JP2007243739A - Noise-canceling headphone and method for changing over control for noise cancellation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise-canceling headphone capable of effectively reducing noises and a foreign sound in response to the magnitudes of the sounds of noises and a music and method for changing over a control for a noise cancellation. <P>SOLUTION: The noise-canceling headphone has a noise-canceling feedback control circuit and a gain setting means 9 capable of setting an open-loop gain to a first gain capable of suppressing the magnitude of noises at a value smaller than a fixed value and a second gain capable of suppressing the magnitude of the foreign sound at the value smaller than the fixed value. When both the magnitude of peripheral noises and the magnitude of a sound volume are made smaller than the fixed values, the gain setting means sets the open-loop gain to the second gain. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a noise-canceling headphone and a noise-canceling control switching method, and more particularly, a noise-canceling headphone and a noise-canceling control capable of listening to high-quality music by switching a noise-canceling control mode according to ambient noise conditions. The switching method.

  In recent years, noise canceling headphones capable of canceling ambient noise and listening to music have been commercialized by various companies. These noise-canceling headphones are designed to reduce noise by inputting ambient noise from a microphone and canceling noise output from the speaker in the opposite phase. JP-A-6-343195 (Patent Document 1) and the like can be cited as a related art relating to noise-canceling headphones.

  FIG. 11 shows a simplified control circuit configuration of a headphone that realizes noise cancellation by feedback control.

  In FIG. 11, reference numeral 21 denotes a noise canceling headphone control circuit unit. Reference numeral 2 denotes a sound reproduction unit (hereinafter referred to as a headphone) of a noise canceling headphone. Reference numeral 3 denotes an audio signal reproducing apparatus that outputs an audio signal such as music. In FIG. 11, a silicon player (a portable audio apparatus in which a storage medium for storing music data is a semiconductor memory) is used. The control circuit unit 21 and the headphones 2 may be configured integrally or may be configured separately. In addition to the headphone type, the headphone 2 may be an earphone type.

  The audio signal input from the audio signal reproducing device 3 is subjected to audio signal processing by the control circuit unit 21 and output to the headphones 2 to be reproduced as audio. In the following description, it is described as sound including sound and sound.

  The control circuit unit 21 includes a correction circuit 4, a signal addition unit 5, a filter 6, a headphone amplifier 7, a microphone amplifier 8, and the like. The headphone 2 includes a speaker 13, a microphone 14, a headphone housing 15, a band 16, and the like. Reference numeral 17 is a simplified illustration of the user's ear.

  The output unit of the audio signal reproduction device 3 is connected to the input unit of the correction circuit 4. The output unit of the correction circuit 4 is connected to the positive input unit of the signal adding unit 5. The output unit of the signal adding unit 5 is connected to the input unit of the filter 6. The output part of the filter 6 is connected to the input part of the headphone amplifier 7. The output section of the headphone amplifier 7 is connected to the speaker 13. The speaker 13 and the microphone 14 are attached in close proximity to the headphone housing 15. When the user wears the headphones 2, the microphone 14 collects both sound from the speaker 13 and ambient noise that reaches the microphone 14 via the headphone housing 15.

  The correction circuit 4 corrects the audio signal input from the audio signal reproduction device 3 so that the frequency characteristic in the audible frequency range of the audio output from the speaker 13 is substantially flat. It is. The signal adder 5 is a subtractor that takes the difference between the audio signal from the correction circuit 4 input to the positive input unit and the feedback signal from the microphone amplifier 8 input to the negative input unit. Yes. The filter 6 is a band-pass filter having a large gain in a frequency band where noise is desired to be reduced. The headphone amplifier 7 amplifies the input signal and supplies it to the speaker 13. The microphone 14 collects sound and noise output from the speaker 13, converts them into electric signals, and supplies them to the microphone amplifier 8. The microphone amplifier 8 amplifies the signal from the microphone 14 and feeds it back as a feedback signal to the negative input section of the signal adding section 5.

As described above, the sound reproduction system including the control circuit unit 21, the headphone 2, and the sound signal reproduction device 3 has a negative feedback by the signal addition unit 5, the filter 6, the headphone amplifier 7, the speaker 13, the microphone 14, and the microphone amplifier 8. Configure a loop. Noise is canceled by this negative feedback feedback loop.
JP-A-6-343195

  Noise cancellation headphones with the above feedback control have the feature that the noise reduction effect can be increased by increasing the open loop gain of the noise cancellation feedback control circuit. On the other hand, if the open loop gain is increased, the noise caused by the feedback control is reduced. There is a problem that occurs.

