JP5408546B2 - Volume limiter and sound collector - Google Patents

Description

  The present invention relates to a volume restriction device that suppresses sudden sound that occurs when a loud sound is instantaneously input, and a sound collector that includes the sound volume restriction device.

  A sound collector such as a hearing aid collects ambient external sound and transmits it to a user or the like via an earphone or the like, and is used especially to compensate for hearing that has been aggravated by the elderly and the like. Such a sound collector amplifies sudden and loud external sound such as an impact sound generated when a car whistle or an object collides, and outputs the amplified sound from the earphone. The shock of the user that is felt when these sudden sounds are suddenly output from the earphones is extraordinary and is reminiscent of the use of a sound collector.

  For this reason, the sound collector is incorporated with a volume limiter such as an output limiter circuit or an AGC (Automatic Gain Control) circuit so that no sound exceeding a predetermined limit level is output even if a sudden sound is input. There are many. [Patent Document 1] discloses an invention relating to a hearing aid provided with a volume limiting device that suppresses only frequency components in the high sound range.

  However, the restriction levels of these volume restriction devices are basically fixed. In such a conventional volume restriction device with a fixed restriction level, as shown in FIG. 18A, when a sudden sound S is input in a state where the voice level Vh is relatively high in conversational voice and ambient noise. The sudden sound S is attenuated and suppressed to a fixed limit level Vhs and output. In this manner, in the state of the relatively high sound level Vh, the level difference between the restriction level Vhs and the sound level Vh is relatively small, the volume restriction device functions effectively, and the user does not receive much shock. However, as shown in FIG. 18B, even when the sudden sound S is input in a VL state where the surroundings are quiet and the sound level is relatively low, the conventional volume restriction device has a restriction level where the sudden sound S is fixed. It attenuates and suppresses only to Vhs. In such a case, the level difference between the audio level VL and the restriction level Vhs is large, and even if the volume restriction device functions, the user is shocked.

  With regard to this point, the following [Patent Document 2] discloses an invention in which the threshold value for sudden sound determination is changed in accordance with the average amplitude of the input signal within a certain period of time in addition to the volume limiting device in which the upper limit of the limit level is fixed. ing.

Japanese Patent Laid-Open No. 2-058999 JP-A-6-276599

  However, the invention described in [Patent Document 2] has a problem that the input signal is processed as a digital signal and the circuit configuration is complicated and expensive. In addition, because the input signal is delayed for a while, the sudden sound is suppressed, so there is a time lag between the sound from the sound collector and the actual sound, and the sound can be heard twice, or the movement of the conversation partner's mouth There is a problem that the user feels uncomfortable due to deviation from the audible voice.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sound volume limiter and a sound collector that can limit sudden sound according to an external sound level with a simple circuit configuration. And

The present invention
(1) an attenuating unit 30 for attenuating an input audio signal under a predetermined condition;
When the signal output from the attenuating unit 30 is detected and the level of the audio signal is in a first state where the level of the audio signal increases steeply with time, the attenuating unit 30 attenuates the audio signal. 30 so that the attenuation unit 30 does not attenuate the audio signal when in the second state where the level of the audio signal increases more gradually over time than in the first state, or An attenuation control unit 20 for controlling the attenuation unit 30 so that the attenuation amount by which the attenuation unit 30 attenuates the audio signal is smaller than that in the first state ,
Before SL attenuation control unit 20, a detection sensitivity control unit 36 detects the level of the audio signal subjected to the sensitivity control unit 36 is output from the attenuation section 30, the attenuation of the attenuation section 30 in accordance with the level A level detection unit 38 that outputs a control signal for control, and a delay unit 34 that delays the control signal for a predetermined time,
The detection sensitivity control unit 36 attenuates the level of the signal output from the attenuation unit 30 to the level detection unit 38 when the control signal delayed by the delay unit 34 exceeds a first threshold value,
The first state is a state in which the control signal delayed by the delay unit 34 does not exceed the first threshold, and the control signal exceeds a second threshold greater than the first threshold. by providing the features and to Ruoto amount limiter 50a that there, to solve the above problems.
( 2 ) an attenuating unit 30 for attenuating an input audio signal under a predetermined condition;
When the signal output from the attenuating unit 30 is detected and the level of the audio signal is in a first state where the level of the audio signal increases steeply with time, the attenuating unit 30 attenuates the audio signal. 30 so that the attenuation unit 30 does not attenuate the audio signal when in the second state where the level of the audio signal increases more gradually over time than in the first state, or An attenuation control unit 20 for controlling the attenuation unit 30 so that the attenuation amount by which the attenuation unit 30 attenuates the audio signal is smaller than that in the first state,
The attenuation control unit 20 includes a detection sensitivity control unit 36 and a level detection unit 38 that outputs a control signal for controlling the attenuation of the attenuation unit 30 in accordance with the level of the audio signal output from the attenuation unit 30. And a delay unit 34 that delays the control signal that has passed through the detection sensitivity control unit 36 for a predetermined time,
The detection sensitivity control unit 36 attenuates the level of the control signal when the control signal delayed by the delay unit 34 exceeds a first threshold,
The first state is a state in which the control signal delayed by the delay unit 34 does not exceed the first threshold, and the control signal exceeds a second threshold greater than the first threshold. by providing the features and to Ruoto amount limiter 50a that there, to solve the above problems.
( 3 ) an attenuating unit 30 for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit 30 is detected and the level of the audio signal is in a first state where the level of the audio signal increases steeply with time, the attenuating unit 30 attenuates the audio signal. 30 so that the attenuation unit 30 does not attenuate the audio signal when in the second state where the level of the audio signal increases more gradually over time than in the first state, or An attenuation control unit 20 for controlling the attenuation unit 30 so that the attenuation amount by which the attenuation unit 30 attenuates the audio signal is smaller than that in the first state,
The attenuation control unit 20 detects the level of the audio signal output from the delay unit 34, the detection sensitivity control unit 36, and the attenuation unit 30 and passed through the detection sensitivity control unit 36, and the attenuation unit according to the level. A level detection unit 38 that outputs a control signal for controlling the attenuation of 30;
The detection sensitivity control unit 36 attenuates the level of the signal output from the attenuation unit 30 to the level detection unit 38 after the control signal exceeds the first threshold, to the first threshold,
The delay unit 34 delays the attenuation operation of the detection sensitivity control unit 36 so that the detection sensitivity control unit 36 attenuates the signal to the first threshold over a first time,
In the first state, the control signal exceeds a second threshold value that is greater than the first threshold value while the detection sensitivity control unit 36 attenuates the signal level to the first threshold value. by providing the features and to Ruoto amount limiter 50a to be a state, to solve the above problems.
( 4 ) an attenuation unit 30 for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit 30 is detected and the level of the audio signal is in a first state where the level of the audio signal increases steeply with time, the attenuating unit 30 attenuates the audio signal. 30 so that the attenuation unit 30 does not attenuate the audio signal when in the second state where the level of the audio signal increases more gradually over time than in the first state, or An attenuation control unit 20 for controlling the attenuation unit 30 so that the attenuation amount by which the attenuation unit 30 attenuates the audio signal is smaller than that in the first state,
The attenuation control unit 20 includes a detection sensitivity control unit 36,
The level of the audio signal output from the attenuation unit 20 and passed through the detection sensitivity control unit 36 is detected, and a first control signal that is a signal obtained by delaying a signal corresponding to the level for a first time is detected as the detection sensitivity control unit. A first delay unit 34a that outputs to 36,
The second control is a signal obtained by detecting the level of the audio signal output from the attenuation unit 30 and passing through the detection sensitivity control unit 36 and delaying the signal corresponding to the level by a second time shorter than the first time. A second delay unit 34b for outputting a signal to the attenuation unit 30,
The detection sensitivity control unit 36 attenuates the level of the signal output from the attenuation unit 30 to the second delay unit 34b when the first control signal exceeds a first threshold,
The first state is a state in which the second control signal exceeds a second threshold,
When the first control signal exceeds the first threshold, the detection sensitivity control unit 36 prevents the second control signal from exceeding the second threshold from the attenuation unit 30. by providing the features and to Ruoto amount limiting unit 50b that attenuate the level of the signal output to the delay unit 34b, to solve the above problems.
( 5 ) The volume restriction devices 50a and 50b according to any one of (1) to ( 4 ) above, and the attenuation unit 30 of the volume restriction devices 50a and 50b by converting external sound into an electric sound signal. A sound collector 80 comprising: a sound collecting section 42 for inputting to the sound volume; and a sound output section 40 for converting sound signals output from the attenuation section 30 of the volume restriction devices 50a and 50b into sound. By providing, the above-mentioned problems are solved.

