JPH0750897A - Voice signal amplifying device - Google Patents

Abstract

PURPOSE:To provide a voice signal amplifying device which can minimize deterioration of the sound quality and can effectively eliminate the howling (prescribed high band component). CONSTITUTION:When the howling (prescribed high band component) is produced in a voice signal, a high band cut-off filter means 26 is actuated to eliminate the howling. Then the operation of the means 26 is inhibited when production of the howling is discontinued. Thus deterioration can be prevented for the high frequency characteristic and the sound quality is improved. Furthermore plural pieces of means 26 are prepared so that only the high bands are eliminated in a specific range. Thus it is possible to prevent such a case where the high band component of the voice signals are eliminated in a wide range and then to improve the sound quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal amplifier, and more particularly to microphone howling.

[0002]

2. Description of the Related Art Generally, in a broadcasting studio, a recording studio, a music performance hall, etc., a microphone is used to increase the volume of a voice or to extract only a necessary voice. When using this microphone, an audio signal amplifying device as shown in FIG. 18 is required.

This conventional device includes a microphone 2, a head amplifier 4, a microphone amplifier 6, a power amplifier 8, a speaker 10, a howling cut filter 12, and a changeover switch.
Equipped with 14. A microphone volume is connected to the output of the head amplifier 4 and a master volume is connected to the output of the microphone amplifier 6.

In this case, the entire device loop is in a positive feedback state due to the amplification factor of the device, the distance between the microphone 2 and the speaker 10, the reflected sound from the peripheral wall of the reproduced sound field, and the like.
There is a case where a kind of oscillation phenomenon (howling) occurs at a predetermined high frequency. In this case, the speaker 10 outputs an offensive high-pitched sound called "key". Once this howling occurs, it continues to output as it is without any measures.

One of the methods to prevent howling from being output,
There is a method in which the changeover switch 14 is manually moved to S ₁ and the fixed howling cut filter 12 is turned on to remove the howling (the high frequency) from the audio signal. However, this method does not stop the howling generation itself.
When 12 is turned on, it is usually left as it is.

[0006]

However, the above-mentioned audio signal amplifier has the following problems.

When howling is forcibly stopped by a method such as reducing the amplification of the amplifiers 4, 6 and 8, forget to turn the howling cut filter 12 back off and leave it on. There is a case to keep. In this case, the audio signal is always removed in the band of the howling cut filter 12, and the high frequency characteristic of the microphone 2 is deteriorated.

Further, since howling has a property of chaining in different frequency bands one after another, it is necessary to widen the removal band of the howling cut filter 12, which causes further deterioration of the frequency characteristic of the microphone. There was also.

An object of the present invention is to solve the above-mentioned problems, to minimize the deterioration of the sound quality and to effectively eliminate the howling.

[0010]

An audio signal amplifying device according to claim 1 is an audio signal amplifying device comprising an audio input means, an amplifier and an audio output means, wherein a predetermined portion of the device is provided for each predetermined high frequency band. A plurality of high frequency band removing filter means for removing the predetermined high frequency band component of the audio signal, and the predetermined high frequency band corresponding to the high frequency band removing filter means for the predetermined high frequency band of the audio signal. When the amplitude of the audio signal exceeds a predetermined reference amplitude by comparing the amplitude of the audio signal passed by the high-pass filter means with a predetermined reference amplitude and a plurality of high-pass filter means for passing the band component. A plurality of control means for operating the corresponding high frequency band removing filter means, and controlling the corresponding high frequency band removing filter means so as not to operate when the amplitude of the audio signal does not exceed a predetermined reference amplitude. It is characterized by comprising a.

The audio signal amplifying device of claim 2 is the same as that of claim 1.
In the audio signal amplifying device, the control means keeps the high frequency band removing filter means operating when the number of times the amplitude of the audio signal exceeds the predetermined reference amplitude is a predetermined number or more. .

The audio signal amplifying device of claim 3 is the same as that of claim 1.
In the audio signal amplifying device (1), each high-frequency removing filter means is connected in series.

An audio signal amplifying device according to a fourth aspect is an audio signal amplifying device including an audio input means, an amplifier and an audio output means, and is provided in a predetermined portion of the device in series for each predetermined high frequency. A plurality of high-frequency removing filter means for removing the predetermined high-frequency component of the audio signal, and a plurality of high-frequency removing filter means provided for each of the predetermined high-frequency frequencies and passing the predetermined high-frequency component of the audio signal. A plurality of high-pass filter means to be compared with the amplitude of the audio signal passed by the high-pass filter means and a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, it is dealt with. A plurality of control means for operating the high frequency band removing filter means and controlling the corresponding high frequency band removing filter means so as not to operate when the amplitude of the audio signal does not exceed a predetermined reference amplitude, and a plurality of control means. If each high band elimination filter means is operated by any means, it is characterized by comprising a loop coupling adjustment means for reducing the gain of the amplifier by a predetermined value.

