed in the voice communication system as needed, and adaptively adjust the insertion loss amount based on the estimated gain margin value. A loudspeaker has been proposed (see Patent Document 1).

FIG. 18A is a block diagram showing a loudspeaker according to the above-mentioned application. From the microphone 1 that outputs the collected sound as a voice signal on the transmission side (hereinafter referred to as a transmission signal), A first amplifier 2 that amplifies the transmitted signal, a speaker 3 that rings in response to a voice signal on the receiving side (hereinafter referred to as a received signal), and a second that amplifies the received signal output to the speaker 3. A predetermined amount in the amplifier 4, the hybrid circuit 5 as 2-4 line conversion means for performing 2-4 line conversion between the transmission side and reception side and the external communication line, and the signal path on the transmission side and reception side Attenuators (attenuators) 6 ₁ , 6 ₂ , a controller 7 for variably controlling the loss amounts of the attenuators 6 ₁ , 6 ₂ , and a response to the sample signal sent to the signal path Depending on the signal, microphone 1 to speaker 3 Insertion loss amount adjusting means 8 is provided for estimating a gain margin in a closed loop formed by acoustic coupling to and reflection in the hybrid circuit 5 and adjusting a loss amount based on an estimation result via a controller 7. The insertion loss amount adjusting means 8 can be provided on the signal path on the transmission side.

On the other hand, FIG. 4B is a block diagram showing a specific configuration of the insertion loss amount adjusting means 8, and an impulse signal generator 9 for sending an impulse signal as a sample signal to the signal path on the reception side, and the reception signal An adder 10 for adding the impulse signal to the envelope, an envelope detector 11 for detecting the envelope of the response signal to the impulse signal, and a closed loop gain for estimating the gain margin in the closed loop system based on the output signal of the envelope detector 11 And a margin estimation unit 12. Here, the closed loop gain margin estimation unit 12 compares the output signal level of the envelope detector 11 with a predetermined threshold level, and a determination unit that estimates the gain margin value of the closed loop system based on the comparison result. 14. The sample signal may be a single pulse signal with a sufficiently short pulse width or a burst signal (burst noise). Then, as shown in FIG. 19, second amplifier 4 → speaker 3 → microphone 1 → first amplifier 2 → attenuator 6 ₁ → hybrid circuit 5 → attenuator 6 ₂ → insertion loss amount adjusting means 8 → second A closed loop is formed by the amplifier 4.

Thus, the output signal of the adder 10 is a response signal when a sample signal is input to the closed loop system, and the impulse response of the closed loop system can be estimated by observing the output signal of the adder 10. . The extracted envelope component is closely related to the real part of the dominant pole (the pole closest to the imaginary axis on the complex plane) in the transfer function of the closed-loop system. Stability, that is, gain margin can be estimated. However, in the output signal of the adder 10 in FIG. 18A, the transmission / reception voice signal and the ambient noise are superimposed in addition to the response component for the sample signal, and the insertion loss amount adjusting means 8 has a response to the sample signal. Since there is no means for extracting only the components, there is a problem that the estimation accuracy of the gain margin value deteriorates when the level of the voiced section and the ambient noise signal is large. Among these, for the deterioration of the estimation accuracy due to the transmitted / received speech, a silence detector for detecting a silent section during a call is provided from the level of the received signal (or may be the level of the transmitted signal). Only when a silent section is detected by the detector, a sample signal (impulse signal or burst noise) is input to the closed-loop system, and the closed-loop gain margin estimation unit 12 performs an estimation process of the gain margin value to increase the estimation accuracy. Can be improved.
Japanese Patent Laid-Open No. 10-257159

  However, when a steady ambient noise signal exists in the closed loop of the above-mentioned loudspeaker communication system and its level is large, the loudspeaker according to the above application cannot accurately estimate the gain margin value. . In addition, in the above method, since it is necessary to stop the gain margin value estimation process when a voice signal is present in the closed loop, this is handled when the gain margin value of the system fluctuates during a call. It may not be possible and the system may become unstable.

  The present invention has been made in view of the above problems, and its object is to obtain a gain with sufficient accuracy even when ambient noise and audio signals are present in a closed loop and the levels of those signals are large. An object of the present invention is to provide a loudspeaker capable of estimating a margin value and always realizing a stable call.

In order to achieve the above object, the first aspect of the present invention provides a microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And a control means for variably controlling the amount of loss inserted from the loss insertion means, and a control means for estimating a gain margin in a closed loop formed through a microphone and a speaker according to a response signal to the sample signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the insertion loss, and the insertion loss amount adjusting means sends a sample signal to the signal path. A sample signal generator, an adder for adding the sample signal to the audio signal, an envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path, and an envelope A closed loop gain margin estimation unit that estimates a gain margin in the closed loop based on the output signal of the line detector, and a timing control for sending the sample signal multiple times from the sample signal generator to the signal path at predetermined time intervals A synchronization control unit, a synchronization addition averaging unit that is provided in a preceding stage of the envelope detector and that receives timing information from the synchronization control unit and performs a synchronous addition averaging process on the response signal with respect to the sample signal; and a self-of-signal that exists in the closed loop ; and a self-correlation function calculation section for calculating a correlation function, the synchronization control unit comprises a time shift amount is a variable of the autocorrelation function, a predetermined value In order to minimize the time required for the synchronous addition process by collating the relationship with the number of times of synchronous addition necessary to obtain the suppression amount of the above noise component with the autocorrelation function calculated by the autocorrelation function calculation unit The transmission interval and the number of synchronous additions necessary for the sample signal are obtained, and the transmission interval and the number of synchronous additions are adjusted .

In order to achieve the above object, the invention according to claim 2 is a microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And a control means for variably controlling the amount of loss inserted from the loss insertion means, and a control means for estimating a gain margin in a closed loop formed through a microphone and a speaker according to a response signal to the sample signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the insertion loss, and the insertion loss amount adjusting means sends a sample signal to the signal path. A sample signal generator, an adder for adding the sample signal to the audio signal, an envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path, and an envelope A closed loop gain margin estimation unit that estimates a gain margin in the closed loop based on the output signal of the line detector, and a timing control for sending the sample signal multiple times from the sample signal generator to the signal path at predetermined time intervals A synchronization control unit, a synchronization addition averaging unit that is provided in a preceding stage of the envelope detector and receives the timing information from the synchronization control unit and performs a synchronous addition averaging process on the response signal with respect to the sample signal; and an ambient noise existing in the closed loop The noise level estimation unit for estimating the level and the synchronous addition operation in the synchronous addition averaging unit based on the estimation result by the noise level estimation unit A synchronization addition number adjustment unit that adjusts the noise level, and the synchronization addition number adjustment unit is estimated by the noise level estimation unit based on the statistical properties of the ambient noise level and the number of synchronization additions that have been quantitatively examined in advance. It is characterized in that the minimum number of synchronous additions necessary for minimizing the delay time associated with the synchronous addition average is set for the ambient noise level to be generated .

According to a third aspect of the present invention, in the second aspect of the present invention, the insertion loss amount adjusting means includes an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and the noise is extracted from the extracted ambient noise signal. The level estimation unit estimates the level of ambient noise existing in the closed loop.

In order to achieve the above object, a fourth aspect of the present invention provides a microphone that outputs the collected sound as a voice signal on the transmission side, a first amplification unit that amplifies the voice signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And a control means for variably controlling the amount of loss inserted from the loss insertion means, and a control means for estimating a gain margin in a closed loop formed through a microphone and a speaker according to a response signal to the sample signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the insertion loss, and the insertion loss amount adjusting means sends a sample signal to the signal path. A sample signal generator, an adder for adding the sample signal to the audio signal, an envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path, and an envelope A closed loop gain margin estimation unit that estimates a gain margin in the closed loop based on the output signal of the line detector, and a timing control for sending the sample signal multiple times from the sample signal generator to the signal path at predetermined time intervals A synchronization control unit, a synchronization addition averaging unit that is provided in a preceding stage of the envelope detector and receives the timing information from the synchronization control unit and performs a synchronous addition averaging process on the response signal with respect to the sample signal; and an ambient noise existing in the closed loop The noise level estimation unit that estimates the level and the sample signal transmission level is adjusted based on the estimation results from the noise level estimation unit A transmission level adjustment unit, and an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and the noise level estimation unit is configured to perform a closed loop from the ambient noise signal extracted by the ambient noise extraction unit. The transmission level adjustment unit is configured by estimating the level of ambient noise existing, and the ratio of the sample signal transmission level to the ambient noise level in the closed loop is set so that the sample signal transmission with respect to the ambient noise level before the sample signal is transmitted to the closed loop. The transmission level of the sample signal is adjusted so as to be a predetermined value or more with respect to the ratio of the levels .

In order to achieve the above object, a fifth aspect of the present invention provides a microphone that outputs a collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And a control means for variably controlling the amount of loss inserted from the loss insertion means, and a control means for estimating a gain margin in a closed loop formed through a microphone and a speaker according to a response signal to the sample signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the insertion loss, and the insertion loss amount adjusting means sends a sample signal to the signal path. A sample signal generator, an adder for adding the sample signal to the audio signal, an envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path, and an envelope A closed loop gain margin estimation unit that estimates a gain margin in the closed loop based on the output signal of the line detector, and a timing control for sending the sample signal multiple times from the sample signal generator to the signal path at predetermined time intervals A synchronization control unit, a synchronization addition averaging unit that is provided in a preceding stage of the envelope detector and receives timing information from the synchronization control unit and performs a synchronous addition averaging process on the response signal with respect to the sample signal, and a signal transmitted during the closed loop Ambient noise extraction unit that extracts ambient noise signals, and estimates the level of ambient noise that exists in the closed loop from the extracted ambient noise signals A noise level estimation unit, a transmission level adjustment unit that adjusts the transmission level of the sample signal based on the estimation result by the noise level estimation unit, and the number of synchronization additions in the synchronization addition averaging unit based on the estimation result by the noise level estimation unit And a sending level adjusting unit that sends the sample signal to the ambient noise level before the sample signal is sent to the closed loop, with the ratio of the sample signal sending level to the ambient noise level in the closed loop being adjusted. The level of the sample signal is adjusted so that the level ratio is equal to or greater than a predetermined value. The synchronization addition number adjustment unit is a statistical property of the ambient noise level and the number of synchronization additions that are quantitatively examined in advance. In order to minimize the delay time associated with the synchronous averaging with respect to the ambient noise level estimated by the noise level estimation unit It is characterized in that the minimum number of synchronous additions required is set .