  Since the volume restriction device and the sound collector according to the present invention restrict sudden sounds according to the external sound level, it is possible to always reduce the shock to the user due to sudden sounds. In addition, since the circuit configuration is simple, the device itself can be provided at a low cost.

It is a block diagram which shows the volume control apparatus of the 1st form which concerns on this invention. 1 is a circuit diagram showing a volume limiting device according to a first embodiment of the present invention. It is a circuit diagram which shows the modification of the volume control apparatus of the 1st form which concerns on this invention. It is a circuit diagram which shows the modification of the volume control apparatus of the 1st form which concerns on this invention. It is a figure explaining operation | movement of the volume control apparatus of the 1st form which concerns on this invention. It is a figure explaining operation | movement of the volume control apparatus of the 1st form which concerns on this invention. It is a block diagram which shows the volume control apparatus of the 2nd form which concerns on this invention. It is a circuit diagram which shows the volume control apparatus of the 2nd form which concerns on this invention. It is a figure which shows the modification of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure which shows the modification of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure explaining operation | movement of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure which shows the signal waveform of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure explaining operation | movement of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure which shows the signal waveform of the volume control apparatus of the 2nd form which concerns on this invention. It is a figure which shows the sudden sound suppression effect of the volume control apparatus which concerns on this invention. It is a block diagram which shows the sound collector which concerns on this invention. It is a figure explaining the sudden sound suppression effect of the volume control apparatus which concerns on this invention. It is a figure explaining suppression of sudden sound in a prior art.

  DESCRIPTION OF EMBODIMENTS Embodiments of a volume restriction device and a sound collector according to the present invention will be described with reference to the drawings. The volume limiting device 50a according to the first embodiment shown in FIG. 1 includes an input terminal 10 to which an audio signal is input, an attenuation unit 30 that attenuates the input audio signal under a predetermined condition, and an output from the attenuation unit 30. An attenuation control unit 20 that detects a signal to be transmitted and controls the attenuation unit 30 according to the state of the audio signal, and an output terminal 12 that outputs an output signal from the attenuation unit 30 to the audio output unit 40 described later. ing.

  The attenuation control unit 20 detects the level of the audio signal output from the detection sensitivity control unit 36 and the attenuation unit 30 and passed through the detection sensitivity control unit 36, and controls the attenuation of the attenuation unit 30 according to the level. A level detection unit 38 that outputs a signal and a delay unit 34 that delays the control signal for a predetermined time are provided.

  Next, the configuration of the volume restriction device 50a will be described in more detail. FIG. 2 is a circuit diagram showing an embodiment of the volume limiting device 50a. Note that the signal at the point P1 in FIG. 2 is an audio signal output from the attenuation unit 30 and passed through the detection sensitivity control unit 36, and the signal at the point P is a control signal. The signal at the point Q is a control signal delayed by the delay unit 34.