[0014]

According to the audio signal amplifying apparatus of the present invention, when the predetermined high frequency component is generated in the audio signal, the high frequency removing filter means is operated to remove the predetermined high frequency component. Then, when the predetermined high frequency component is stopped, the high frequency removal filter means is not operated to prevent the deterioration of the high frequency characteristic and the sound quality can be improved.

Further, by providing a plurality of high band removing filter means, only the high band of the specific range is removed, so that the high band component of the audio signal is prevented from being removed over a wide range, and the sound quality is improved. Can be planned.

According to another aspect of the audio signal amplifying apparatus of the present invention, the control means operates the high frequency band removing filter means only when the number of times the amplitude of the audio signal exceeds the predetermined reference amplitude is a predetermined number or more. Leave it alone. Therefore, it is possible to prevent the high frequency band removing filter means from remaining operating due to the predetermined high frequency component that occurs only momentarily.

According to the audio signal amplifying device of the third aspect, the respective high frequency removing filter means are connected in series. Therefore, even when a plurality of predetermined high frequency components are generated at the same time, they can be removed by the high frequency removal filter means.

According to the audio signal amplifying device of the present invention, when a plurality of predetermined high frequency components are generated in the audio signal, each high frequency removing filter means operates to remove the predetermined high frequency components. . Then, when each high band elimination filter means is operated, the loop coupling degree adjusting means reduces the gain of the amplifier by a predetermined value. Therefore, it is possible to prevent the predetermined high frequency components from being regenerated due to chaining.

[0019]

1 shows the basic structure of an audio signal amplifier 5 according to an embodiment of the present invention. This device 5 comprises a voice input means 20 for inputting a voice signal and an amplifier for amplifying the voice signal.
22. An audio signal amplifying device having an audio output means 24 for outputting an audio signal, which comprises the following means.

The plurality of high-pass removal filter means 26 are amplifiers.
It is provided between the audio output means 24 and the audio output unit 24 for each predetermined high frequency, and removes the predetermined high frequency component of the audio signal. A plurality of high-pass filter means 30 are provided for each of the predetermined high-pass frequencies corresponding to the high-pass removal filter means 26, and pass the predetermined high-pass components of the audio signal.

The plurality of control means 28 compare the amplitude of the audio signal passed by the high-pass filter means 30 with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, the control signal is outputted. C _1, C _2, · ·, to output C _N to operate the high-frequency removing filter means 26 corresponding to the high frequency removal filter means amplitude of the audio signal corresponding to the case when it does not exceed the predetermined reference amplitude 26 Control not to operate.

FIG. 2 shows a block diagram of the device 5 when each means of FIG. 1 is configured by concrete hardware. The device 5 includes a microphone as a voice input unit, a head amplifier 4 as an amplifier 4, a microphone amplifier 6 and a power amplifier 8, a speaker 10 as a voice output unit,
A howling cut filter 50 (in this example, 50 ₁ , 50 ₂ , 50
₃ , 50 ₄ ), a bandpass filter (BPF) 55 (55 ₁ , 55 ₂ , 55 ₃ , 55 ₄ ), which is a plurality of high-pass filter means, and a control circuit 60 (60, which is a plurality of control means. ₁ , 60 ₂ , 60 ₃ , 60 ₄ ),
A changeover switch 70 (terminals 70 ₀ , 70 ₁ , 70 ₂ , 70 ₃ , 70 ₄ ) is provided.

[0023] Incidentally, the BPF55 ₁ is connected to the control circuit 60 _1, the control signal C ₁ that is created by the control circuit 60 ₁
The terminal 70 ₁ of the changeover switch 70 is connected by the output of, and the howling cut filter 50 ₁ is connected. Also,
The control circuit 60 ₂ is connected to the BPF 55 _2, and the output of the control signal C ₂ generated by the control circuit 60 ₂ connects the terminal 70 ₂ of the changeover switch 70 and the howling cut filter 50 ₂ . The same applies to BPFs 50 ₃ and 50 ₄ .

The audio signal inputted to the microphone 2, usually, since the terminal 70 ₀ of the changeover switch 70 is connected, a head amplifier 4, is amplified from the speaker 10 via the microphone amplifier 6, the power amplifier 8 Is output.