In order to achieve the above object, the invention according to claim 6 is a microphone that outputs the collected sound as an audio signal on the transmission side, a first amplification means that amplifies the audio signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And control means for variably controlling the amount of loss inserted from the loss insertion means, and estimating and controlling the gain margin in the closed loop formed through the microphone and the speaker according to the response signal to the pseudo white signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the means, the insertion loss amount adjusting means is a pseudo white with a finite period in the signal path A pseudo white signal generator for inserting a signal, an adder for adding the pseudo white signal to the audio signal, and the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path. A cross-correlation calculation unit that obtains a cross-correlation value and estimates a closed-loop impulse response based on the obtained cross-correlation value, and an envelope detector that detects an envelope of the closed-loop impulse response signal estimated by the cross-correlation calculation unit A closed-loop gain margin estimation unit that estimates a gain margin in the closed-loop based on an output signal of the envelope detector, and a pseudo-white signal is transmitted from the pseudo-white signal generator to the signal path a plurality of times at predetermined time intervals. A synchronization control unit that controls the timing of the signal and a cross-correlation calculation unit that receives timing information from the synchronization control unit that is provided in the front stage of the envelope detector. A synchronous addition averaging unit that performs synchronous addition averaging processing on the estimated closed-loop impulse response signal, and an autocorrelation function calculation unit that calculates an autocorrelation function of a signal existing in the closed loop. The correlation between the time shift amount, which is a variable of the correlation function, and the number of synchronous additions necessary to obtain a noise component suppression amount greater than or equal to a predetermined value is checked against the autocorrelation function calculated by the autocorrelation function calculation unit. To obtain the transmission interval and the number of synchronous additions of the pseudo white signal from the pseudo white signal generator necessary for minimizing the time required for the synchronous addition processing, and adjust the transmission interval and the number of synchronous additions. To do.

In order to achieve the above object, a seventh aspect of the present invention provides a microphone that outputs the collected sound as a voice signal on the transmission side, a first amplification means that amplifies the voice signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And control means for variably controlling the amount of loss inserted from the loss insertion means, and estimating and controlling the gain margin in the closed loop formed through the microphone and the speaker according to the response signal to the pseudo white signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the means, the insertion loss amount adjusting means is a pseudo white with a finite period in the signal path A pseudo white signal generator for inserting a signal, an adder for adding the pseudo white signal to the audio signal, and the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path. A cross-correlation calculation unit that obtains a cross-correlation value and estimates a closed-loop impulse response based on the obtained cross-correlation value, and an envelope detector that detects an envelope of the closed-loop impulse response signal estimated by the cross-correlation calculation unit A closed-loop gain margin estimation unit that estimates a gain margin in the closed-loop based on an output signal of the envelope detector, and a pseudo-white signal is transmitted from the pseudo-white signal generator to the signal path a plurality of times at predetermined time intervals. A synchronization control unit that controls the timing of the signal and a cross-correlation calculation unit that receives timing information from the synchronization control unit that is provided in the front stage of the envelope detector. Based on the estimation results from the noise level estimation unit, the synchronous addition averaging unit that performs synchronous addition averaging processing on the estimated closed loop impulse response signal, the noise level estimation unit that estimates the level of ambient noise existing in the closed loop A synchronization addition number adjustment unit that adjusts the number of synchronization additions in the addition averaging unit, and the synchronization addition number adjustment unit is based on the statistical properties of the ambient noise level and the number of synchronization additions that have been quantitatively examined in advance. The minimum number of synchronous additions necessary for minimizing the delay time associated with the synchronous addition average is set for the ambient noise level estimated by the noise level estimation unit .

The invention according to claim 8 is the invention according to claim 7 , wherein the insertion loss amount adjusting means includes an ambient noise extraction unit for extracting an ambient noise signal from the signal transmitted during the closed loop, and noise is extracted from the extracted ambient noise signal. The level estimation unit estimates the level of ambient noise existing in the closed loop .

In order to achieve the above object, a ninth aspect of the present invention provides a microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And control means for variably controlling the amount of loss inserted from the loss insertion means, and estimating and controlling the gain margin in the closed loop formed through the microphone and the speaker according to the response signal to the pseudo white signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the means, the insertion loss amount adjusting means is a pseudo white with a finite period in the signal path A pseudo white signal generator for inserting a signal, an adder for adding the pseudo white signal to the audio signal, and the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path. A cross-correlation calculation unit that obtains a cross-correlation value and estimates a closed-loop impulse response based on the obtained cross-correlation value, and an envelope detector that detects an envelope of the closed-loop impulse response signal estimated by the cross-correlation calculation unit A closed-loop gain margin estimation unit that estimates a gain margin in the closed-loop based on an output signal of the envelope detector, and a pseudo-white signal is transmitted from the pseudo-white signal generator to the signal path a plurality of times at predetermined time intervals. A synchronization control unit that controls the timing of the signal and a cross-correlation calculation unit that receives timing information from the synchronization control unit that is provided in the front stage of the envelope detector. Based on the estimation result by the noise level estimation unit, the noise level estimation unit for estimating the level of ambient noise existing in the closed loop, A white level signal transmission level adjustment unit, and a surrounding noise extraction unit for extracting an ambient noise signal from a signal transmitted during a closed loop. The noise level estimation unit is extracted by the ambient noise extraction unit. The level of ambient noise existing in the closed loop is estimated from the ambient noise signal, and the transmission level adjustment unit sends the ratio of the pseudo white signal transmission level to the ambient noise level in the closed loop, and the pseudo white signal is transmitted to the closed loop. The pseudo white signal transmission level is adjusted to be equal to or greater than a predetermined value with respect to the ratio of the pseudo white signal transmission level to the previous ambient noise level. It is characterized by adjusting .

In order to achieve the above object, a tenth aspect of the present invention provides a microphone that outputs the collected sound as a voice signal on the transmission side, a first amplification means that amplifies the voice signal from the microphone, A speaker that rings in response to an audio signal, a second amplifying unit that amplifies the audio signal output to the speaker, and a loss insertion unit that inserts a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side And control means for variably controlling the amount of loss inserted from the loss insertion means, and estimating and controlling the gain margin in the closed loop formed through the microphone and the speaker according to the response signal to the pseudo white signal sent to the signal path Insertion loss amount adjusting means for adjusting the loss amount based on the estimation result via the means, and the insertion loss amount adjusting means is a pseudo white having a finite period in the signal path. A pseudo white signal generator for inserting a signal, an adder for adding the pseudo white signal to the audio signal, and the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path. A cross-correlation calculation unit that obtains a cross-correlation value and estimates a closed-loop impulse response based on the obtained cross-correlation value, and an envelope detector that detects an envelope of the closed-loop impulse response signal estimated by the cross-correlation calculation unit A closed-loop gain margin estimation unit that estimates a gain margin in the closed-loop based on an output signal of the envelope detector, and a pseudo-white signal is transmitted from the pseudo-white signal generator to the signal path a plurality of times at predetermined time intervals. And a cross-correlation calculation unit that receives timing information from the synchronization control unit provided in the previous stage of the envelope detector. A synchronous addition averaging unit that performs synchronous addition averaging processing of the estimated closed-loop impulse response signal, an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and a closed loop from the extracted ambient noise signal A noise level estimator that estimates the level of ambient noise existing in the sound source, a transmission level adjuster that adjusts the transmission level of the pseudo white signal based on an estimation result by the noise level estimator, and an estimation result by the noise level estimator A synchronous addition number adjusting unit that adjusts the number of synchronous additions in the synchronous addition averaging unit, and the transmission level adjustment unit sends the sample signal to the closed loop with the ratio of the sample signal transmission level to the ambient noise level in the closed loop. So that the ratio of the sample signal transmission level to the previous ambient noise level is equal to or greater than a predetermined value. The synchronization addition frequency adjustment unit is configured by adjusting the transmission level, and the ambient noise level estimated by the noise level estimation unit based on the statistical characteristics of the ambient noise level and the synchronization addition frequency that have been quantitatively examined in advance. The minimum number of synchronous additions necessary for minimizing the delay time associated with the synchronous addition average is set .

According to the first aspect of the present invention, the acoustic coupling from the speaker to the microphone or the 2-4 line conversion used when the 2-4 line conversion needs to be performed between the transmission side and the reception side and the external communication line. For the closed loop system formed due to reflection due to impedance mismatch in the means, the gain margin value is estimated by the attenuation characteristic of the envelope component of the response signal observed when the sample signal is input, and the desired gain Since the amount of insertion loss is adjusted by calculating the excess and deficiency relative to the margin value, the gain margin of the closed loop system until howling occurs can be maintained at a desired value, and stable call quality without causing howling Can be maintained, and the amount of insertion loss is not increased more than necessary, thereby increasing the possibility of realizing two-way simultaneous call performance. Moreover, the synchronization control unit controls the transmission timing of the sample signal, the synchronous addition averaging unit performs the moving average process synchronized with the sample signal, and the envelope detector detects the envelope component from the output signal of the synchronous addition average unit. Because it is extracted, even when the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced, the gain margin value is estimated with sufficient accuracy, and the insertion loss amount can be set to an appropriate value As a result, a stable call can be realized at all times, and the sample signal is transmitted so as to minimize the time required for the synchronous addition process from the autocorrelation function of the signal existing in the closed loop calculated in advance. The gain margin value estimation process can be speeded up by adjusting the interval and the number of synchronous additions.

According to the second aspect of the present invention, acoustic coupling from the speaker to the microphone, or 2-4 line conversion used when 2-4 line conversion needs to be performed between the transmission side and the reception side and the external communication line. For the closed loop system formed due to reflection due to impedance mismatch in the means, the gain margin value is estimated by the attenuation characteristic of the envelope component of the response signal observed when the sample signal is input, and the desired gain Since the amount of insertion loss is adjusted by calculating the excess and deficiency relative to the margin value, the gain margin of the closed loop system until howling occurs can be maintained at a desired value, and stable call quality without causing howling Can be maintained, and the amount of insertion loss is not increased more than necessary, thereby increasing the possibility of realizing two-way simultaneous call performance. Moreover, the synchronization control unit controls the transmission timing of the sample signal, the synchronous addition averaging unit performs the moving average process synchronized with the sample signal, and the envelope detector detects the envelope component from the output signal of the synchronous addition average unit. Because it is extracted, even when the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced, the gain margin value is estimated with sufficient accuracy, and the insertion loss amount can be set to an appropriate value Therefore, it is possible to always realize a stable call, and furthermore, since the number of synchronous additions can be set to the minimum necessary according to the level of ambient noise existing in the closed loop system, the calculation required for the synchronous addition processing Time can be minimized, and the sample signal can be received by minimizing the number of times the sample signal is sent to estimate the gain margin once. Hearing on the discomfort caused by sounds superimposed on the issue, it is possible to reduce the discomfort.

According to the invention of claim 3 , in addition to the effect of the invention of claim 2 , even when the ambient noise level in the closed loop changes during the process of estimating the gain margin value, the sample signal is adapted to this. Therefore, even when the ambient noise level fluctuates, the gain margin value can be accurately estimated following this.