  Further, the detection sensitivity control unit 36 and the level detection unit 38 of the attenuation control unit 20 in FIG. 2 may be provided with a level detection unit 38 before the detection sensitivity control unit 36 as shown in FIG. When the level detection unit 38 is located at the subsequent stage of the detection sensitivity control unit 36, the capacitor element of the level detection unit 38 is charged by this sudden sound signal when an instantaneous sudden sound is input to the sound signal. The electric charge charged in the capacitor element is then discharged according to the release time constant of the level detection unit 38. This discharge time may be several seconds. During this time, the attenuation unit 30 may continue to operate, and the output of the volume control device 50a may be temporarily silent. However, according to the configuration of FIG. 3, since the detection sensitivity control unit 36 and the delay unit 34 are arranged after the level detection unit 38, the detection sensitivity control unit 36 functions and functions as a level detector when discharging from the capacitor element. The output voltage of the part is rapidly reduced. For this reason, the operation time of the attenuating unit 30 is remarkably shortened, and therefore the time of the silent state can be greatly shortened. The position of the buffer amplifier Q3 in the volume limiting device 50a in FIG. 3 may be provided between the detection sensitivity control unit 36 and the delay unit 34, or a variable gain amplification circuit is used for the detection sensitivity control unit. You may make it also serve as a function.

  Further, the volume restriction device 50a may be configured by combining the detection sensitivity control unit 36 and the delay unit 34 as shown in FIG. When the transistor element is used for attenuation control of a large-amplitude AC signal, the distortion increases and the linearity of the control is impaired. However, according to the configuration of FIG. 4, the transistor element Q2 handles only a direct current and performs ideal control. I can do things.

  Next, the operation of the volume restriction device 50a will be described with reference to FIG. 2, FIG. 5, and FIG. In FIGS. 5 and 6, for the convenience of explanation, the influence of amplification by the amplifying unit 14 and the buffer amplifier Q3 is ignored. 5 (a) and 6 (a) show an audio signal input to the input terminal 10, and FIGS. 5 (b) and 6 (b) show a control signal at point P in FIG. 5 (c) and FIG. 6 (c) show output signals at the output end 12. FIG.

  First, the case where the level of the audio signal input to the input terminal 10 gradually increases with time as shown in FIG. 5A will be described. Note that the state in which the level of the audio signal input to the input terminal 10 gradually increases with time is that the delay unit 34 before the control signal (signal at the point P) exceeds the attenuation start level Vb of the attenuation unit 30. It is assumed that the delayed control signal (control signal at point Q) exceeds the sensitivity change start level Va (<Vb) of the detection sensitivity control unit 36.

  When the operating voltage of the transistor element Q2 of the detection sensitivity control unit 36 is Va, the sensitivity change start level as the first threshold in the detection sensitivity control unit 36 is also Va. That is, the detection sensitivity control unit 36 operates when the control signal (control signal at the point Q) that has passed through the delay unit 34 reaches Va.

  2 shows an example in which the transistor element Q2 of the detection sensitivity control unit 36 and the transistor element Q1 of the attenuation unit 30 have the same operating voltage. However, since there is a signal attenuating unit composed of resistors R1 and R2 in the previous stage of the transistor element Q1, when viewed as the attenuating unit 30, the attenuation start level Vb as the second threshold value that is the operating voltage is detected. It becomes larger than the sensitivity change start level Va of the sensitivity controller 36. Therefore, the attenuation unit 30 does not operate in the region a. That is, the detection sensitivity control unit 36 operates when a control signal that has not passed through the delay unit 34 reaches Vb. Although the circuit configuration of the attenuating unit 30 is the simplest and preferable, it is not particularly limited to this configuration. For example, an element having an operating voltage larger than the operating voltage of the transistor element Q2 may be used as the transistor element Q1. Other circuit configurations may be used.

  The detection sensitivity control unit 36 does not operate in a region a where the audio signal is small and the control signal corresponding to the audio signal is smaller than the sensitivity change start level Va of the detection sensitivity control unit 36. Therefore, the audio signal input to the attenuating unit 30 is directly amplified by the amplifying unit 14 and then output to the output terminal 12 and the detection sensitivity control unit 36 as an output signal. The output signal input to the detection sensitivity control unit 36 is output from the attenuation unit 30 via the detection sensitivity control unit 36 to the level detection unit 38 without being attenuated. The level detection unit 38 detects the level of the audio signal (signal at the point P1) output from the attenuation unit 30 and passed through the detection sensitivity control unit 36, and outputs it to the attenuation unit 30 as a control signal corresponding to the level. The control signal is delayed by the delay unit 34 and input to the detection sensitivity control unit 36. As described above, the detection sensitivity control unit 36 and the attenuation unit 30 do not operate at the level of the audio signal in the region a. Therefore, the output signal at the output terminal 12 increases as the audio signal increases as shown in the area a of FIG.

  Next, when the audio signal further increases and the control signal at the point Q corresponding to the audio signal exceeds the sensitivity change start level Va of the detection sensitivity control unit 36, the detection sensitivity control unit 36 operates to operate the point P1. AGC control is performed on the signal. By this AGC control, for example, the control signal at point P in FIG. 2 changes at a substantially constant value as shown in a region b in FIG. 5B. This control signal is input to the attenuation unit 30. However, since the attenuation start level Vb of the attenuation unit 30 is higher than the sensitivity change start level Va of the detection sensitivity control unit 36, the attenuation unit 30 does not operate, and the output signal of the output terminal 12 is in the region b of FIG. As shown, it increases with an increase in the audio signal.

  When the audio signal further increases, the transistor element Q2 reaches saturation by the resistor R3 installed in the detection sensitivity control unit 36, and the AGC control for the signal at the point P1 ends. Along with this, the control signal increases as the audio signal increases as shown in the area c of FIG. The slope of the control signal at this time is smaller than the slope of the audio signal except for the example of FIG. Since the control signal in this area c is also smaller than the attenuation start level Vb of the attenuating section 30, the attenuating section 30 does not operate and the output signal of the output terminal 12 increases as shown in the area c of FIG. It increases with it.

  As the audio signal further increases, the signal at point P1 also increases. Along with this, the control signal also increases. When this control signal exceeds the attenuation start level Vb, the attenuation unit 30 operates. In the subsequent region d, AGC control is performed on the output signal by the attenuating unit 30. As a result, the output signal is controlled to a substantially constant limit level Vmax as shown in region d of FIG. As a result, the control signal also changes substantially constant as shown in a region d in FIG.