  FIG. 12 shows how the open loop gain characteristic and the open loop phase characteristic are related to the noise when the noise cancellation feedback loop characteristic is expressed by a Bode diagram.

  In FIG. 12, (a) shows the open loop gain characteristic of the noise cancellation feedback loop, and shows two characteristic examples of a large open loop gain and a small open loop gain. (B) is a phase characteristic and shows a phase margin for the two characteristic examples of (a). (C) shows the input / output (O / I) gain characteristics of the control circuit unit 21. In the vicinity of the cut-off frequency of the open loop gain characteristic, the gain increases, indicating that abnormal noise is generated even when there is no music signal. Further, it is shown that when the open loop gain is increased, the phase margin is reduced and the abnormal noise is increased.

  The abnormal noise caused by this feedback control is not noticeable when the surrounding noise is high in an environment such as a busy area in the city, but it is not noticeable when the surrounding noise is low such as a quiet room. There is a tendency to become. In particular, when you try to listen to quiet music by lowering the volume in an environment where the surrounding noise is low, this unusual noise can be heard as an annoying sound. This is due to the characteristic that a relatively loud sound can be heard well.

  However, the conventional noise-canceling headphones increase the loop gain of feedback control in order to cancel the noise regardless of the level of noise or music. For this reason, when listening to music in an environment where the surrounding noise is low, such as in a quiet room, there is a problem that this abnormal sound can be heard as an annoying sound.

  In view of the above problems, an object of the present invention is to provide a noise-canceling headphone that can effectively reduce noise and abnormal noise according to the level of noise and music.

The noise-canceling headphone of the present invention is a noise-canceling headphone that can input a voice signal and hear a voice in which ambient noise has been canceled. A noise-canceling feedback control circuit for canceling ambient noise and the noise-canceling headphone The magnitude of the noise generated due to the first gain that can suppress the noise level of the feedback control circuit to be smaller than a predetermined value and the gain characteristics near the cutoff frequency of the noise cancellation feedback control circuit. Gain setting means that can be set in two ways of a second gain that can be suppressed to be smaller than a predetermined value, and the gain setting means is configured such that when the ambient noise level and the audio volume level are both smaller than the predetermined value. Setting the open loop gain to the second gain; And butterflies.
In the noise-canceling headphone according to the present invention, when the ambient noise level is larger than a predetermined value and the audio volume level is smaller than a predetermined value, the gain setting means sets the open loop gain to the first gain. It is characterized by setting to.
In the noise-canceling headphone according to the present invention, when the magnitude of the ambient noise is larger than a predetermined value and the volume of the voice volume is larger than a predetermined value, the gain setting means sets the open loop gain to the second gain. And a mode switching means for setting to a first gain when the ambient noise level is smaller than a predetermined value and the voice volume is larger than a predetermined value. To do.
In the noise-canceling headphone according to the present invention, when the magnitude of the ambient noise is larger than a predetermined value and the volume of the voice volume is larger than a predetermined value, the gain setting means sets the open loop gain to the first gain. And a mode switching means for setting the second gain when the ambient noise level is smaller than a predetermined value and the voice volume is larger than a predetermined value.
The noise-canceling headphone according to the present invention is characterized in that the gain setting means sets the open loop gain to the first gain when the volume of the sound volume is larger than a predetermined value.
The noise-canceling headphone according to the present invention is characterized in that the gain setting means sets the open loop gain to the second gain when the volume of the sound volume is larger than a predetermined value.
The noise-canceling headphone of the present invention is characterized by comprising storage means for storing the first gain setting data and the second gain setting data.
The noise-canceling headphone according to the present invention is characterized in that the volume of the sound volume is detected by volume position detecting means for detecting a set position of the sound volume.
The noise-canceling headphone of the present invention is characterized in that the ambient noise level is detected by a microphone.
The noise-canceling headphone of the present invention includes a correction circuit that corrects a frequency characteristic in an audible frequency range of sound output from a speaker when the open loop gain is set to a substantially flat characteristic. To do.
The noise cancellation headphone noise canceling control switching method of the present invention is a noise canceling headphone noise canceling control switching method in which an audio signal can be input to listen to the sound whose surrounding noise has been canceled. Is set smaller than a predetermined value, the open loop gain of the noise cancellation feedback control circuit is set to the first gain, and the magnitude of the abnormal noise generated due to the gain characteristics near the cutoff frequency of the noise cancellation feedback control circuit is set. The second gain is set when the height is controlled to be smaller than a predetermined value, and the open loop gain is set to the second gain when the ambient noise level and the sound volume are both smaller than the predetermined value. It is characterized by.
In the noise canceling headphone noise canceling control switching method according to the present invention, the open loop gain is set to the first gain when the ambient noise level is larger than a predetermined value and the sound volume is larger than a predetermined value. It is characterized by setting to.
In the noise canceling headphone noise canceling control switching method according to the present invention, the open loop gain is set to the second gain when the ambient noise level is larger than a predetermined value and the sound volume is larger than a predetermined value. And the first gain is set when the volume of the surrounding noise is smaller than a predetermined value and the volume of the sound volume is larger than a predetermined value.
The noise canceling headphone noise canceling control switching method of the present invention may be configured such that the open loop gain is set to the first gain when the ambient noise level is greater than a predetermined value and the audio volume level is greater than a predetermined value. And the second gain is set when the size of the ambient noise is smaller than a predetermined value and the volume of the sound volume is larger than a predetermined value.
In the noise canceling headphone noise canceling control switching method according to the present invention, the gain setting means sets the open loop gain to the first gain when the volume of the sound volume is larger than a predetermined value. And
In the noise canceling headphone noise canceling control switching method of the present invention, the gain setting means sets the open loop gain to the second gain when the volume of the sound volume is larger than a predetermined value. And
The noise canceling headphone noise canceling control switching method of the present invention is characterized in that the first gain setting data and the second gain setting data are stored.
The noise canceling headphone noise canceling control switching method of the present invention is characterized in that the volume of the sound volume is detected by volume position detecting means for detecting the position of the sound volume.
The noise cancellation headphones noise cancellation control switching method of the present invention is characterized in that ambient noise is detected by a microphone.
In addition, the noise canceling headphone noise canceling control switching method of the present invention corrects so that the frequency characteristic in the audible frequency range of the sound output from the speaker becomes a substantially flat characteristic when the open loop gain is set. It is characterized by doing.