According to the fourth aspect of the present invention, the acoustic coupling from the speaker to the microphone, or the 2-4 line conversion used when the 2-4 line conversion needs to be performed between the transmission side and the reception side and the external communication line. For the closed loop system formed due to reflection due to impedance mismatch in the means, the gain margin value is estimated by the attenuation characteristic of the envelope component of the response signal observed when the sample signal is input, and the desired gain Since the amount of insertion loss is adjusted by calculating the excess and deficiency relative to the margin value, the gain margin of the closed loop system until howling occurs can be maintained at a desired value, and stable call quality without causing howling Can be maintained, and the amount of insertion loss is not increased more than necessary, thereby increasing the possibility of realizing two-way simultaneous call performance. Moreover, the synchronization control unit controls the transmission timing of the sample signal, the synchronous addition averaging unit performs the moving average process synchronized with the sample signal, and the envelope detector detects the envelope component from the output signal of the synchronous addition average unit. Because it is extracted, even when the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced, the gain margin value is estimated with sufficient accuracy, and the insertion loss amount can be set to an appropriate value Thus, a stable call can be realized at all times. Further, by setting the level of the sample signal sent to the closed loop system to be sufficiently large with respect to the ambient noise level, a high S / N at the observation point. The response signal to the sample signal can be obtained with the ratio, and the accuracy of the gain margin value estimation can be improved. Even when the ambient noise level changes, the sample signal transmission level or the number of synchronous additions is adjusted to adjust to this, so even if the ambient noise level fluctuates, it will follow this. Thus, the gain margin value can be estimated with high accuracy.

According to the invention of claim 5 , acoustic coupling from the speaker to the microphone, or 2-4 line conversion used when 2-4 line conversion is required between the transmitting side and the receiving side and an external telephone line. For the closed loop system formed due to reflection due to impedance mismatch in the means, the gain margin value is estimated by the attenuation characteristic of the envelope component of the response signal observed when the sample signal is input, and the desired gain Since the amount of insertion loss is adjusted by calculating the excess and deficiency relative to the margin value, the gain margin of the closed loop system until howling occurs can be maintained at a desired value, and stable call quality without causing howling Can be maintained, and the amount of insertion loss is not increased more than necessary, thereby increasing the possibility of realizing two-way simultaneous call performance. Moreover, the synchronization control unit controls the transmission timing of the sample signal, the synchronous addition averaging unit performs the moving average process synchronized with the sample signal, and the envelope detector detects the envelope component from the output signal of the synchronous addition average unit. Because it is extracted, even when the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced, the gain margin value is estimated with sufficient accuracy, and the insertion loss amount can be set to an appropriate value Therefore, even when the ambient noise level in the closed loop changes during the process of estimating the gain margin value, the sample signal transmission level is adapted to this. Since the number of synchronous additions is adjusted, even when the ambient noise level fluctuates, the gain margin value can be accurately estimated following this.

According to the sixth aspect of the present invention, the acoustic coupling from the speaker to the microphone, or the 2-4 line conversion used when the 2-4 line conversion needs to be performed between the transmission side and the reception side and the external communication line. The cross-correlation value between the response signal observed when a pseudo white signal with a finite period is input and the pseudo white signal is obtained for a closed loop system formed due to reflection due to impedance mismatch in the means. The gain margin value is estimated based on the attenuation characteristic of the envelope component of the impulse response signal of the closed loop system estimated from the obtained cross-correlation value, and the amount of insertion loss is adjusted by calculating the excess or deficiency relative to the desired gain margin value. Therefore, the gain margin of the closed loop system until howling can be maintained at a desired value, and stable call quality can be maintained without generating howling. In addition, since the amount of insertion loss is not increased more than necessary, the possibility of two-way simultaneous call performance is increased, and the pseudo white signal is used to estimate the gain margin, so that the user feels uncomfortable. In addition, the synchronous control unit controls the transmission timing of the pseudo white signal, the synchronous addition averaging unit performs the moving average process synchronized with the pseudo white signal, and the output of the synchronous addition average unit Envelope components are extracted from the signal by the envelope detector, so even if the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced and the gain margin value is estimated with sufficient accuracy Therefore, the amount of insertion loss can be set to an appropriate value, so that a stable call can always be realized, and the autocorrelation of the signal existing in the closed loop calculated in advance is possible. More, it is possible to speed up the process of estimating the gain margin value by adjusting the transmission interval and the synchronization addition number of the pseudo white signal to minimize the time required for the synchronous addition processing.

According to the invention of claim 7 , acoustic coupling from a speaker to a microphone, or 2-4 line conversion used when 2-4 line conversion needs to be performed between the transmitting side and the receiving side and an external telephone line. The cross-correlation value between the response signal observed when a pseudo white signal with a finite period is input and the pseudo white signal is obtained for a closed loop system formed due to reflection due to impedance mismatch in the means. The gain margin value is estimated based on the attenuation characteristic of the envelope component of the impulse response signal of the closed loop system estimated from the obtained cross-correlation value, and the amount of insertion loss is adjusted by calculating the excess or deficiency relative to the desired gain margin value. Therefore, the gain margin of the closed loop system until howling can be maintained at a desired value, and stable call quality can be maintained without generating howling. In addition, since the amount of insertion loss is not increased more than necessary, the possibility of two-way simultaneous call performance is increased, and the pseudo white signal is used to estimate the gain margin, so that the user feels uncomfortable. In addition, the synchronous control unit controls the transmission timing of the pseudo white signal, the synchronous addition averaging unit performs the moving average process synchronized with the pseudo white signal, and the output of the synchronous addition average unit Envelope components are extracted from the signal by the envelope detector, so even if the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced and the gain margin value is estimated with sufficient accuracy Therefore, the amount of insertion loss can be set to an appropriate value, so that stable calls can be realized at all times, and synchronous addition is performed according to the level of ambient noise existing in the closed loop system. Since the number can be set to the minimum necessary, the calculation time required for the synchronous addition process can be minimized, and the number of pseudo white signal transmissions required for one gain margin value estimation process can be minimized. By doing so, it is possible to reduce auditory discomfort and discomfort due to the fact that the pseudo white signal is superimposed on the received signal.

According to the eighth aspect of the invention, in addition to the effect of the seventh aspect of the invention, even when the ambient noise level in the closed loop changes during the process of estimating the gain margin value, the pseudo white color is adapted to this. Since the signal transmission level or the number of synchronous additions is adjusted, even when the ambient noise level fluctuates, the gain margin value can be accurately estimated following this.

According to the ninth aspect of the present invention, the acoustic coupling from the speaker to the microphone, or the 2-4 line conversion used when the 2-4 line conversion needs to be performed between the transmission side and the reception side and the external communication line. The cross-correlation value between the response signal observed when a pseudo white signal with a finite period is input and the pseudo white signal is obtained for a closed loop system formed due to reflection due to impedance mismatch in the means. The gain margin value is estimated based on the attenuation characteristic of the envelope component of the impulse response signal of the closed loop system estimated from the obtained cross-correlation value, and the amount of insertion loss is adjusted by calculating the excess or deficiency relative to the desired gain margin value. Therefore, the gain margin of the closed loop system until howling can be maintained at a desired value, and stable call quality can be maintained without generating howling. In addition, since the amount of insertion loss is not increased more than necessary, the possibility of two-way simultaneous call performance is increased, and the pseudo white signal is used to estimate the gain margin, so that the user feels uncomfortable. In addition, the synchronous control unit controls the transmission timing of the pseudo white signal, the synchronous addition averaging unit performs the moving average process synchronized with the pseudo white signal, and the output of the synchronous addition average unit Envelope components are extracted from the signal by the envelope detector, so even if the level of stationary ambient noise that exists in the closed loop is large, the effect of ambient noise is reduced and the gain margin value is estimated with sufficient accuracy Therefore, the amount of insertion loss can be set to an appropriate value, so that stable conversation can be realized at all times, and the level of the pseudo white signal sent to the closed loop system can be set to the ambient noise level. By setting a sufficient size for the signal, it is possible to obtain a response signal for the pseudo white signal with a high S / N ratio at the observation point, improve the estimation accuracy of the gain margin value, Even when the ambient noise level in the closed loop changes during the gain margin estimation process, the level of ambient noise fluctuates in order to adjust the sending level of the pseudo white signal or the number of synchronous additions in response to this. Even in such a case, the gain margin value can be accurately estimated following this.

According to the invention of claim 10 , acoustic coupling from a speaker to a microphone, or 2-4 line conversion used when 2-4 line conversion needs to be performed between a transmitting side and a receiving side and an external communication line. The cross-correlation value between the response signal observed when a pseudo white signal with a finite period is input and the pseudo white signal is obtained for a closed loop system formed due to reflection due to impedance mismatch in the means. The gain margin value is estimated based on the attenuation characteristic of the envelope component of the impulse response signal of the closed loop system estimated from the obtained cross-correlation value, and the amount of insertion loss is adjusted by calculating the excess or deficiency relative to the desired gain margin value. Therefore, the gain margin of the closed loop system until howling occurs can be maintained at a desired value, and stable call quality can be maintained without causing howling. In addition, since the amount of insertion loss is not increased more than necessary, the feasibility of two-way simultaneous call performance is increased, and the pseudo white signal is used to estimate the gain margin, so that the user is not audible. In addition, the synchronization control unit controls the transmission timing of the pseudo white signal, the synchronous addition averaging unit performs the moving average process synchronized with the pseudo white signal, and the synchronous addition averaging unit Since the envelope component is extracted from the output signal by the envelope detector, even when the level of stationary ambient noise existing in the closed loop is large, the effect of ambient noise is reduced and the gain margin value is obtained with sufficient accuracy. Estimated and insertion loss can be set to an appropriate value, so that a stable call can always be realized, and the ambient noise level during closed loop during the gain margin estimation process Even in such a case, the pseudo white signal transmission level and the number of synchronous additions are adjusted to adapt to this, so even if the ambient noise level fluctuates, the gain margin can be accurately tracked. The value can be estimated.

  Before describing an embodiment of the present invention, the configuration and operation of a loudspeaker described in Patent Document 1 serving as a base will be described in detail.