  Next, as shown in FIG. 6A, a state in which the level of the audio signal increases sharply with time, that is, a case where sudden sounds S1 to S4 are input will be described. Note that the state in which the level of the audio signal input to the input terminal 10 increases sharply with time is that the control signal delayed by the delay unit 34 (the control signal at the point Q) starts the sensitivity change of the detection sensitivity control unit 36. It is assumed that the control signal (the signal at the point P) exceeds the attenuation start level Vb of the attenuation unit 30 before exceeding the level Va (<Vb).

  Here, a control signal component that is generated by sudden sound and whose level sharply increases as time passes is used as a sudden sound component, and the level of the sound signal gradually increases as time passes and is input to the detection sensitivity control unit 36. The signal component is the normal audio component. Since FIG. 5 shows an example in which there is no sudden sound, the control signal shown in FIG. 5B is almost equivalent to the normal sound component.

  First, when the sudden sound S1 is input in the region a, as shown in FIG. 6B, the control signal includes the sudden sound component Sa1 generated by the sudden sound S1. However, the transmission of the sudden sound component Sa1 to the detection sensitivity control unit 36 is delayed by the delay unit 34. For this reason, even if the sudden sound component Sa1 exceeds the sensitivity change start level Va, the detection sensitivity control unit 36 does not operate immediately. On the other hand, the control signal including the sudden sound component Sa1 is input to the attenuation unit 30 as it is. Therefore, before the control signal delayed by the delay unit 34 (control signal at the point Q) exceeds the sensitivity change start level Va (<Vb) of the detection sensitivity control unit 36, the control signal including the sudden sound component Sa1 is attenuated. When the start level Vb is reached, the attenuating unit 30 operates to attenuate the audio signal including the sudden sound S1. That is, if the control signal reaches the attenuation start level Vb before the delayed control signal at the point Q in FIG. 2 reaches the sensitivity change start level Va, the detection sensitivity control unit 36 does not operate and the attenuation unit 30 does not operate. Is damped. Thereby, the sudden sound S1 is attenuated to the limit level Vm1 in FIG. At this time, the fall of the sudden sound component Sa1 and the sudden sound components Sa2 and Sa3 described later become gentle due to the time constant of the level detection unit 38.

  Next, when the sudden sounds S2 and S3 are input in the region b where the AGC control is performed on the signal at the point P1, the sudden sounds S2 and S3 are attenuated according to the attenuation amount of the detection sensitivity control unit 36 at the time of occurrence. Then, they appear in the control signal as the sudden sound components Sa2 and Sa3 in FIG. At this time, the transmission of the sudden sound components Sa2 and Sa3 in the control signal is delayed by the delay unit 34. Therefore, the attenuation amount of the detection sensitivity control unit 36 does not vary greatly, and the normal sound component in the control signal does not vary greatly. On the other hand, since the control signal including the sudden sound components Sa2 and Sa3 is input to the attenuation unit 30, when the control signal including the sudden sound components Sa2 and Sa3 has reached the attenuation start level Vb, the attenuation unit. 30 operates to attenuate the audio signal including the sudden sounds S2 and S3. Thereby, the sudden sounds S2 and S3 are attenuated to the limit levels Vm2 and Vm3 in FIG. 6C, respectively. However, the limit levels Vm2 and Vm3 do not exceed Vmax.

  Next, when the sudden sound S4 of the volume level Vs is input in the area d, the attenuating unit 30 performs AGC control on the output signal in this area d, and as shown in FIG. Operates to attenuate S4. Thus, the volume restriction device 50a changes the restriction levels Vm1 to Vm3 for the sudden sounds S1 to S4 according to the level of the input audio signal.

  That is, the attenuation control unit 20 of the volume control device 50a controls the attenuation unit 30 to perform the attenuation operation in the first state in which the level of the audio signal increases sharply with time. Further, when the level of the audio signal is in the second state where the level gradually increases with time, the attenuating unit 30 is not attenuated or when the attenuating unit 30 is in the first state as in the case of the region d. Control to operate with a smaller attenuation.

  Further, the sensitivity control unit 36 of the attenuation control unit 20 moves from the attenuation unit 30 to the level detection unit 38 when the control signal delayed by the delay unit 34 exceeds the sensitivity change start level Va that is the first threshold value. Attenuates the level of the output signal. However, in the first state where the level of the audio signal sharply increases with time, the control signal delayed by the delay unit 34 does not exceed the first threshold (sensitivity change start level Va), and the attenuation unit The control signal input to 30 exceeds the second threshold value (attenuation start level Vb) larger than the first threshold value, and the attenuating unit 30 performs the attenuating operation.

  3 detects the level of the audio signal that has not passed through the detection sensitivity control unit 36, and outputs a control signal corresponding to the level. Then, when the control signal delayed by the delay unit 34 exceeds the first threshold, the detection sensitivity control unit 36 of the volume restriction device 50a in FIG. 3 attenuates the control signal. Then, the attenuating unit 30 in FIG. 3 determines the input audio signal when the control signal delayed by the delay unit 34 does not exceed the first threshold and when the control signal exceeds the second threshold. Attenuate.

  Further, when the output (control signal) of the transistor element Q3 of the volume restriction device 50a of the present embodiment according to FIG. 4 exceeds the first threshold value, the detection sensitivity control unit 36 sets the control signal to the first threshold value Va. Attenuate to

  However, in the volume restriction device 50a of the present embodiment according to FIG. 4, the delay unit 34 controls the detection sensitivity control unit 36 to attenuate the control signal to the first threshold value Va over a predetermined time. That is, the control signal is not immediately attenuated even when the first threshold value Va is exceeded, but is gradually attenuated to the first threshold value Va over a predetermined time. When the control signal reaches the operating voltage Vb of the attenuation unit 30 during the predetermined time, the attenuation unit 30 attenuates the input audio signal.