  According to the present invention, it is possible to provide a noise-canceling headphone that can effectively reduce noise and abnormal noise according to the level of noise or music.

  The best mode for carrying out the present invention will be specifically described below with reference to the drawings.

(First embodiment)
FIG. 1 shows a first embodiment of a control circuit configuration of a noise canceling headphone according to the present invention.

  First, the control circuit configuration of the noise canceling headphone will be described.

  In FIG. 1, reference numeral 1 denotes a control circuit unit of a noise canceling headphone. Reference numeral 2 denotes a sound reproduction unit (hereinafter referred to as a headphone) of a noise canceling headphone. Reference numeral 3 denotes an audio signal reproducing apparatus that outputs an audio signal such as music. In FIG. 1, the apparatus is a silicon player (a portable audio apparatus in which a storage medium for storing music data is a semiconductor memory). The control circuit unit 1 and the headphones 2 can be configured as a single body or as separate bodies. Further, the headphone 2 can be an earphone type in addition to the headphone type.

  The audio signal input from the audio signal reproduction device 3 to the control circuit unit 1 is subjected to audio signal processing by the control circuit unit 1 and output to the headphones 2 to be reproduced as audio.

  The control circuit unit 1 includes a correction circuit 24, a signal addition unit 5, a filter 26, a headphone amplifier 7, a microphone amplifier 8, a gain adjustment unit 9, a gain table 10, a volume position detection unit 11, a mode change switch 12, and the like. Yes. The headphone 2 includes a speaker 13, a microphone 14, a headphone housing 15, a band 16, and the like. Reference numeral 17 is a simplified illustration of the user's ear.

  The output unit of the audio signal reproduction device 3 is connected to the input unit of the correction circuit 24. The output unit of the correction circuit 24 is connected to the positive input unit of the signal adding unit 5. The output unit of the signal adding unit 5 is connected to the input unit of the filter 26, and the output unit of the filter 26 is connected to the input unit of the headphone amplifier 7. The output section of the headphone amplifier 7 is connected to the input section of the speaker 13. The speaker 13 and the microphone 14 are attached in close proximity to the headphone housing 15. When the user wears the headphones 2, the microphone 14 collects both sound from the speaker 13 and ambient noise that reaches the microphone 14 via the headphone housing 15. In addition, the microphone 14 collects sound and noise output from the speaker 13, converts them into electric signals, and supplies them to the microphone amplifier 8. The microphone amplifier 8 amplifies the signal from the microphone 14 and feeds it back to the negative input unit of the signal adding unit 5 as a feedback signal.