As described in the prior art, the loudspeaker described in Patent Document 1 includes a microphone 1 that outputs a collected sound as a voice signal on the transmission side (hereinafter referred to as a transmission signal), and a microphone 1. A first amplifier 2 that amplifies the transmitted signal, a speaker 3 that rings in response to a voice signal on the receiving side (hereinafter referred to as a received signal), and a second that amplifies the received signal output to the speaker 3. A predetermined amount in the amplifier 4, the hybrid circuit 5 as 2-4 line conversion means for performing 2-4 line conversion between the transmission side and reception side and the external communication line, and the signal path on the transmission side and reception side Attenuators (attenuators) 6 ₁ , 6 ₂ , a controller 7 for variably controlling the loss amounts of the attenuators 6 ₁ , 6 ₂ , and a response to the sample signal sent to the signal path Depending on the signal, microphone 1 and speaker 3 and an insertion loss amount adjusting means 8 for adjusting the loss amount based on the estimation result via the controller 7 while estimating the gain margin in the closed-loop system formed through 3.

  On the other hand, the insertion loss amount adjusting means 8 includes an impulse signal generator 9 for sending an impulse signal as a sample signal to the signal path on the reception side, an adder 10 for adding the impulse signal to the reception signal, and a response signal for the impulse signal. An envelope detector 11 for detecting an envelope, and a closed loop gain margin estimation unit 12 for estimating a gain margin in a closed loop system based on an output signal of the envelope detector 11, are configured by a microcomputer, a DSP (Digital Signal Processor), or the like. Is done. Here, the closed loop gain margin estimation unit 12 compares the output signal level of the envelope detector 11 with a previously obtained threshold level as described later, and calculates the gain margin value of the closed loop system based on the comparison result. And a determination unit 14 for estimation. The impulse signal used as the sample signal may be a single pulse signal with a sufficiently short pulse width. The envelope detector 11 can be composed of a synthesis circuit of a rectifier circuit and a low-pass filter circuit, a digital circuit such as a cyclic low-pass filter and a leak integrator, or a signal processing means such as a DSP (Digital Signal Processor).

Further, as shown in FIG. 19, the second amplifier 4 → speaker 3 → microphone 1 → first amplifier 2 → attenuator 6 ₁ → hybrid circuit 5 → attenuator 6 ₂ → insertion loss amount adjusting means 8 → second A closed loop is formed by the amplifier 4. Here, the transfer function in each part is defined as follows.

S: Electromechanical conversion characteristic of speaker 3 G: Acoustic transfer characteristic from speaker 3 to microphone 1 M: Acoustoelectric conversion characteristic of microphone 1 Kr: Amplification characteristic of second amplifier 4 Kx: Amplification characteristic of first amplifier 2 Ar: damping characteristics of the receiving side of the attenuator 6 ₂ Ax: attenuation characteristic of the attenuator ₆₁ of the transmitter side gamma: reflection transfer function in the hybrid circuit 5 also an impulse signal outputted from the impulse signal generator 9 P, The far-end speaker voice input signal transmitted from the external telephone line is Y (hereinafter referred to as “received signal”), and the sum of the near-end talker voice signal collected by the microphone 1 and the ambient noise is X ( (Hereinafter referred to as “acoustic signal”), the output signal (response signal) Q of the adder 10 which is one of the components of the insertion loss amount adjusting means 8 is expressed by the following equation.

  In the above equation, L (s) represents a one-round transfer function in the closed loop system, and s represents a Laplace variable.

Here, the stability of the closed-loop system can be discriminated by the one-round transfer function L (s). That is, the r component (= | L () at all frequencies where the θ component (= ∠L (s)) of the circular transfer function L (s) in the polar coordinate system is ∠L (s) = 2nπ (n is an integer). If s) |) is | L (s) | <1, the closed loop system is stable, and if there is a frequency where | L (s) | ≧ 1, the closed loop system becomes unstable and oscillates at that frequency and howling occurs. Arise. Further, when the closed loop system is stable, if the maximum gain value at all frequencies where ∠L (s) = 2nπ is L _MAX , the gain margin value of the closed loop system is expressed by 1 / L _MAX. . Therefore, a measure of the stability of the closed loop system can be evaluated by the closed loop gain margin value.

  On the other hand, the closed loop gain margin value has a close relationship with the impulse response characteristic of the closed loop system. The larger the closed loop gain margin value, the more rapidly the amplitude of the impulse response signal Q attenuates with time, and the smaller the closed loop gain margin value, the more attenuated. Becomes moderate. Accordingly, the closed loop gain margin estimation unit 12 observes the response signal Q when the sample signal (impulse signal) P for estimating the closed loop gain margin value is applied to the closed loop system, and the envelope signal component of the response signal Q is observed. Information on the time constant of the closed loop system is extracted to estimate the closed loop gain margin value up to the howling occurrence limit in the closed loop system, and based on the estimation result, the insertion loss amount adjusting means 8 is used to estimate the desired closed loop gain margin value. Calculate the amount of insertion loss to the closed loop system by calculating the excess and deficiency of the actual amount of insertion loss.

That is, since the time characteristic of the envelope component of the response signal Q obtained by the envelope detector 11 as described above has the property that the larger the closed loop gain margin value, the faster the attenuation and the smaller the attenuation, the slower the attenuation. A threshold level is obtained from the output data of the envelope detector 11 for various gain margin values learned in advance by the closed loop gain margin estimation unit 12, and the output signal level of the envelope detector 11 observed by the comparator 13. Is compared with the threshold level, the determination unit 14 can estimate the closed-loop gain margin based on the comparison result. Then, from the estimation result, a signal is transmitted to the controller 7 and the attenuators 6 ₁ , 6 are transmitted by the controller 7 in order to insert a loss amount necessary for setting the closed loop gain margin value to a value determined by the design specifications. The attenuation of ₂ is adjusted.

  As described above, in the loudspeaker, the gain margin value in the closed loop system is estimated from the response signal to the impulse signal, the difference between the estimated gain margin value and the target gain margin value is calculated, Since the insertion loss amount adjusting means 8 for adjusting the loss amount inserted into the signal path based on the calculation result is provided, the insertion loss amount is controlled according to the stability of the closed loop system even during a call, and the gain margin is always obtained. The value can be maintained at a value determined by the specification, and stable call quality can be maintained without causing howling. Moreover, since it is not necessary to increase the amount of insertion loss more than necessary as compared with the conventional example, there is an advantage that the possibility of realizing bidirectional simultaneous call performance is increased.

  Although the impulse signal generator 9 is used as the sample signal generator in the basic configuration and each of the embodiments described later, a burst signal may be used as the sample signal by using a burst signal generator instead. In this case, the transient response of the closed loop system from the moment when the transmission is stopped from the state in which the signal is transmitted is observed, and information on the time constant of the closed loop system is extracted from the envelope component. Thus, even when a burst signal is used as the sample signal, if the signal transmission time is sufficiently shorter than the delay time of the closed loop system, information on the time constant of the closed loop system is extracted from the envelope component of the response waveform. In addition, there is an advantage that by setting the signal transmission time of the burst signal to an appropriate value, it is possible to eliminate a sense of incongruity during the call and to suppress deterioration in call quality due to the transmission of the sample signal. However, as in the case of the impulse signal, it is necessary to obtain threshold levels for various gain margin values.

  In the above basic configuration, the gain margin value is estimated from the response signal Q expressed by Equation 1, but as is clear from Equation 1, the response signal Q includes a response signal (formula 1 except for the first term on the right side of 1). Therefore, when the level of the received signal Y and the sound signal X collected by the microphone 1 is large and the second term and the third term on the right side of Equation 1 cannot be ignored, it is difficult to accurately estimate the gain margin value. .

  Therefore, in each embodiment of the present invention, by extracting only the signal corresponding to the sample signal of the response signal Q represented by Expression 1 (the first term on the right side of Expression 1), other signals (Expression 1 The second term and the third term on the right side) are sufficiently suppressed so that the gain margin value can be estimated with high accuracy.

  FIG. 1 is a block diagram showing a main configuration of the insertion loss amount adjusting means 8 in the present embodiment. In addition, since the whole structure of the loudspeaker of this embodiment is common with the above-mentioned basic example, illustration and description are abbreviate | omitted and the same code | symbol is attached | subjected about a common part.

  As shown in FIG. 1, in addition to the impulse signal generator 9, the adder 10, the envelope detector 11, and the closed loop gain margin estimation unit 12, the insertion loss amount adjusting means 8 in the present embodiment includes impulses at predetermined time intervals. A synchronization control unit 15 that performs timing control for sending an impulse signal from the signal generator 9 to the signal path a plurality of times, and an impulse that is provided in the preceding stage of the envelope detector 11 and receives timing information from the synchronization control unit 15 And a synchronous addition averaging unit 16 for performing a synchronous addition averaging process on the response signal Q to the signal.

FIG. 2 is a block diagram showing the synchronization control unit 15 and the synchronization addition averaging unit 16. Synchronization control section 15, a predetermined time interval T _1, as shown in FIG. _{3, T 2, ..., T} N-1 impulse signal to be excited more than once every (sample _{signal) P 0, P 1, ...} , P _N-1 (hereinafter referred to as {P}) is sent from the impulse signal generator 9 and a synchronous signal synchronized with the transmission of the impulse signals P ₀ ... Is sent to the synchronous addition averaging unit 16 as shown in FIG. Output.

On the other hand, as shown in FIG. 2, the synchronous addition averaging unit 16 is turned on / off by the synchronization signal from the synchronization control unit 15, and the response of the impulse signal {P} input through the switch element 16a. a delay unit 16b ₁ ~16b _N-1 for delaying the signal {Q} predetermined time, the adder 16c ₁ ~16c _N-1 for adding the outputs of the delay units 16b ₁ ~16b _N-1, the total delay And a divider 16d that divides the sum of the output signals of the devices 16b _{1 to} 16b _N-1 (the output of the adder 16c _N-1 ) by the number N of synchronous additions, and adds and averages in synchronization with the impulse signal {P} Processing is performed to obtain a moving average of the response signal {Q}. Thus, the phase of the acoustic signal X and the reception signal Y is not related to the time intervals T ₁ , T ₂ ,..., T _{N-1 at} which the impulse signal {P} is transmitted. To suppress the second term and the third term on the right side in Equation 1 and emphasize only the response component for the impulse signal {P} in the first term on the right side. Only the response component can be extracted. When the moving average of the response signal {Q} is obtained, the delay signals 16b _{1 to} 16b _N−1 of the synchronous addition averaging unit 16 are reset by the reset signal output from the synchronous control unit 15, and the synchronous addition average is obtained. The unit 16 newly returns to the initial state where the moving average can be calculated.

Then, the moving average of the response signal {Q} output from the synchronous addition averaging unit 16 is input to the envelope detector 11, and the envelope of the closed loop response signal with respect to the impulse signal {P} obtained by the synchronous addition averaging process Line components are extracted. Further, the closed loop gain margin estimation unit 12 estimates a gain margin value from the attenuation characteristic of the envelope component extracted by the envelope detector 11 with respect to the time axis, and a required insertion loss amount based on the estimated gain margin value. Is calculated. Note that the time intervals T ₁ , T ₂ ,..., T _N-1 of the impulse signal {P} need to be sufficiently larger than the response time τ required for the gain margin value estimation process. Further, the observation time T (= T ₀ + T ₁ +... + T _N-1 + τ) of the output signal of the adder 11 required for the process of estimating the gain margin value can ignore the fluctuations in the characteristics of the closed loop system within this time T. It needs to be as short as possible.