  Next, a volume restriction device 50b according to a second embodiment of the present invention is shown in FIG. The delay unit 34 of the volume restriction device 50b according to the second embodiment includes a first delay unit 34a and a second delay unit 34b. Then, the first delay unit 34a delays a signal corresponding to the audio signal (the signal at the point P1 in FIG. 7) that has passed through the detection sensitivity control unit 36 by a first time with a relatively long time constant, and performs the first control. The signal is output to the detection sensitivity controller 36 as a signal. This delays the transmission of the sudden sound component in the signal at the point P1 to the detection sensitivity control unit 36. The second delay unit 34b delays the signal corresponding to the signal at the point P1 by a second time shorter than the first time by a relatively short time constant, and transmits the signal to the attenuation unit 30 as the second control signal. . This second control signal includes a sudden sound component of the signal at the point P1. The first delay unit 34a and the second delay unit 34b each include a first level detection unit 38a and a second level detection unit 38b that detect the level of the signal at the point P1. The first level detection unit 38a may not be integrated with the first delay unit 34a, and the second level detection unit 38b may not be integrated with the second delay unit 34b. The detection sensitivity control unit 36 and the delay unit 34 operate as the attenuation control unit 20 in cooperation.

  Next, the configuration of the volume restriction device 50b will be described in more detail. FIG. 8 is a circuit diagram showing an embodiment of the volume limiting device 50b. Note that the signal at point P1 in FIG. 8 is an audio signal output from the attenuation unit 30 and passed through the detection sensitivity control unit 36, the signal at point Q1 is the first control signal, and the signal at point P2 is the second control signal. It is.

  The first delay unit 34a of the volume limiting device 50b shown in FIG. 8 is mainly composed of a diode element D2, a capacitor element C2, and a resistor R5, and these circuits function and delay as the first level detection unit 38a. It also has a function as a circuit. The second delay unit 34b is mainly composed of a diode element D1, a capacitor element C1, and a resistor R4. These circuits have a function as the second level detection unit 38b and a function as a delay circuit. Yes. Note that the lengths of the time constants of the first delay unit 34a and the second delay unit 34b, that is, the lengths of the first time and the second time are mainly determined by the capacitance values of the capacitor elements C1 and C2.

  Further, the second delay unit 34b is provided with a signal attenuating unit including resistors R1 and R2. The level of the second control signal transmitted to the attenuation unit 30 side by the operation of the signal attenuation unit is lower than that of the first control signal transmitted to the detection sensitivity control unit 36 side. Therefore, even if the operating voltage of the transistor element Q1 of the attenuation unit 30 is equal to the operating voltage of the transistor element Q2 of the detection sensitivity control unit 36, the signals input to the first and second delay units 34a and 34b respectively. If the level is used as a reference, the level of the signal at the point P1 required for the operation of the attenuation unit 30 is higher than the level at which the detection sensitivity control unit 36 operates. Therefore, when the signal at the point P1 is used as a reference, the attenuation start level Vb of the attenuation unit 30 is higher than the sensitivity change start level Va of the detection sensitivity control unit 36.

  Note that the configuration in which the signal attenuating unit including the resistors R1 and R2 illustrated in FIG. 8 is provided in the second delay unit 34b is the simplest and preferable one, but is not particularly limited to this configuration. An element having an operating voltage larger than the operating voltage of the transistor element Q2 may be used as the element Q1, or another circuit configuration may be used. Further, as shown in FIGS. 9 and 10, the amplifier A1 having a relatively small amplification factor is used as the signal line of the second delay unit 34b, and the amplifier A2 having a relatively large amplification factor is used as the signal line of the first delay unit 34a. It may be installed in.

  In addition, the detection sensitivity control unit 36 and the attenuation unit 30 of the volume restriction device 50b may be provided with a buffer amplifier Q3 separately.

  Next, the operation of the volume restriction device 50b will be described with reference to FIG. 8, FIG. 11, and FIG. For convenience of explanation, it is assumed that the influence of amplification by the amplification unit 14 and the buffer amplifier Q3 is ignored. 11 (a) and 13 (a) show an audio signal input to the input terminal 10, FIG. 11 (b) shows a first control signal (signal at point Q1 in FIG. 8), and FIG. b) shows the second control signal (the signal at the point P2 in FIG. 8). FIG. 11C and FIG. 13C show output signals at the output end 12.

  First, the case where the level of the audio signal input to the input terminal 10 gradually increases with time as shown in FIG. 11A will be described. First, in a region a where the input audio signal is small and the first control signal corresponding to the audio signal is smaller than the sensitivity change start level Va of the detection sensitivity control unit 36, the audio signal input to the attenuation unit 30 is output as it is. The signal is output to the output terminal 12 and the detection sensitivity control unit 36 as a signal. In the region a, the detection sensitivity control unit 36 does not operate because the first control signal is smaller than Va. Therefore, the output signal input to the detection sensitivity control unit 36 is output to a point P1 in FIG. 8 as an audio signal that has passed through the detection sensitivity control unit 36. The signal at the point P1 is amplified by the amplifying unit 14, and then output to the first delay unit 34a and the second delay unit 34b.

  The level of the signal at the point P1 input to the first delay unit 34a and the second delay unit 34b is detected by the first level detection unit 38a and the second level detection unit 38b, respectively. As described above, the second delay unit 34b is provided with a signal attenuating unit in front of the second level detection unit 38b, so that the level of the signal detected by the second level detection unit 38b is the first level. It becomes smaller than the level of the signal detected by the detector 38a.

  Then, the first delay unit 34a delays the signal at this point P1 for a first time, and outputs the signal to the detection sensitivity control unit 36 as a first control signal. The second delay unit 34b delays the signal at the point P1 by a second time shorter than the first time, and outputs the delayed signal to the attenuation unit 30 as a second control signal. However, as described above, the detection sensitivity control unit 36 and the attenuation unit 30 do not operate in the region a. Therefore, the output signal at the output terminal 12 increases as the audio signal increases, as shown in region a of FIG. 11 shows an example in which there is no sudden sound component, the control signal shown in FIG. 11B is equivalent to the normal sound component.

  Next, when the audio signal further increases and the first control signal based on this audio signal exceeds the sensitivity change start level Va of the detection sensitivity control unit 36, the detection sensitivity control unit 36 operates and the signal at the point P1 is detected. AGC control is performed. By this AGC control, the first control signal changes at a substantially constant value as shown in a region b in FIG. At this time, the second control signal is also substantially constant at a value smaller than the first control signal.