  The correction circuit 24 corrects the audio signal input from the audio signal reproduction device 3 so that the frequency characteristic in the audible frequency range of the audio output from the speaker 13 is substantially flat. It is. The signal adder 5 is a subtractor that takes the difference between the audio signal from the correction circuit 4 input to the positive input unit and the feedback signal from the microphone amplifier 8 input to the negative input unit. . The filter 26 is a band-pass filter having a large gain in a frequency band where noise is desired to be reduced.

  The gain adjustment unit 9 sets the gains of the filter 26 and the correction circuit 24 according to the control mode of the noise cancellation control. The gain table 10 stores gain data set at this time. There are two types of data stored in the gain table 10 as will be apparent from the following description. The first data has a sufficiently large value for the open loop gain of the noise cancellation feedback to cancel the noise. Is. When the first data is set, the abnormal noise cannot be sufficiently suppressed, but it is not a concern if the noise level is a predetermined value or more. The second data is set to a small value in order to suppress abnormal noise. When the second data is set, noise cannot be sufficiently suppressed. It will be suppressed to the extent that you do not care. These first and second data are determined and stored in advance through experiments or the like. In the following description, when the first data is set, “open loop gain is set large”, and when the second data is set, “open loop gain is set small”.

  The volume position detection unit 11 detects a volume setting position for adjusting the volume of the reproduced sound and outputs the detected position to the gain adjustment unit 9. The mode switch 12 is used by the user to switch the control mode of the noise cancellation control according to the surrounding noise situation. When the mode selector switch 12 is switched, the output signal is switched from the high level to the low level, or from the low level to the high level. Thereby, the gain adjustment part 9 can detect which mode is switched to.

  In this way, the audio reproduction system including the control circuit unit 1, the headphones 2, and the audio signal reproduction device 3 constitutes a negative feedback feedback loop by the signal addition unit 5, the filter 26, the speaker 13, the microphone 14, and the microphone amplifier 8. In addition, the gain of the filter 26 and the gain of the correction circuit 24 can be switched according to the surrounding noise conditions.

  FIG. 2 shows how the open loop gain of the noise cancellation feedback loop in the present embodiment is set depending on the noise and the volume.

  As shown in FIG. 2, the noise cancellation control mode that is operated when noise is high is mode [1], and the noise cancellation control mode that is operated when noise is low is mode [2]. In mode [1] when the noise is high, the open loop gain is set small when the volume is set large, and the open loop gain is set large when the volume is set small. In mode [2] when the noise is low, when the volume is set large, the open loop gain is set large, and when the volume is set small, the open loop gain is set small.

  FIG. 3 shows an operation flow of the present embodiment.

  First, noise is detected in step S1. This corresponds to the user listening to ambient noise. Next, in step S2, it is determined whether or not the noise is loud. If the user determines that the noise is loud, the process proceeds to step S3 and the mode [1] is set. This is performed by the user operating the mode switch 12 to the mode [1] side.

  Next, in step S5, the gain setting unit 9 checks whether the volume is large. This is determined by looking at the output state of the volume position detector 11 and determining whether the volume position is larger than a predetermined position. If it is determined that the volume is large, the process proceeds to step S6, where the open loop gain is set small. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. The open loop gain is adjusted by the gain of the filter 26. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In step S5, when the gain setting unit 9 determines that the volume is small, the process proceeds to step S7, where the open loop gain is set large. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. The open loop gain is adjusted by the gain of the filter 26. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  If the user determines that the noise is low in step S2, the process proceeds to step S4 and the mode [2] is set. This is performed by the user operating the mode switch 12 to the mode [2] side.

  Next, in step S8, it is checked whether or not the volume is small. The gain setting unit 9 checks the output state of the volume position detection unit 11 and determines whether the volume position is smaller than a predetermined position. If the gain setting unit 9 determines that the volume is small, the process proceeds to step S9, where the open loop gain is set large. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. The open loop gain is adjusted by the gain of the filter 26. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In step S8, when the gain setting unit 9 determines that the volume is large, the process proceeds to step S10, where the open loop gain is set small. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. The open loop gain is adjusted by the gain of the filter 26. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  As described above, the noise-canceling headphone according to the present embodiment operates, so that the open-loop gain is set to be small when the noise is small and the volume is small. Therefore, it is possible to suppress the abnormal noise to be small in a state where the noise anxious about the abnormal noise is small. Further, according to the present embodiment, it is possible to realize the control mode switching by switching the mode switch according to the level of noise. Also, when the noise is loud and the volume is large, the open loop gain can be reduced to make the feedback control loop more stable.