  As described above, the synchronization control unit 15 and the synchronization addition averaging unit 16 are added to the insertion loss amount adjusting means 8 having the basic configuration, and the moving average of the response signal {Q} with respect to the impulse signal {P} is obtained. Since the average is output to the envelope detector 11, the influence of the ambient noise on the response signal {Q} is reduced and the gain margin value is accurate even when ambient noise and voice signals are present in the closed loop. It can be estimated well. As a result, even in the above case, the closed-loop system can be stabilized by setting the insertion loss amount to an appropriate value. In particular, this method is particularly effective when the ambient noise existing in the closed loop has a wide frequency band and the autocorrelation is small.

  In the configuration shown in FIG. 1, a sample signal (impulse signal or burst signal) is given to the system in order to estimate the gain margin value of the closed loop system. Since it can be heard, there is a risk of giving the user unpleasant discomfort.

  Therefore, if the gain margin value is estimated using a pseudo white signal instead of using a sample signal that may cause an unpleasant sensation such as an impulse signal or a burst signal, the above unpleasant sensation on the audibility described above can be obtained. Can be prevented.

  FIG. 4 is a block diagram showing another main configuration of the insertion loss amount adjusting means 8 of the present embodiment. The pseudo white signal generator 24 inserts a pseudo white signal having a finite period into the signal path, and the audio signal is simulated. An adder 10 for adding a white signal; a cross-correlation calculating unit 25 that calculates a cross-correlation value of a pseudo-white signal and a response signal to the pseudo-white signal and estimates a closed-loop impulse response based on the calculated cross-correlation value; An envelope detector 11 for detecting the envelope of the closed-loop impulse response signal estimated by the cross-correlation calculator 25, and a closed-loop gain margin estimator for estimating the gain margin in the closed loop based on the output signal of the envelope detector 11 12. In addition, the same code | symbol is attached | subjected about the part which is common in what was shown in FIG. 1, and detailed description is abbreviate | omitted.

Here, for example, an M-sequence signal is used as the pseudo white signal. The M-sequence signal means that f (x) in the following equation is a primitive polynomial of mod 2
f (x) = 1 + c ₁ x + c ₂ x ² +... c _p x ^p
Represented by sequence a _t on mod2 generated by the following equation.

a _t = c ₁ a _t-1 + c ₂ a _t-2 +... + c _p a _tp
The period T is 2 ^p −1. If the signal p (t) sent to the signal path is an M-sequence signal and its period T is sufficiently long, the following equation holds for the M-sequence signal p (t).

Here, Ψ _pp represents the autocorrelation value of the M-sequence signal p (t). However, since the autocorrelation value of the M-sequence signal does not depend on time, it can be expressed as the following equation.

Ψ _pp (t, t + τ) ＝ Ψ _pp (τ)
In the cross-correlation calculating unit 25, a value obtained by normalizing the cross-correlation value between the M-sequence signal p (t) and the output signal (response signal) q (t) of the adder 10 with the above-described A is obtained.

Here, the output signal q (t) of the adder 10 is expressed by the following equation.

However, h _p (σ), h _y (σ) and h _x (σ) are the impulse response of the closed loop system from the input point of the M-sequence signal p (t) to the output point of the adder 10, respectively, The closed loop impulse response from the input point to the output point of the adder 10 and the closed loop impulse response from the input point of the transmission signal X to the output point of the adder 10 are shown. Substituting Equation 4 into Equation 3 yields:

The above equation 5 can be transformed as the following equation.

Where ψ _py and ψ _px represent the cross-correlation value between the M-sequence signal p (t) and the received signal Y, and the cross-correlation value between the M-sequence signal p (t) and the transmitted signal X, respectively. Given.

Here, since the M-sequence signal p (t) and the received signal Y, and the M-sequence signal p (t) and the transmitted signal X are not causal to each other, the respective cross-correlation values ψ _py and ψ _px are the time t. Varies depending on When the period T of the M-sequence signal p (t) is sufficiently long, the cross-correlation values ψ _py and ψ _px are zero. Therefore, in this case, the second term and the third term on the right side of Equation 6 are zero and can be transformed as the following equation.

Therefore, the value obtained by normalizing the cross-correlation value between the M-sequence signal (pseudo white signal) p (t) given by Ψ _pp (t, t + τ) = Ψ _pp (τ) and the response signal q (t) by A. Is obtained, the coefficient in the delay time τ of the impulse response of the system from the M-sequence signal p (t) to the response signal q (t) can be obtained. However, the above equation 9 holds when the period T of the M-sequence signal p (t) is sufficiently long that the cross-correlation values ψ _py and ψ _px given by the equations 7 and 8 can be regarded as zero. In the other cases, the second term and the third term on the right-hand side of Equation 6 above become disturbance components, which are factors that degrade the estimation accuracy of the impulse response.

By the way, when the cross-correlation calculation unit 25 is realized by a digital circuit, the cross-correlation value obtained by normalizing the above Ψ _pp (t, t + τ) = Ψ _pp (τ) with the above A is expressed by the following equation.

Here, I represents the period of the M-sequence signal p (t) in the discrete time system, and p (i) and q (i + j) are the M-sequence signal p (t) and the response signal q at the sample times i and i + j, respectively. Represents the data of (t). Further, the value obtained by the above equation 7 is one coefficient h _p (j) of the impulse response of the system from the M-sequence signal p (t) to the response signal q (t), and is used to estimate the gain margin of the closed loop system. If the impulse response observation time required for the above is sample time J, it is necessary to obtain a total of J coefficients of h _p (0), h (1), h (2),..., H (J−1). Therefore, in order to estimate the impulse response of the system from the M-sequence signal (pseudo white signal) p (t) to the response signal q (t), I × J product-sum operations are required.

  The impulse response (response signal Q) of the system from the pseudo white signal p (t) to the response signal q (t) obtained by the arithmetic processing as described above is input to the envelope detector 11 and the closed loop gain margin estimation unit 12 The gain margin value is estimated from the attenuation characteristic of the envelope component extracted by the envelope detector 11 with respect to the time axis, and the required insertion loss amount is calculated based on the estimated gain margin value.

  As described above, the pseudo white signal generator 24 is added in place of the impulse signal generator 9 to the insertion loss amount adjusting means 8 of the basic configuration, and the cross correlation between the pseudo white signal and the response signal to the pseudo white signal is added. A cross-correlation calculating unit 25 that obtains a value and estimates a closed-loop impulse response based on the cross-correlation value is added, and the envelope detector 11 and the closed-loop gain margin estimating unit 12 gain from the estimated impulse response (response signal). Since the margin value is estimated, the gain margin value can be accurately estimated without giving the user unpleasant discomfort, and the closed loop system can be stabilized by setting the insertion loss amount to an appropriate value.

  FIG. 5 is a block diagram showing still another main configuration of the insertion loss amount adjusting means 8 in the present embodiment. The synchronization control unit 15 and the synchronous addition average in the configuration shown in FIG. 1 with respect to the configuration shown in FIG. The feature is that the portion 16 is provided.

In this configuration, when the period of the pseudo white signal transmitted to the signal path is not sufficiently long and the second term and the third term on the right side of Equation 6 are not regarded as zero and become a disturbance element, a synchronous addition averaging process is performed. Therefore, these effects are reduced and the estimation accuracy of the impulse response of the closed loop system is improved. Now, assuming that the period of the M-sequence signal p (t) is T ₁ and the number of synchronous additions is N, the output value of the synchronous addition averaging unit 16 is expressed by the following equation.

Substituting Equations 6 and 9 into Equation 11 above and rearranging results in the following equation.

Here, since the cross-correlation values Ψ _py and Ψ _px fluctuate irregularly with respect to time t, the second term and the third term on the right side in the above equation 12 are suppressed by sufficiently increasing the value of the number of times of synchronous addition N. be able to.

  According to this configuration, the period T of the M-sequence signal p (t) transmitted to the signal path can be shortened as compared with the configuration shown in FIG. 4, so that the insertion loss amount adjusting means 8 is realized by a digital circuit. In this case, there is an advantage that the capacity of the storage device and the number of product sums required for the generation of the M-sequence signal p (t) and the calculation of Equation 10 can be reduced. The closed loop impulse response (response signal) output from the synchronous addition averaging unit 16 is input to the envelope detector 11, and the required insertion loss amount is calculated by the same arithmetic processing as the configuration shown in FIG. The

(Embodiment 1)
FIG. 6 is a block diagram showing the insertion loss amount adjusting means 8 according to the first embodiment of the present invention, which is characterized in that a convergence determining unit 17 is provided in the configuration shown in FIG.

After the gain margin value estimation process is started, the signal Q _M '(t) output from the synchronous addition averaging unit 15 after the Mth impulse signal P _M-1 is sent to the closed loop is expressed by the following equation. However, 0 ≦ t ≦ τ, and t = 0 represents the moment when the _Mth impulse signal P _M-1 is sent to the closed loop system.

Further, a signal Q _{M + 1} ′ (t) output from the synchronous addition averaging unit 16 after sending the M + 1-th impulse signal P _M is expressed by the following equation.

Here, the convergence determination unit 17 constantly monitors the output signal Q ′ (t) of the synchronous addition averaging unit 16, and the signal Q _{M + 1} ′ (t) obtained by the _{M +} 1th synchronous addition averaging process and the previous time. It is determined whether the difference from the signal Q _M ′ (t) obtained by the synchronous addition averaging process has converged within a certain range. That is, the convergence criterion is given by the following equation.

  The above equation can be transformed into the following equation using equation 14.

  From the above equation, in order to satisfy the convergence condition of Equation 15, α is sufficiently small (that is, the number of times of synchronous addition M is sufficiently large), and the output signal Q ′ (t) of the synchronous addition averaging unit 16 responds. It can be seen that it is necessary to converge to the expected value E [Q (t)] of the signal Q (t).

  Thus, the convergence determination unit 17 updates the synchronization addition process until the convergence of the output signal Q ′ (t) of the synchronization addition averaging unit 16 is confirmed, and when the convergence is confirmed, the convergence determination unit 17 passes the synchronization control unit 15. Thus, the synchronous addition processing in the synchronous addition averaging unit 16 is interrupted and the transmission of the impulse signal {P} from the impulse signal generator 9 is stopped. The output signal Q '(t) of the synchronous addition averaging unit 16 is input to the envelope detector 11, and the required insertion loss amount is calculated by the same processing as in the configuration shown in FIG.