  Further, the second control signal at this time is input to the attenuation unit 30 via the second delay unit 34b. However, since the level of the second control signal is smaller than that of the first control signal, the second control signal does not reach the attenuation start level Vb, and thus the attenuation unit 30 does not operate. For this reason, the output signal of the output terminal 12 increases with the increase of the audio signal as shown in a region b of FIG.

  Here, FIG. 12 shows signal waveforms at various parts when the level of the audio signal that is input to the input terminal 10 gradually increases. The signal waveforms shown in the upper part of FIGS. 12A and 12B show the audio signal input to the volume limiter 50b. The signal waveform shown in the middle part of FIG. 12A indicates an output signal output from the output terminal 12. In addition, the signal waveform shown in the lower part of FIG. 12A indicates a signal at the point P1 output from the detection sensitivity control unit 36. Further, the signal waveform shown in the middle stage of FIG. 12B shows the second control signal output from the second delay unit 34b. In addition, the signal waveform shown in the lower part of FIG. 12B indicates the first control signal output from the first delay unit 34a.

  When the level of the audio signal input to the input terminal 10 increases as shown in the upper part of FIGS. 12A and 12B, the first control signal shown in the lower part of FIG. It starts to increase from the initial stage of signal increase. When the first control signal reaches a predetermined level, the first control signal changes substantially constant. In addition, the signal at the point P1 shown in the lower part of FIG. 12A also increases slightly at the initial stage of increase of the audio signal (marked with a circle in FIG. 12A), and then remains substantially constant. These signal changes show the same tendency as in FIG. Further, the second control signal shown in the middle part of FIG. 12B also has the same waveform as the first control signal. However, the level of the second control signal is lower than the level of the first control signal over the entire range due to the effect of the signal attenuating unit constituted by the resistors R1 and R2. Since the level of the second control signal is equal to or lower than the attenuation start level Vb, the attenuation unit 30 does not operate, and the output signal shown in the middle part of FIG. 12A is in the upper part of FIGS. 12A and 12B. The audio signal shown is substantially the same. This signal change shows the same tendency as in FIG.

  Next, as shown in FIG. 13A, a case where sudden sounds S1 to S3 whose levels are sharply increased with the passage of time are input to the audio signal input to the input terminal 10 will be described. First, when the sudden sound S1 is input in the area a, as shown in FIG. 13B, the second control signal includes the sudden sound component Sa1 generated by the sudden sound S1. Note that FIG. 13B shows an enlarged scale of the vertical axis so that the position of Va coincides with FIG. In addition, since the level of the sudden sound component of the first control signal and the level of the sudden sound component of the second control signal are different due to the effect of the signal attenuating unit composed of the resistors R1 and R2, For the sake of convenience, the sudden sound component of the second control signal is denoted by Sa1, and the sudden sound component of the first control signal is denoted by Sa1 '.

  The sudden sound component S1 is delayed for a first time by the first delay unit 34a having a long time constant. On the other hand, the signal at the point P1 including the sudden sound component S1 is input to the second delay unit 34b having a short time constant and transmitted to the attenuation unit 30 as the second control signal including the sudden sound component Sa1. When the second control signal including the sudden sound component Sa1 at this time reaches the attenuation start level Vb, the attenuation unit 30 operates and attenuates the audio signal including the sudden sound S1. That is, when the second control signal reaches the attenuation start level Vb before the first control signal reaches the sensitivity change start level Va, the attenuation unit 30 performs the attenuation operation without the detection sensitivity control unit 36 operating. As a result, the sudden sound S1 is attenuated to the limit level Vm1 in FIG. That is, when the sudden sound component delayed by the second time shorter than the first time reaches Vb before the first time delayed sudden sound component exceeds the sensitivity change start level Va, the detection sensitivity control unit 36 does not operate.

  Next, a case where sudden sounds S2 and S3 are input in the region b where AGC control is performed on the signal at the point P1 will be described.

  In a state where there is no sudden sound in the region b, the second control signal is maintained at a level not exceeding Vb because the signal at the point P1 is AGC controlled by the detection sensitivity control unit 36. In this state, when sudden sounds S2 and S3 occur, they are attenuated according to the attenuation amount of the detection sensitivity control unit 36, and appear as sudden sound components Sa2 'and Sa3' in the signal at the point P1. The sudden sound components Sa2 'and Sa3' are delayed by a relatively long first time in the first delay unit 34a having a long time constant. On the other hand, the signal at the point P1 including the sudden sound components Sa2 ′ and Sa3 ′ is input to the second delay unit 34b having a short time constant, delayed by a relatively short time, and includes the sudden sound components Sa2 and Sa3. The second control signal is transmitted to the attenuation unit 30. At this time, when the second control signal including the sudden sound components Sa2 and Sa3 reaches the attenuation start level Vb, the attenuating unit 30 operates to attenuate the sound signal including the sudden sound S2 and S3. Thereby, the sudden sounds S2 and S3 are attenuated to the limit levels Vm2 and Vm3 in FIG. That is, when the sudden sound component delayed by the second time shorter than the first time reaches Vb before the first time delayed sudden sound component exceeds the sensitivity change start level Va, the detection sensitivity control unit 36 does not operate.

  Here, FIG. 14 shows signal waveforms at various parts when the audio signal suddenly increases from a relatively low level to a relatively high level. The signal waveforms shown in the upper part of FIGS. 14A and 14B indicate the audio signal input to the attenuation unit 30. In addition, the signal waveform shown in the middle part of FIG. 14A indicates an output signal output from the output terminal 12. The signal waveform shown in the lower part of FIG. 14A shows the signal at the point P1 output from the detection sensitivity control unit 36. In addition, the signal waveform shown in the middle stage of FIG. 14B shows the second control signal output from the second delay unit 34b. The signal waveform shown in the lower part of FIG. 14B shows the first control signal output from the first delay unit 34a.