  In the embodiment described above, in the step indicated by the dotted frame A in FIG. 3, the user determines the level of noise, and the mode changeover switch 12 is operated and switched by the user.

  On the other hand, noise can be detected by a microphone, and the steps shown in the dotted frame A in FIG. 3 can be automatically executed.

  FIG. 4 shows a modified example at this time. In this modification, a microphone 18 and a microphone amplifier 19 are provided in place of the mode switch 12. The microphone 18 is attached toward the outside of the headphone housing 15 so that ambient noise can be detected. The microphone amplifier 19 amplifies the signal from the microphone 18 and outputs the amplified signal to the gain setting unit 29.

  The operation of this modification will be described with respect to part A of the flowchart of FIG.

  In step S1, noise is detected. This is performed by the gain setting unit 9 taking in the output of the microphone amplifier 19. The microphone amplifier 19 in this case may be a comparator that compares whether the value is larger or smaller than a predetermined value and outputs the result.

  Next, it progresses to step S2 and it is checked whether noise is loud. At this time, the gain setting unit 29 determines the level of noise by checking whether the output of the microphone amplifier 19 is larger or smaller than a predetermined value.

  In step S2, the gain setting unit 29 proceeds to step S3 and sets the mode [1] when determining that the noise is loud. If it is determined that the noise level is low, the process proceeds to step S3, where mode [2] is set.

  Even in this modified example, since the open loop gain is set to be small when the noise is small and the volume is small, the abnormal noise can be suppressed to be small when the noise at which the abnormal noise is concerned is small. In addition, the control mode can be switched by switching the mode switch according to the level of noise. Also, when the noise is loud and the volume is large, the open loop gain can be reduced to make the feedback control loop more stable. Furthermore, in this modification, since the noise is detected by the microphone 18 and the mode is switched, the mode can be automatically switched without bothering the user.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The control circuit configuration is the same as in FIG. 1 or FIG. 4, but the operations of the gain setting units 9 and 29 are different. Therefore, what corresponds to the gain setting unit 9 will be described below as the gain setting unit 39, and what corresponds to the gain setting unit 29 will be described as the gain setting unit 49. The mode changeover switch 12 can be the same as that of the first embodiment by replacing mode [3] described below with mode [1] and mode [4] with mode [2].

  FIG. 5 shows how the open loop gain of the noise cancellation feedback loop in the present embodiment is set depending on the noise and the volume.

  As shown in FIG. 5, the noise cancellation control mode that is operated when noise is high is mode [3], and the noise cancellation control mode that is operated when noise is low is mode [4]. In mode [3] when the noise level is high, the open loop gain is set large. In mode [4] when the noise is low, the open loop gain is set small.

  FIG. 6 shows an operation flow of the present embodiment.

  First, a case where the present embodiment is applied to the control circuit configuration shown in FIG. 1 will be described.

In step S11, noise is detected by the user.
Next, in step S12, the user determines whether the noise is loud. If it is determined that the noise is loud, the process proceeds to step S13, and the mode switch 12 is set to mode [3]. This is performed by the user operating the mode switch 12 to the mode [3] side. At this time, the mode switch 12 outputs a signal level output corresponding to the mode [3] to the gain setting unit 39. Accordingly, the gain setting unit 39 sets the gain of the filter 26 to be large in order to increase the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  If it is determined in step S12 that the noise is low, the process proceeds to step S14, and the mode switch 12 is set to mode [4]. This is performed by the user operating the mode switch 12 to the mode [4] side. At this time, the mode switch 12 outputs a signal level output corresponding to the mode [4] to the gain setting unit 39. Accordingly, the gain setting unit 39 sets the gain of the filter 26 to be small in order to reduce the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. As the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  As described above, the noise-canceling headphone according to the present embodiment operates, so that the open loop gain is set large when the noise is high, and the open loop gain is set small when the noise is low. Therefore, it is possible to suppress the abnormal noise small when the noise anxious about the noise is small, and to suppress the noise small when the noise anxious about the noise is large. In addition, according to the present embodiment, this state can be realized by switching the mode switch according to the level of noise. When the noise is low, the open loop gain can be reduced to make the feedback control loop more stable.