  As described above, in the present embodiment, the synchronization control unit 15 determines continuation / interruption of the synchronization addition process in the synchronization addition averaging unit 16 according to the determination result of the convergence determination unit 17. When the ambient noise does not exist even when ambient noise exists in the closed loop by continuing the transmission of the impulse signal {P} and the synchronous addition process until the output signal Q ′ (t) converges to a constant value. It is possible to estimate the gain margin value with the same degree of accuracy. In addition, even if the convergence determination part 17 is provided with respect to the structure shown in FIG. 5, there can exist the same effect.

(Embodiment 2)
FIG. 7 is a block diagram showing the insertion loss amount adjusting means 8 in the second embodiment of the present invention, which is characterized in that a timer unit 18 is provided in the first embodiment.

The timer unit 18 is reset by the synchronization control unit 15 at the same time as the first impulse signal P ₀ is sent from the impulse signal generator 9 and measures the elapsed time thereafter. A signal indicating the elapsed time is input from the timer unit 18 to the synchronization control unit 15 at any time. In the synchronization control unit 15, even if the elapsed time exceeds a predetermined time, the convergence determination unit 17 outputs the synchronization addition averaging unit 16. If the convergence of the signal Q ′ (t) is not confirmed, a reset signal is output to the synchronous addition averaging unit 16 to interrupt the gain margin estimation process, and the impulse signal {P} is transmitted from the impulse signal generator 9. Stop. Thus, in the case where the closed loop system fluctuates during transmission of the impulse signal {P} and the output signal Q ′ (t) does not converge even if the synchronous addition processing is performed for a long time, the synchronous addition averaging processing is performed. By resetting once, it is possible to quickly estimate the gain margin value after the closed-loop system fluctuates.

  As described above, according to the present embodiment, the characteristics of the closed loop system change during the gain margin value estimation process, and the output of the synchronous addition averaging unit 16 even if the elapsed time measured by the timer unit 18 exceeds a predetermined time. When the signal Q ′ (t) does not converge, the process of estimating the gain margin value of the closed loop system after the change can be started quickly by interrupting and resetting the synchronous addition process once. In addition, even if the timer unit 18 is provided together with the convergence determination unit 17 in the configuration shown in FIG.

(Embodiment 3)
FIG. 8 is a block diagram showing the insertion loss amount adjusting means 8 according to the third embodiment of the present invention, which is characterized in that an autocorrelation function calculation unit 19 is provided in the configuration shown in FIG.

The autocorrelation function calculation unit 19 calculates an autocorrelation function of a signal existing in the closed loop before sending the impulse signals P ₀ . Here, if the signal existing in the closed loop before sending the impulse signals P ₀ ... Is r (t) and the autocorrelation function is R (τ), the autocorrelation function R (τ) is expressed by the following equation. Is done.

Here, the response signal {Q} to the impulse signal {P} is represented by the sum of the response component to the impulse signal P ₀ ... And the signal r (t) (noise component) originally present in the closed loop. Accordingly, the relationship between the time shift amount τ and the number of times of synchronization addition N necessary for obtaining a noise component suppression amount equal to or greater than a predetermined value is examined in advance, and the synchronization control unit 15 determines the relationship and the autocorrelation function. By comparing with the autocorrelation function R (τ) obtained by the calculation unit 19, an impulse signal {for minimizing the time T (= T ₀ + T ₁ +... + T _N-1 + τ) required for the synchronous addition process { The transmission interval T _n (n = 0, 1,..., N−1) and the number N of synchronous additions can be obtained. As a result, the time required to estimate the gain margin value can be shortened.

As described above, in the present embodiment, the auto-correlation function calculating unit 19 that calculates the auto-correlation function R (τ) of the signal r (t) existing in the closed loop is provided in the insertion loss amount adjusting unit 8, and the calculated self Since the synchronization control unit 15 adjusts the transmission interval T _n of the impulse signal {P} from the impulse signal generator 9 and the number N of synchronization additions in the synchronization addition averaging unit 16 based on the correlation function R (τ). From the autocorrelation function R (τ) of the signal r (t) existing in the closed loop calculated in advance, the transmission interval T _n and the synchronization of the impulse signal {P} so as to minimize the time T required for the synchronous addition process The gain margin value estimation process can be speeded up by adjusting the number N of additions. In addition, even if the autocorrelation function calculation unit 19 is provided in the configuration shown in FIG.

(Embodiment 4)
FIG. 9 is a block diagram showing the insertion loss amount adjusting means 8 according to the fourth embodiment of the present invention, in which a noise level estimation unit 20 and an impulse signal transmission level adjustment unit 21 are provided in the configuration shown in FIG. There is a feature.

The noise level estimation unit 20 estimates the level of ambient noise existing in the closed loop before the impulse signal {P} is sent to the closed loop system, and the impulse signal transmission level adjustment unit 21 estimates the ambient noise. The level of the impulse signals P ₀ ... Output from the impulse signal generator 9 is adjusted in accordance with the level of. That is, in the gain margin value estimation process according to the present invention, the ratio of the impulse signal transmission level to the ambient noise level in the closed loop (this ratio is defined here as the S / N ratio) is the gain margin value estimation accuracy. Therefore, the noise level estimation unit 20 estimates the ambient noise level before the impulse signal P ₀ ... Is sent to the closed loop, and the S / N ratio is greater than or equal to a predetermined value with respect to the estimated ambient noise level. By adjusting the transmission level of the impulse signals P ₀ ... By the impulse signal transmission level adjusting unit 21 so that the following can be obtained, it is possible to improve the estimation accuracy of the gain margin value.

  As described above, in this embodiment, the noise level estimation unit 20 that estimates the level of ambient noise existing in the closed loop, and the transmission level of the sample signal (impulse signal) are adjusted based on the estimation result by the noise level estimation unit 20. Since the insertion loss amount adjusting unit 8 is provided with the impulse signal transmission level adjusting unit 21 that performs the above operation, the level of the impulse signal transmitted to the closed loop system is set to a sufficient level with respect to the ambient noise level. The response signal {Q} to the impulse signal {P} can be obtained with a high S / N ratio, and the estimation accuracy of the gain margin value can be improved. It is to be noted that the same effect can be obtained by providing the noise level estimation unit 20 and means for adjusting the transmission level of the pseudo white signal in the configuration shown in FIG.

(Embodiment 5)
FIG. 10 is a block diagram showing the insertion loss amount adjusting means 8 in Embodiment 5 of the present invention, in that a noise level estimating unit 20 and a synchronous addition number adjusting unit 22 are provided in the configuration shown in FIG. There are features.

  Similarly to the fourth embodiment, the noise level estimation unit 20 estimates the level of ambient noise existing in the closed loop before sending the impulse signal {P} to the closed loop system. The number of synchronous additions N in the synchronous addition averaging unit 16 is adjusted according to the estimated level of ambient noise. Generally, in order to suppress the ambient noise when the ambient noise level is high, it is necessary to set the number of synchronization additions N to a large value. Conversely, when the ambient noise level is low, even if the number of synchronization additions N is small. Ambient noise can be suppressed.

  Thus, the statistical properties of the ambient noise level and the number of synchronous additions are quantitatively examined in advance, and the synchronous addition number adjusting unit 22 is used for the ambient noise level estimated by the noise level estimating unit 20. By setting the necessary minimum number N of synchronous additions, the delay time associated with the average of synchronous additions can be minimized.

  As described above, in the present embodiment, the noise level estimation unit 20 that estimates the level of ambient noise existing in the closed loop, and the synchronization addition number N in the synchronization addition averaging unit 16 based on the estimation result by the noise level estimation unit 20 are calculated. Since the synchronization loss number adjusting unit 22 to be adjusted is provided in the insertion loss amount adjusting means 8, the synchronization addition number N can be set to the minimum necessary according to the level of ambient noise existing in the closed loop system. The calculation time required for the addition process can be minimized. In addition, by minimizing the number of times a sample signal (impulse signal) is sent for one gain margin estimation process, it is possible to reduce auditory discomfort and discomfort due to the impulse signal being heard superimposed on the received signal. can do. In addition, even if the noise level estimation unit 20 and the synchronous addition number adjustment unit 22 are provided in the configuration shown in FIG.

(Embodiment 6)
FIG. 11 is a block diagram showing the insertion loss amount adjusting means 8 according to the sixth embodiment of the present invention. The noise level estimating unit 20, the impulse signal transmission level adjusting unit 21, and the number of times of synchronous addition are adjusted with respect to the configuration shown in FIG. The feature is that the unit 22 and the ambient noise extraction unit 23 are provided. However, at least one of the impulse signal transmission level adjusting unit 21 and the synchronous addition number adjusting unit 22 may be provided. Further, since the noise level estimation unit 20, the impulse signal transmission level adjustment unit 21, and the synchronous addition number adjustment unit 22 are common to the fourth and fifth embodiments, the description thereof is omitted.

  As is clear from Equation 1, the response signal q observed during transmission of the impulse signal {P} to the closed loop includes a response component for the impulse signal {P} and an ambient noise component (and transmission / reception voice component). It is mixed. Therefore, the ambient noise extraction unit 23 extracts only the ambient noise component from the signal on which the plurality of signal components are superimposed, and estimates the ambient noise level from the extracted component, whereby the gain after transmission of the impulse signal {P} is obtained. Even during the margin value estimation process, the impulse signal transmission level and the number of synchronous additions N can be adaptively adjusted according to the level of ambient noise.

The ambient noise extraction unit 23 is reset when a synchronization signal synchronized with the transmission timing of the impulse signal P _k (k = 0, 1,..., N−1) is input from the synchronization control unit 15 as shown in FIG. Between the timer circuit 23a and the elapsed time t _k (elapsed time since each impulse signal P _k is sent to the closed loop system) measured by the timer circuit 23a and the response time τ of the closed loop system with respect to the impulse signal P _k A determination unit 23b that performs the determination, and a multiplier 23c that multiplies the closed-loop response signal Q by the output signal of the determination unit 23b. Here, the output signal of the multiplier 23 c is input to the noise level estimation unit 20. The determination unit 23b outputs 1 when it is determined that the elapsed time t _k measured by the timer circuit 23a is larger than the response time τ (t _k > τ), and the elapsed time t _k is longer than the response time τ. If it is determined to be small (t _k <τ), 0 is output.

That is, in a time period (τ <t _k <T _{k + 1} ) in which the elapsed time t _k after sending the impulse signal P _k to the closed loop system is larger than the response time τ and smaller than the sending interval T _{k + 1} . Can ignore the response component (the first term on the right side in Equation 1) with respect to the impulse signal P _k included in the response signal Q, and the output signal (response signal) Q of the adder 10 in the time zone satisfying τ <t _k Since the noise component (and the component for the transmission / reception voice signal) becomes dominant, as described above, when the elapsed time t _k is longer than the response time τ (t _k > τ), the response signal Q is directly estimated as the noise level. When the elapsed time t _k is equal to or shorter than the response time τ (t _k <τ), the signal is not output to the noise level estimation unit 20 so that the ambient noise extraction unit 23 outputs an impulse signal { Watch while sending P} Is the it is possible to extract the ambient noise component than the response signal q.