  As shown in the upper part of FIGS. 14 (a) and 14 (b), when the audio signal increases rapidly, sudden sound S is generated at the increased moment. This sudden sound S causes a sudden sound component in the signal at point P1. Due to this sudden sound component, the second control signal shown in the middle part of FIG. 14B immediately increases immediately after the sudden sound S occurs. This is because the delay time of the second delay unit 34b is relatively short. However, since the first delay unit 34a having a long time constant functions to delay the transmission of the sudden sound component to the detection sensitivity control unit 36, the first control signal shown in the lower part of FIG. No sound component appears. Therefore, when the sudden sound S is generated, the level of the second control signal becomes higher than the level of the first control signal and simultaneously exceeds the attenuation start level Vb. Is attenuated to a predetermined limit level.

  Then, the level of the audio signal continues to be high, whereby the first control signal input to the detection sensitivity control unit 36 gradually increases as shown in the lower part of FIG. As the first control signal increases, the detection sensitivity control unit 36 starts an attenuation operation, and the second control signal shown in the middle stage of FIG. 14B gradually decreases. When the second control signal decreases, the attenuation amount of the attenuation unit 30 decreases, and the output signal shown in the middle stage of FIG. 14A gradually increases. At time t, the level of the second control signal becomes smaller than the level of the first control signal and becomes less than the attenuation start level Vb. As a result, the attenuation operation of the attenuation unit 30 is stopped, and the audio signal and the output signal are at the same level. Further, the first and second control signals change substantially constant.

  As described above, when the first control signal delayed by the first delay unit 34a exceeds the sensitivity change start level Va, which is the first threshold, the sensitivity control unit 36 of the volume restriction device 50b attenuates the attenuation unit. The level of the signal output from 30 to the level detector 38 is attenuated. However, in the first state where the level of the audio signal sharply increases with time, the first control signal is delayed by the second delay unit 34a in a state where it does not exceed the first threshold value (sensitivity change start level Va). The second control signal exceeds the second threshold value (attenuation start level Vb) that is larger than the first threshold value, and the attenuating unit 30 performs the attenuating operation.

  Next, FIG. 15 shows output signals of the volume limiters 50a and 50b when the sudden sound S is input to the audio signal. From FIG. 15, the output signals of the volume restriction devices 50a and 50b are suppressed to the restriction level indicated by the broken line in FIG. 15 only in the region where the sudden sound S occurs in the audio signal, and are almost the same as the audio signal in the other regions. I understand that. From this, it can be seen that the volume restriction devices 50a and 50b perform the attenuation operation only when the sudden sound S occurs.

  Next, an embodiment of a sound collector according to the present invention will be described with reference to FIG. The sound collector 80 according to the present invention includes a volume limiter 50a or 50b according to each embodiment, and a sound collector 42 such as a microphone that converts external sound into an audio signal and outputs it to the input terminal 10 of the volume limiters 50a and 50b. And an audio output unit 40 such as an earphone, a headphone, or a speaker that converts an output signal from the output terminal 12 of the volume restriction devices 50a and 50b into sound. The sound collector 80 has other configurations such as an amplifier unit that amplifies output signals from the volume limiters 50a and 50b, a volume unit that increases and decreases the volume level of the output signal, and changes the output signal to the user's preference. You may provide suitably the switch etc. which switch ON / OFF of an equalizer part and the sound collector 80. FIG.

  As described above, the sound collector 80 having the volume restriction devices 50a and 50b detects the signal output from the attenuation unit to the outside of the volume restriction device, and responds to the detected level and the change in the temporal level. In order to control the operation of the attenuating unit, as shown in FIG. 17, when the sudden sound S is input in a state where the voice level Vh is relatively high in conversational speech and surrounding noise, the sudden sound S is limited. Output is attenuated and suppressed to level Vhs. When the sudden sound S is input in a state where the voice level VL has a relatively low conversational voice or ambient noise, the sudden sound S is attenuated and suppressed to a relatively low limit level VLs and output. Note that the ratio of VLs to VL and the ratio of Vhs to Vh are determined by circuit characteristics. Therefore, the relative sudden sound level increase experienced by the user is almost the same regardless of the level of the conversational voice or the ambient noise level. In other words, the volume restriction devices 50a and 50b and the sound collector 80 according to the present embodiment are not fixed in the restriction level for the sudden sound S, and suddenly depending on the surrounding sound level when the sudden sound S is input. The restriction level of the sound S is changed. Therefore, a sudden increase in volume due to sudden sound can be prevented even when the surrounding sound level is relatively low. Also, as shown in the example of FIG. 14, when a sudden loud volume such as a car whistle continues, the sudden sound generated immediately after the generation of this sound is effectively attenuated and suppressed, and then the amount of attenuation gradually increases. Operates to decrease. Therefore, the user's shock due to sudden sound can be effectively reduced regardless of the surrounding sound level.

  Moreover, since the volume limiting devices 50a and 50b and the sound collector 80 according to the present embodiment have a simple circuit configuration, the devices themselves can be provided at low cost. In particular, the volume limiter 50a and the sound collector 80 including the volume limiter 50a can be provided at an extremely low cost because the AGC circuit included in a general sound collector can be used for the volume limiter 50a. It is also useful for reducing the weight and weight. Furthermore, since the volume limiting device 50b and the sound collector 80 including the same can design the time constants of the two delay units independently, a stable circuit with few malfunctions can be designed relatively easily. Further, in addition to the absence of AGC characteristics between the input and output of the device, the volume limiting device 50b does not have an amplifier (amplifying unit 14) between the input and output. For this reason, the amplifier does not saturate and the sudden sound can be limited in a wide input voltage range. In addition, the delay unit in each embodiment delays the signal in time and also performs an operation of smoothing the signal. However, smoothing is not essential, and in each embodiment, the delay unit also performs smoothing as a more desirable configuration. As an example.

  Furthermore, the volume limiters 50a and 50b and the sound collector 80 according to the present embodiment detect a signal output from the attenuation unit to the outside of the volume limiter, and detect the detected level and a change in temporal level. Accordingly, since the operation of the attenuator is controlled, the output audio signal itself is not delayed. For this reason, there is no time lag between the voice and the actual voice, and the user does not feel discomfort.