  Next, a modification in which the present embodiment is applied to the control circuit configuration shown in FIG. 4 will be described.

  In step S11, noise is detected. This is performed by the gain setting unit 49 taking in the output of the microphone amplifier 19. The microphone amplifier 19 in this case may be a comparator that compares whether the value is larger or smaller than a predetermined value and outputs the result.

  Next, it progresses to step S12 and it is checked whether noise is loud. At this time, the gain setting unit 49 determines the level of noise by checking whether the output of the microphone amplifier 19 is larger or smaller than a predetermined value.

  In step S12, the gain setting unit 49 proceeds to step S13 and sets the mode [3] when determining that the noise is loud. When the mode [3] is set, the gain setting unit 49 sets the gain of the filter 26 to be large in order to increase the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In step S12, when the setting unit 49 determines that the noise is low, the setting unit 49 proceeds to step S14 and sets the mode [4]. The gain setting unit 49 sets the gain of the filter 26 to be small in order to reduce the open loop gain by setting the mode [4]. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  Even in this modified example, the open loop gain is set to be small when the noise is low, and the open loop gain is set to be low when the noise is high. In addition, the noise can be reduced to a small level in a state where the noise is a concern. In addition, according to the present embodiment, this state can be realized by switching the mode switch according to the level of noise. When the noise is low, the open loop gain can be reduced to make the feedback control loop more stable. Furthermore, in this modification, since the noise is detected by the microphone 18 and the mode is switched, the mode can be automatically switched without bothering the user.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.
The control circuit configuration is the same as that in FIG. 4, but the operation of the gain setting unit 29 is different. Therefore, what corresponds to the gain setting unit 29 will be described below as the gain setting unit 59.

  FIG. 7 shows how the open loop gain of the noise cancellation feedback loop in the present embodiment is set depending on the noise and the volume.

  In this embodiment, as shown in FIG. 7, the open loop gain is set small when the noise is low and the volume is set low, and the open loop gain is set high otherwise.

  FIG. 8 shows an operation flow of the present embodiment.

  In step S21 of FIG. 8, noise is detected. This is performed by the gain setting unit 59 taking in the output of the microphone amplifier 19. The microphone amplifier 19 in this case may be a comparator that compares whether the value is larger or smaller than a predetermined value and outputs the result.

  Next, it progresses to step S22 and it is checked whether noise is loud. At this time, the gain setting unit 59 determines the level of noise by checking whether the output of the microphone amplifier 19 is larger or smaller than a predetermined value.

  In step S22, the gain setting unit 59 proceeds to step S25 when determining that the noise is loud, and sets the gain of the filter 26 to be large in order to increase the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so that the frequency characteristic of the audio output is flattened.

  In step S22, when the gain setting unit 59 determines that the noise is low, the process proceeds to step S23 to check whether the volume is low. At this time, the gain setting unit 59 determines the size of the volume from the position of the volume by looking at the output of the volume position detection unit 11.

  When it is determined in step S23 that the volume is small, the process proceeds to step S24, and the gain of the filter 26 is set small to reduce the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  If it is determined in step S23 that the volume is large, the process proceeds to step S25, and the gain of the filter 26 is set large in order to increase the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In the present embodiment, when the noise is low and the volume is set low, the open loop gain is set low, so that the abnormal noise can be suppressed to a low level in a state where the noise that is anxious is low. When other abnormal noise is not a concern, the open loop gain is set to be large and noise is reduced. Furthermore, in this embodiment, since the noise is detected by the microphone 18 and the position of the volume is automatically detected to switch the control mode, it is possible to switch automatically without bothering the user.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
The control circuit configuration is the same as that in FIG. 4, but the operation of the gain setting unit 29 is different. Therefore, what corresponds to the gain setting unit 29 will be described below as the gain setting unit 69.

  FIG. 9 shows how the open loop gain of the noise cancellation feedback loop in the present embodiment is set depending on the noise and the volume.

  In this embodiment, as shown in FIG. 9, the open loop gain is set large when the noise is high and the volume is set small, and the open loop gain is set small otherwise.

  FIG. 10 shows an operation flow of the present embodiment.

  In step S31 of FIG. 10, noise is detected. This is performed by the gain setting unit 69 taking in the output of the microphone amplifier 19. The microphone amplifier 19 in this case may be a comparator that compares whether the value is larger or smaller than a predetermined value and outputs the result.

  Next, it progresses to step S32 and it is checked whether noise is loud. At this time, the gain setting unit 69 determines the level of noise by checking whether the output of the microphone amplifier 19 is larger or smaller than a predetermined value.