Then, the noise level estimation unit 20 estimates the ambient noise level from the extracted ambient noise components, and based on the estimated value, at least one of the impulse signal transmission level adjustment unit 21 and the synchronous addition number adjustment unit 22 is used. Adjustment (setting) of the transmission level of the impulse signal and the number N of synchronous additions is performed. It should be noted that it is desirable to stop the noise level estimation processing in the noise level estimation unit 20 in a time zone in which the ambient noise extraction unit 23 does not extract ambient noise (a time zone satisfying t _k ≦ τ).

  As described above, according to the present embodiment, since the ambient noise extraction unit 23 that extracts the ambient noise signal from the signal transmitted during the closed loop is provided in the insertion loss amount adjusting unit 8, the gain margin value estimation process is performed. Even when the ambient noise level in the closed loop changes, at least one of the transmission level of the impulse signal {P} and the number of times of synchronous addition N is adjusted to adapt to this, so that the ambient noise level varies. Even in this case, the gain margin value can be accurately estimated following this. It is to be noted that the same effect can be obtained even if the noise level estimation unit 20, the impulse signal transmission level adjustment unit 21, the synchronous addition number adjustment unit 22, and the ambient noise extraction unit 23 are provided in the configuration shown in FIG. .

In time and, although the above embodiments have been estimated gain margin value of the closed loop by observing the slope of the envelope of the response signal when the transmitted sample signal (impulse signal or burst signals) in a closed loop system There is an upper limit to the estimated gain margin value. In other words, when the gain margin value of the closed loop system is greater than or equal to a predetermined value (the slope of the envelope of the response signal with respect to the impulse signal is steep and greater than the predetermined value), it is difficult to accurately determine the slope of the envelope. In addition, there is a possibility that the estimation accuracy of the gain margin value is also lowered. Such a tendency becomes more prominent as the level of a signal (speech signal or ambient noise signal) other than the sample signal transmitted through the closed loop system increases.

  As shown in FIG. 14, the slope of the envelope of the response signal when an impulse signal is added to the closed loop system composed of the microphone 1, the first amplifier 2, the speaker 3, and the second amplifier 4 The experimental results observed by adding signals (random noise) are shown in FIGS. Here, FIG. 15 shows a case where 20 dB random noise is added without performing the synchronous addition process, FIG. 16 shows a case where 20 dB random noise is added by performing the synchronous addition process, and FIG. The response signal waveforms when the random noise is added are shown, and curves i to c in each figure show the cases where the gain margin values of the closed loop system are 3 dB, 6 dB, and 10 dB, respectively. From these experimental results, the higher the level of random noise (signals other than the sample signal) (that is, curve B rather than curve A, curve C rather than curve B), it becomes more difficult to accurately determine the slope of the envelope. Obviously.

Therefore, in order to solve the above-described problem, an inclination determination unit 26 that determines the magnitude relationship between the inclination of the envelope detected by the envelope detector 11 and a predetermined value with respect to the configuration shown in FIG. It is desirable to add to the insertion loss amount adjusting means 8 a gain margin adjusting amplifier 27 that is inserted into the signal path of FIG.

Figure 13 is a block diagram showing an insertion loss amount adjusting means 8. The envelope component extracted by the envelope detector 11 is input to the slope judgment unit 26, and the slope of the envelope component can be accurately estimated by the closed-loop gain margin estimation unit 12 at the next stage. Whether or not it is determined by the inclination determination unit 26. Further, the gain margin adjusting amplifier 27 is inserted in the previous stage of the second amplifier 4, and the degree of amplification is varied by a control signal given from the inclination determining unit 26.

  Thus, the slope of the envelope component extracted by the envelope detector 11 is compared with a predetermined value by the inclination determination unit 26, and when it is determined that the inclination is smaller than the predetermined value, that is, can be estimated, the envelope The component is output to the closed-loop gain margin estimation unit 12 and the gain of the gain margin adjustment amplifier 27 is maintained at the initial value (= 1).

On the other hand, since the slope of the envelope curve is steep, when the slope determination unit 26 determines that the slope of the envelope component is larger than a predetermined value, that is, cannot be estimated, a control signal is output to adjust the gain margin. The gain of the amplifier 27 is increased. For example, when the estimable upper limit value is L _max [dB], it may be increased in steps from 0 [dB] to L _max [dB]. As a result, the gain margin value of the system is reduced by the gain of the gain margin adjusting amplifier 27. Therefore, if the gain of the gain margin adjusting amplifier 27 is set to an appropriate value, the gain margin of the system is estimated as a closed loop gain margin. The value can be estimated by the unit 12. Thereafter, the inclination of the envelope component extracted by the envelope detector 11 becomes small and it is determined that the inclination can be estimated by the inclination determination unit 26, and the envelope component is determined as the closed loop gain margin estimation unit 12. The gain margin is estimated.

  Here, since a value obtained by multiplying the gain margin value estimated by the closed-loop gain margin estimation unit 12 by the gain of the gain margin adjustment amplifier 27 becomes the actual gain margin value, the insertion loss is based on this value. It is necessary to adjust the amount.

As described above, the determined inclination judgment unit 26 the magnitude relation between the slope and the predetermined value of the envelope is detected by an envelope detector 11, the determination result by the inclination determination unit 26 is inserted in the signal path of the receiving side if and a gain margin adjusting amplifier 27 for changing the amplification factor in response to the insertion loss adjusting means 8 can also estimate the gain margin value precisely in the gain margin is large state of the closed loop system. As a result, the amount of insertion loss can be adjusted so that the gain margin value of the closed loop system can always be maintained at a sufficient value. In the above configuration , the gain margin adjusting amplifier 27 is inserted in the signal path on the transmission side, but it goes without saying that the same effect can be obtained even if it is inserted in the signal path on the reception side. Further, in the above configuration , the inclination determination unit 26 and the gain margin adjustment amplifier 27 are added to the configuration shown in FIG. 1, but the configuration shown in FIG. 4 or FIG. 5 or the basic configuration shown in FIG. On the other hand, the same effect can be obtained by adding the inclination determining unit 26 and the gain margin adjusting amplifier 27.

In addition, each insertion loss amount adjusting means 8 in the first to sixth embodiments can be realized by using a microcomputer or a DSP similarly to the basic configuration. Although the impulse signal is exemplified as the sample signal, it is needless to say that a burst signal may be used as the sample signal.

It is a block diagram which shows the main structures of the insertion loss amount adjustment means in embodiment. It is a block diagram which shows the synchronous control part and synchronous addition average part in the same as the above. It is explanatory drawing for demonstrating operation | movement same as the above. It is a block diagram which shows the other main structure of the insertion loss amount adjustment means in embodiment. It is a block diagram which shows the further another main structure of the insertion loss amount adjustment means in embodiment. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 1. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 2. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 3. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 4. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 5. It is a block diagram which shows the insertion loss amount adjustment means in Embodiment 6. It is a block diagram which shows the ambient noise extraction part in the same as the above. It is a block diagram which shows another structure of the insertion loss amount adjustment means in Embodiments 1-6 . It is explanatory drawing same as the above. It is explanatory drawing same as the above. It is explanatory drawing same as the above. It is explanatory drawing same as the above. (A) is a block diagram showing the basic configuration of the present invention, (b) is a block diagram showing the basic configuration of the insertion loss amount adjusting means. It is explanatory drawing for demonstrating the closed loop in the same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Insertion loss amount adjustment means 9 Impulse signal generator 10 Adder 11 Envelope detector 12 Closed loop gain margin estimation part 15 Synchronization control part 16 Synchronization addition average part 17 Convergence determination part

Claims (10)