  In the above volume limiting device 50a, an example in which the AGC characteristic is provided between the input and output of the device by setting a limit on the maximum attenuation of the detection sensitivity control unit 36 has been shown. It is good also as a structure which does not provide an AGC characteristic without setting a limit. In the above volume limiting device 50b, the example in which the AGC characteristic is not provided between the input and output of the apparatus is shown. However, the maximum attenuation amount of the detection sensitivity control unit 36 is limited and the AGC characteristic is provided between the input and output of the apparatus. It is good also as a composition.

  Further, the volume limiting devices 50a and 50b may be constituted by digital circuits. Note that the volume limiting devices 50a and 50b and the sound collector 80 are preferred examples of the present invention, so the circuit configuration of each part is of course changed, and the present invention can be changed without departing from the gist of the present invention. It is possible to implement.

20 Attenuation control unit
30 Attenuator
34 Delay part
34a First delay unit
34b Second delay unit
36 Detection sensitivity controller
38 level detector
40 Audio output unit
42 Sound collector
50a, 50b Volume limiter
80 sound collector
Va first threshold (sensitivity change start level)
Vb second threshold (attenuation start level)

Claims (5)

An attenuation unit for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit is detected and the level of the audio signal sharply increases with time, the attenuating unit controls the attenuating unit so as to attenuate the audio signal. In the second state where the level of the audio signal increases more gradually with the passage of time than in the first state, the attenuation unit does not attenuate the audio signal, or the attenuation unit An attenuation control unit that controls the attenuation unit so that an attenuation amount for attenuating the audio signal is smaller than that in the first state ,
The attenuation control unit includes:
A detection sensitivity control unit;
A level detection unit that detects a level of an audio signal output from the attenuation unit and that has passed through the detection sensitivity control unit, and outputs a control signal for controlling attenuation of the attenuation unit according to the level;
A delay unit that delays the control signal for a predetermined time,
When the control signal delayed by the delay unit exceeds a first threshold, the detection sensitivity control unit attenuates the level of the signal output from the attenuation unit to the level detection unit,
The first state is a state in which the control signal delayed by the delay unit does not exceed a first threshold, and the state in which the control signal exceeds a second threshold greater than the first threshold. features and to Ruoto amount limiting device that. An attenuation unit for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit is detected and the level of the audio signal sharply increases with time, the attenuating unit controls the attenuating unit so as to attenuate the audio signal. In the second state where the level of the audio signal increases more gradually with the passage of time than in the first state, the attenuation unit does not attenuate the audio signal, or the attenuation unit An attenuation control unit that controls the attenuation unit so that an attenuation amount for attenuating the audio signal is smaller than that in the first state ,
The attenuation control unit includes:
A detection sensitivity control unit;
A level detection unit that outputs a control signal for controlling the attenuation of the attenuation unit according to the level of the audio signal output from the attenuation unit;
A delay unit that delays the control signal that has passed through the detection sensitivity control unit for a predetermined time, and
The detection sensitivity control unit attenuates the level of the control signal when the control signal delayed by the delay unit exceeds a first threshold,
The first state is a state in which the control signal delayed by the delay unit does not exceed a first threshold, and the state in which the control signal exceeds a second threshold greater than the first threshold. features and to Ruoto amount limiting device that. An attenuation unit for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit is detected and the level of the audio signal sharply increases with time, the attenuating unit controls the attenuating unit so as to attenuate the audio signal. In the second state where the level of the audio signal increases more gradually with the passage of time than in the first state, the attenuation unit does not attenuate the audio signal, or the attenuation unit An attenuation control unit that controls the attenuation unit so that an attenuation amount for attenuating the audio signal is smaller than that in the first state ,
The attenuation control unit includes:
A delay unit;
A detection sensitivity control unit;
A level detection unit that detects a level of an audio signal output from the attenuation unit and that has passed through the detection sensitivity control unit, and outputs a control signal for controlling attenuation of the attenuation unit according to the level;
The detection sensitivity control unit attenuates the level of a signal output from the attenuation unit to the level detection unit after the control signal exceeds a first threshold value to the first threshold value,
The delay unit delays the attenuation operation of the detection sensitivity control unit so that the detection sensitivity control unit attenuates the signal to the first threshold over a first time,
The first state is a state in which the control signal exceeds a second threshold value larger than the first threshold value while the detection sensitivity control unit attenuates the signal level to the first threshold value. features and to Ruoto amount restriction device that is. An attenuation unit for attenuating the input audio signal under a predetermined condition;
When the signal output from the attenuating unit is detected and the level of the audio signal sharply increases with time, the attenuating unit controls the attenuating unit so as to attenuate the audio signal. In the second state where the level of the audio signal increases more gradually with the passage of time than in the first state, the attenuation unit does not attenuate the audio signal, or the attenuation unit An attenuation control unit that controls the attenuation unit so that an attenuation amount for attenuating the audio signal is smaller than that in the first state ,
The attenuation control unit includes:
A detection sensitivity control unit;
A level of an audio signal output from the attenuation unit and passed through the detection sensitivity control unit is detected, and a first control signal which is a signal obtained by delaying a signal corresponding to the level by a first time is output to the detection sensitivity control unit. A first delay unit to
A second control signal which is a signal obtained by detecting the level of the audio signal output from the attenuation unit and passing through the detection sensitivity control unit and delaying the signal corresponding to the level by a second time shorter than the first time is obtained. A second delay unit that outputs to the attenuation unit,
The detection sensitivity control unit attenuates the level of a signal output from the attenuation unit to the second delay unit when the first control signal exceeds a first threshold,
The first state is a state in which the second control signal exceeds a second threshold,
When the first control signal exceeds a first threshold value, the detection sensitivity control unit is configured to prevent the second control signal from exceeding the second threshold value from the attenuation unit to the second delay unit. attenuating the level of the signal output to the characteristics and to Ruoto amount limiting device. The volume restriction device according to any one of claims 1 to 4 ,
A sound collection unit that converts external sound into an electrical sound signal and inputs the sound signal to the attenuation unit of the volume restriction device;
An audio output unit that converts an audio signal output from the attenuation unit of the volume restriction device into audio;
The sound collector characterized by having.