  In step S32, the gain setting unit 69 proceeds to step S35 when determining that the noise is low, and sets the gain of the filter 26 to be small in order to reduce the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In step S32, the gain setting unit 69 proceeds to step S33 when determining that the noise is loud, and checks whether the volume is small. At this time, the gain setting unit 69 determines the size of the volume from the position of the volume by looking at the output of the volume position detection unit 11.

  When it is determined in step S33 that the volume is small, the process proceeds to step S34, and the gain of the filter 26 is set large in order to increase the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the first data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  If it is determined in step S33 that the volume is large, the process proceeds to step S35, and the gain of the filter 26 is set small in order to reduce the open loop gain. Since the gain data to be set is stored in advance in the storage means 10 as a gain table, the second data can be read and set from this. Further, as the gain of the filter 26 is adjusted, the gain of the correction circuit 24 is set so as to flatten the frequency characteristic of the audio output.

  In the present embodiment, since the open loop gain is set to be large when the noise is large and the volume is small, the noise can be suppressed to a small level in a state where the noise is anxious, and other noises are not anxious. In this state, the open loop gain is set small, so that the control loop can be stabilized. In addition, when the noise is low and the volume is low, the open loop gain is set small, so that no abnormal noise can be heard. Furthermore, in this embodiment, since the noise is detected by the microphone 18 and the position of the volume is automatically detected to switch the control mode, it is possible to switch automatically without bothering the user.

  The first to fourth embodiments have been specifically described above, but these embodiments are common in that the open loop gain is set to be large when the noise is large and the volume is small. It is also common that the open loop gain is set small when the noise is low and the volume is small.

  Further, although the filter 26 has a band pass characteristic, it can be a low pass characteristic or a high pass characteristic in consideration of other elements constituting the feedback loop. The configuration of the feedback loop is not limited to the configuration of the above embodiment. For example, a configuration in which the filter 26 is inserted between the microphone amplifier 8 and the signal adding unit 5 may be employed.

  As mentioned above, although this invention was demonstrated by specific embodiment, it cannot be overemphasized that this invention is not limited to the said embodiment, It can change and implement in the range which does not deviate from the summary of this invention.

  The present invention is not limited to noise-canceling headphones, and can be widely used for devices that attempt to suppress noise.

It is a control circuit block diagram which shows embodiment of the noise cancellation headphones by this invention. It is a figure explaining the control mode of 1st Embodiment by this invention. It is an operation | movement flowchart of the noise cancellation headphones of 1st Embodiment by this invention. It is a control circuit block diagram which shows embodiment of the noise cancellation headphones by this invention. It is a figure explaining the control mode of 2nd Embodiment by this invention. It is an operation | movement flowchart of the noise cancellation headphones of 2nd Embodiment by this invention. It is a figure explaining the control mode of 3rd Embodiment by this invention. It is an operation | movement flowchart of the noise cancellation headphones of 3rd Embodiment by this invention. It is a figure explaining the control mode of 4th Embodiment by this invention. It is an operation | movement flowchart of the noise cancellation headphones of 4th Embodiment by this invention. It is a figure which shows the control circuit structural example of the noise cancellation headphones of a prior art. It is a figure explaining abnormal noise generation | occurrence | production of the noise cancellation headphones of a prior art.

Explanation of symbols

1, 21 ... Control circuit part 2 ... Headphone (sound reproduction part)
3 ... Silicone player (audio signal playback device)
4, 24 ... Correction circuit 5 ... Signal addition unit 6, 26 ... Filter 7 ... Headphone amplifier 8, 19 ... Microphone amplifier 9 ... Gain setting unit 10 ... Gain table 11 ... Volume position detector 12 ... Mode switch 13 ... Speaker 14 ... Microphone 15 ... Headphone housing 16 ... Band 17 ... Ear

Claims (20)