A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion loss that estimates the gain margin in the closed loop formed through the microphone and speaker according to the control signal and the response signal to the sample signal sent to the signal path and adjusts the loss amount based on the estimation result via the control means And an insertion loss amount adjusting means for sending a sample signal to the signal path and a sample signal for the audio signal. In the closed loop based on the output signal of the envelope detector, and the envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path. A closed loop gain margin estimation unit for estimating a gain margin, a synchronization control unit for performing timing control for sending a sample signal from a sample signal generator to a signal path a plurality of times at predetermined time intervals, and a front stage of an envelope detector A synchronization addition averaging unit that receives the timing information from the synchronization control unit and performs a synchronous addition averaging process on the response signal with respect to the sample signal; and an autocorrelation function calculation unit that calculates an autocorrelation function of the signal existing in the closed loop ; comprising a synchronization control unit, and time shift amount is a variable of the autocorrelation function, synchronization necessary to obtain the suppression amount of the predetermined value or more of the noise component By comparing the relationship with the number of calculations with the autocorrelation function calculated by the autocorrelation function calculation unit, the sample signal transmission interval and the number of synchronization additions required to minimize the time required for the synchronous addition process are obtained. The loudspeaker is characterized by adjusting the transmission interval and the number of synchronous additions . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion loss that estimates the gain margin in the closed loop formed through the microphone and speaker according to the control signal and the response signal to the sample signal sent to the signal path and adjusts the loss amount based on the estimation result via the control means And an insertion loss amount adjusting means for sending a sample signal to the signal path and a sample signal for the audio signal. In the closed loop based on the output signal of the envelope detector, and the envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path. A closed loop gain margin estimation unit for estimating a gain margin, a synchronization control unit for performing timing control for sending a sample signal from a sample signal generator to a signal path a plurality of times at predetermined time intervals, and a front stage of an envelope detector A synchronous addition averaging unit that receives the timing information from the synchronization control unit and performs synchronous addition averaging processing on the response signal to the sample signal, a noise level estimation unit that estimates the level of ambient noise existing in the closed loop, and noise A synchronization addition number adjustment unit that adjusts the number of synchronization additions in the synchronization addition averaging unit based on the estimation result by the level estimation unit. The number-of-addition adjustment unit is a delay associated with the synchronous addition average with respect to the ambient noise level estimated by the noise level estimation unit based on the statistical properties of the ambient noise level and the number of synchronous additions that have been quantitatively examined in advance. expanding voice call machine characterized by comprising setting the minimum synchronous addition number required to minimize the time. The insertion loss adjustment means includes an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and the noise level estimation unit determines the ambient noise level existing in the closed loop from the extracted ambient noise signal. The loudspeaker according to claim 2, wherein the loudspeaker is estimated . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion loss that estimates the gain margin in the closed loop formed through the microphone and speaker according to the control signal and the response signal to the sample signal sent to the signal path and adjusts the loss amount based on the estimation result via the control means And an insertion loss amount adjusting means for sending a sample signal to the signal path and a sample signal for the audio signal. In the closed loop based on the output signal of the envelope detector, and the envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path. A closed loop gain margin estimation unit for estimating a gain margin, a synchronization control unit for performing timing control for sending a sample signal from a sample signal generator to a signal path a plurality of times at predetermined time intervals, and a front stage of an envelope detector A synchronous addition averaging unit that receives the timing information from the synchronization control unit and performs synchronous addition averaging processing on the response signal to the sample signal, a noise level estimation unit that estimates the level of ambient noise existing in the closed loop, and noise A transmission level adjustment unit that adjusts the transmission level of the sample signal based on the estimation result by the level estimation unit, and is transmitted during the closed loop An ambient noise extraction unit for extracting an ambient noise signal from the signal, the noise level estimation unit is configured by estimating the level of ambient noise existing in the closed loop from the ambient noise signal extracted by the ambient noise extraction unit, In the transmission level adjusting unit, the ratio of the sample signal transmission level to the ambient noise level in the closed loop is a predetermined value or more with respect to the ratio of the sample signal transmission level to the ambient noise level before the sample signal is transmitted to the closed loop. The loudspeaker is characterized by adjusting the transmission level of the sample signal as described above . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion loss that estimates the gain margin in the closed loop formed through the microphone and speaker according to the control signal and the response signal to the sample signal sent to the signal path and adjusts the loss amount based on the estimation result via the control means And an insertion loss amount adjusting means for sending a sample signal to the signal path and a sample signal for the audio signal. In the closed loop based on the output signal of the envelope detector, and the envelope detector for detecting the envelope of the response signal output from the adder when the sample signal is added to the signal path. A closed loop gain margin estimation unit for estimating a gain margin, a synchronization control unit for performing timing control for sending a sample signal from a sample signal generator to a signal path a plurality of times at predetermined time intervals, and a front stage of an envelope detector A synchronous addition averaging unit that receives timing information from the synchronization control unit and performs synchronous addition averaging processing on the response signal with respect to the sample signal, and an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during a closed loop A noise level estimator that estimates the level of ambient noise existing in the closed loop from the extracted ambient noise signal, and a noise level estimator. A transmission level adjustment unit that adjusts the transmission level of the sample signal based on the estimation result, and a synchronous addition number adjustment unit that adjusts the number of synchronous additions in the synchronous addition averaging unit based on the estimation result by the noise level estimation unit, The transmission level adjustment unit adjusts the ratio of the sample signal transmission level to the ambient noise level in the closed loop so that the ratio of the sample signal transmission level to the ambient noise level before the sample signal is transmitted to the closed loop is equal to or greater than a predetermined value. The synchronization addition number adjusting unit is estimated by the noise level estimation unit based on the statistical properties of the ambient noise level and the number of synchronization additions that have been quantitatively examined in advance. Set the minimum number of synchronous additions necessary to minimize the delay time associated with the synchronous average for the ambient noise level Expanding voice call machine said. A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion that estimates the gain margin in the closed loop formed through the microphone and the speaker and adjusts the loss amount based on the estimation result via the control means according to the control means and the response signal to the pseudo white signal sent to the signal path Loss amount adjusting means, and the insertion loss amount adjusting means includes a pseudo white signal generator for inserting a pseudo white signal having a finite period in the signal path, and an audio signal. An adder that adds a pseudo white signal, and a cross correlation value of the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path, and based on the obtained cross correlation value A cross-correlation operation unit that estimates the impulse response of the closed loop, an envelope detector that detects an envelope of the impulse response signal of the closed loop estimated by the cross-correlation operation unit, and a closed loop based on the output signal of the envelope detector A closed loop gain margin estimating unit for estimating a gain margin, a synchronous control unit for performing timing control for sending a pseudo white signal to a signal path from a pseudo white signal generator to a signal path at a predetermined time interval, and an envelope detector The closed-loop impulse response signal estimated by the cross-correlation calculation unit in response to timing information from the synchronization control unit A synchronous addition averaging unit that performs a periodical addition averaging process, and an autocorrelation function calculation unit that calculates an autocorrelation function of a signal existing in a closed loop, and the synchronization control unit includes a time shift amount that is a variable of the autocorrelation function, The time required for synchronous addition processing is minimized by checking the relationship between the number of synchronous additions necessary to obtain a noise component suppression amount equal to or greater than a predetermined value and the autocorrelation function calculated by the autocorrelation function calculation unit. A loudspeaker, wherein a transmission interval and the number of synchronous additions of a pseudo white signal from a pseudo white signal generator required for conversion are obtained, and the transmission interval and the number of synchronous additions are adjusted . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion that estimates the gain margin in the closed loop formed through the microphone and the speaker and adjusts the loss amount based on the estimation result via the control means according to the control means and the response signal to the pseudo white signal sent to the signal path Loss amount adjusting means, and the insertion loss amount adjusting means includes a pseudo white signal generator for inserting a pseudo white signal having a finite period in the signal path, and an audio signal. An adder that adds a pseudo white signal, and a cross correlation value of the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path, and based on the obtained cross correlation value A cross-correlation operation unit that estimates the impulse response of the closed loop, an envelope detector that detects an envelope of the impulse response signal of the closed loop estimated by the cross-correlation operation unit, and a closed loop based on the output signal of the envelope detector A closed loop gain margin estimating unit for estimating a gain margin, a synchronous control unit for performing timing control for sending a pseudo white signal to a signal path from a pseudo white signal generator to a signal path at a predetermined time interval, and an envelope detector The closed-loop impulse response signal estimated by the cross-correlation calculation unit in response to timing information from the synchronization control unit The synchronous addition averaging unit for performing the periodic addition averaging process, the noise level estimation unit for estimating the level of ambient noise existing in the closed loop, and the number of synchronous additions in the synchronous addition averaging unit based on the estimation result by the noise level estimation unit A synchronization addition number adjustment unit, and the synchronization addition number adjustment unit is configured to estimate the ambient level estimated by the noise level estimation unit based on the statistical properties of the ambient noise level and the number of synchronization additions that have been quantitatively examined in advance. A loudspeaker having a minimum number of synchronization additions required for minimizing a delay time associated with a synchronization addition average with respect to a noise level . The insertion loss adjustment means includes an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and the noise level estimation unit determines the ambient noise level existing in the closed loop from the extracted ambient noise signal. 8. The loudspeaker according to claim 7, wherein the loudspeaker is estimated . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion that estimates the gain margin in the closed loop formed through the microphone and the speaker and adjusts the loss amount based on the estimation result via the control means according to the control means and the response signal to the pseudo white signal sent to the signal path Loss amount adjusting means, and the insertion loss amount adjusting means includes a pseudo white signal generator for inserting a pseudo white signal having a finite period in the signal path, and an audio signal. An adder that adds a pseudo white signal, and a cross correlation value of the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path, and based on the obtained cross correlation value A cross-correlation operation unit that estimates the impulse response of the closed loop, an envelope detector that detects an envelope of the impulse response signal of the closed loop estimated by the cross-correlation operation unit, and a closed loop based on the output signal of the envelope detector A closed loop gain margin estimating unit for estimating a gain margin, a synchronous control unit for performing timing control for sending a pseudo white signal to a signal path from a pseudo white signal generator to a signal path at a predetermined time interval, and an envelope detector The closed-loop impulse response signal estimated by the cross-correlation calculation unit in response to timing information from the synchronization control unit Synchronous addition averaging unit that performs periodic addition averaging processing, noise level estimation unit that estimates the level of ambient noise existing in the closed loop, and transmission level that adjusts the transmission level of the pseudo white signal based on the estimation result by the noise level estimation unit An adjustment unit and an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and the noise level estimation unit exists in the closed loop from the ambient noise signal extracted by the ambient noise extraction unit The transmission level adjustment unit is configured by estimating the ambient noise level, and the ratio of the pseudo white signal transmission level to the ambient noise level in the closed loop is the pseudo white signal with respect to the ambient noise level before the pseudo white signal is transmitted to the closed loop. A loudspeaker , wherein a transmission level of a pseudo white signal is adjusted to be a predetermined value or more with respect to the ratio of the transmission levels . A microphone that outputs the collected sound as an audio signal on the transmitting side, a first amplifying means that amplifies the audio signal from the microphone, a speaker that rings according to the audio signal on the receiving side, and an output to the speaker A second amplifying means for amplifying the audio signal; a loss inserting means for inserting a predetermined amount of loss into at least one of the signal paths on the transmitting side and the receiving side; and variably controlling a loss amount inserted from the loss inserting means. Insertion that estimates the gain margin in the closed loop formed through the microphone and the speaker and adjusts the loss amount based on the estimation result via the control means according to the control means and the response signal to the pseudo white signal sent to the signal path Loss amount adjusting means, and the insertion loss amount adjusting means includes a pseudo white signal generator for inserting a pseudo white signal having a finite period in the signal path, and an audio signal. An adder that adds a pseudo white signal, and a cross correlation value of the response signal output from the adder when the pseudo white signal and the pseudo white signal are added to the signal path, and based on the obtained cross correlation value A cross-correlation operation unit that estimates the impulse response of the closed loop, an envelope detector that detects an envelope of the impulse response signal of the closed loop estimated by the cross-correlation operation unit, and a closed loop based on the output signal of the envelope detector A closed loop gain margin estimating unit for estimating a gain margin, a synchronous control unit for performing timing control for sending a pseudo white signal to a signal path from a pseudo white signal generator to a signal path at a predetermined time interval, and an envelope detector The closed-loop impulse response signal estimated by the cross-correlation calculation unit in response to timing information from the synchronization control unit A synchronous addition averaging unit that performs periodic addition averaging processing, an ambient noise extraction unit that extracts an ambient noise signal from a signal transmitted during the closed loop, and an ambient noise level that exists in the closed loop is estimated from the extracted ambient noise signal The noise level estimation unit, the transmission level adjustment unit for adjusting the transmission level of the pseudo white signal based on the estimation result by the noise level estimation unit, and the number of synchronization additions in the synchronization addition averaging unit based on the estimation result by the noise level estimation unit And a sending level adjusting unit that sends the sample signal to the ambient noise level before the sample signal is sent to the closed loop, with the ratio of the sample signal sending level to the ambient noise level in the closed loop being adjusted. It is made by adjusting the transmission level of the sample signal so that the ratio of the levels becomes a predetermined value or more. Based on the statistical properties of the ambient noise level and the number of synchronization additions that have been quantitatively examined in advance, the delay time associated with the synchronization addition average is minimized with respect to the ambient noise level estimated by the noise level estimation unit. A loudspeaker having a minimum number of synchronous additions necessary for the purpose .

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