In the noise canceling headphones that can input the audio signal and hear the sound in which the surrounding noise is canceled,
A noise cancellation feedback control circuit for canceling ambient noise,
The open loop gain of the noise cancellation feedback control circuit is an abnormal noise generated due to the first gain capable of suppressing the noise level to be smaller than a predetermined value and the gain characteristics near the cutoff frequency of the noise cancellation feedback control circuit. Gain setting means that can be set in two ways of a second gain that can be controlled to be smaller than a predetermined value,
The noise-canceling headphone, wherein the gain setting means sets the open-loop gain to the second gain when the ambient noise level and the audio volume level are both smaller than a predetermined value.   The gain setting means sets the open loop gain to the first gain when the magnitude of the ambient noise is larger than a predetermined value and the volume of the voice volume is smaller than a predetermined value. The noise-canceling headphones according to 1.   The gain setting means sets the open loop gain to the second gain when the ambient noise level is greater than a predetermined value and the audio volume level is greater than a predetermined value, and the ambient noise level is increased. The noise-canceling headphone according to claim 2, further comprising mode switching means for setting the first gain when the voice volume is smaller than a predetermined value and the voice volume is larger than the predetermined value.   The gain setting means sets the open loop gain to the first gain when the ambient noise level is greater than a predetermined value and the audio volume level is greater than a predetermined value, and the ambient noise level is set. The noise canceling headphone according to claim 2, further comprising mode switching means for setting the second gain when the sound volume is smaller than a predetermined value and the sound volume is larger than the predetermined value.   The noise canceling headphone according to claim 2, wherein the gain setting means sets the open loop gain to the first gain when the volume of the sound volume is larger than a predetermined value.   The noise canceling headphone according to claim 2, wherein the gain setting means sets the open loop gain to the second gain when the volume of the sound volume is larger than a predetermined value.   The noise canceling headphone according to any one of claims 1 to 6, further comprising storage means for storing the first gain setting data and the second gain setting data.   8. The noise-canceling headphone according to claim 1, wherein the volume of the sound volume is detected by a volume position detecting unit that detects a set position of the sound volume.   The noise-canceling headphone according to any one of claims 1 to 8, wherein a magnitude of the ambient noise is detected by a microphone.   The correction circuit which corrects the frequency characteristic in the audible frequency range of the sound output from the speaker when the open loop gain is set to a substantially flat characteristic. Noise-canceling headphones according to item 1. In the noise canceling headphone noise canceling control switching method, the sound signal can be heard by inputting an audio signal and the surrounding noise is canceled.
When the noise level is controlled to be smaller than a predetermined value, the open loop gain of the noise cancellation feedback control circuit is set to the first gain,
When the noise cancellation feedback control circuit has a gain characteristic that is less than a predetermined value, the second gain is set to suppress the noise generated due to the gain characteristics near the cutoff frequency.
A noise cancellation control switching method for a noise cancellation headphone, wherein the open loop gain is set to the second gain when the ambient noise level and the audio volume level are both smaller than a predetermined value.   12. The noise cancellation according to claim 11, wherein the open loop gain is set to the first gain when the magnitude of the ambient noise is larger than a predetermined value and the volume of the voice volume is larger than a predetermined value. Headphone noise cancellation control switching method. When the magnitude of the ambient noise is greater than a predetermined value and the volume of the audio volume is greater than a predetermined value, the open loop gain is set to the second gain;
The noise cancellation control of the noise canceling headphone according to claim 12, wherein the first gain is set when the ambient noise level is smaller than a predetermined value and the volume of the sound volume is larger than a predetermined value. Switching method. When the magnitude of the ambient noise is greater than a predetermined value and the volume of the audio volume is greater than a predetermined value, the open loop gain is set to the first gain;
13. The noise cancellation control of the noise canceling headphones according to claim 12, wherein the second gain is set when the ambient noise level is smaller than a predetermined value and the sound volume is larger than a predetermined value. Switching method.   The noise cancellation control switching of the noise cancellation headphones according to claim 12, wherein the gain setting means sets the open loop gain to the first gain when the volume of the audio volume is larger than a predetermined value. Method.   The noise canceling control switching of the noise canceling headphone according to claim 12, wherein the gain setting means sets the open loop gain to the second gain when the volume of the sound volume is larger than a predetermined value. Method.   The noise cancellation control switching method for the noise cancellation headphones according to any one of claims 11 to 16, wherein the first gain setting data and the second gain setting data are stored.   The noise cancellation control switching of the noise cancellation headphones according to any one of claims 11 to 17, wherein the volume of the audio volume is detected by volume position detection means for detecting the position of the audio volume. Method.   The noise cancellation control switching method of the noise cancellation headphones according to any one of claims 11 to 18, wherein ambient noise is detected by a microphone.   20. The correction according to any one of claims 11 to 19, wherein when the open loop gain is set, the frequency characteristic in the audible frequency range of the sound output from the speaker is corrected to be a substantially flat characteristic. The noise cancellation headphone noise cancellation control switching method according to one item.

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