Here, it is assumed that the device 5 enters a positive feedback closed loop state and howling of the microphone 2 occurs. If this howling occurs once, its amplitude is amplified one after another and continues to oscillate, so that the power amplifier 8 becomes saturated and becomes a signal with a high frequency and large amplitude. This howling has a specific frequency depending on the amplification degree of the device, the distance between the microphone 2 and the speaker 10, and the like.

For example, as shown in FIG. 3A, if the howling P ₂ of the center frequency f ₂ occurs, the howling P _2
2 is given to each BPF 55 first.

FIG. 4a shows the pass frequency band of the BPF 55. The center frequency of BPF55 ₁ is f ₁ , BPF55 ₂
Has a center frequency of f ₂ , and BPF 55 _{3 has} a center frequency of f ₃ , B
The center frequency of PF55 ₄ is f ₄ . Therefore, the howling P ₂ in this example is taken out only from the BPF 55 ₂ (101 in the figure) and input to the control circuit 60 ₂ .

Next, in the control circuit 60 ₂ , as shown in FIG. 3b, it is judged whether or not the amplitude of the howling P ₂ exceeds the reference amplitude K. Then, if beyond the reference amplitude K, based on the howling P _2, the control signal C ₂
Is created. The output of the control signal C ₂ connects the terminal 70 ₂ of the changeover switch 70 and the howling cut filter 50 ₂ .

The rejection passband of the howling cut filter 50 is shown in FIG. 4b. As shown in this figure, the center frequency f ₁ (rejection band) of the howling cut filter 50 ₁ is set to be the same as the center frequency f ₁ (pass band) of the BPF 55 ₁ of FIG. ₂ and BPF 55 ₂ , howling cut filter 50 ₃
And BPF 55 ₃ , howling cut filter 50 ₄ and BPF
It is set similarly for 55 _4.

[0030] Accordingly, howling P ₂ of the center frequency f ₂ taken out from the BPF55 ₂ is howling cut filter 50 ₂ (shown 1 having a reject band of the center frequency f ₂
02) (Fig. 3c). BPF55 ₁ , 55 ₃ , 55 ₄
The howlings P ₁ , P ₃ and P ₄ taken out from are also similarly removed.

Next, the control circuit 60 for outputting the control signal C will be described. As shown in FIG. 5, the control circuit 60
Includes a control signal generation circuit 66 (start signal generation circuit 62 and end signal generation circuit 64) and a signal continuation generation circuit 68 for each of the control circuits 60 ₁ , 60 ₂ , 60 ₃ , 60 ₄ . The start signal creation circuit 62 compares the amplitude of the audio signal with a predetermined reference amplitude, and creates a start signal of the control signal C when the amplitude of the audio signal exceeds the predetermined reference amplitude. End signal creation circuit
The reference numeral 64 creates an end signal of the control signal C, which continues for a predetermined time from the start signal and ends. As a result, the control signal C for each control circuit 60 (60 ₁ , 60 ₂ , 603, 60 ₄ ).
(C ₁ , C ₂ , C ₃ , C ₄ ) is created.

The control signal C is input to the changeover switch 70 in FIG. 2, and the howling cut filter 50 is turned on after a predetermined time (0.6 seconds in this example) from the occurrence of the howling P, and then a predetermined time ( In this example, it is turned off after 1.8 seconds). 6 shows the start signal generating circuit 62, and FIG. 7 shows the end signal generating circuit 64. Further, FIG. 8 shows a signal continuation creating circuit 68.

The operation of the device 5 will be described below with reference to the time chart of FIG. First, in the start signal creating circuit 62 of FIG. 6, a start signal of the control signal C is created.

The audio signal is integrated in the rectification / integration circuit 102 and then given to the comparator 104. Comparator 1
The threshold of 04 is set higher than the normal audio signal, and when howling P does not occur, the comparator is set.
Nothing is output from 104. Here, when the howling P occurs (FIG. 9A), the rectification / integration circuit 102 causes
A waveform like b is output. And the comparator 10
Waveform is shaped in 4 and it takes about 0.2 after howling P occurs.
The signal rises with a delay of a second (indicated by α) (FIG. 9c).
Next, this signal is inverted by the inverter 106 and then given to the integration circuit 108, the comparator 110, the inverter 112, and then the integration circuit 114, the comparator 116, and the inverter 118,
Similarly, the signals are delayed by about 0.2 seconds each for a total of about 0.4 seconds (FIGS. 9d and 9e). As a result, the toggle flip-flop (toggle FF) 120 takes out a signal M ([beta] in the figure) which rises with a delay of about 0.6 seconds after the howling P occurs (FIG. 9e). This signal β is used as the start signal of the control signal C.

Next, by the end signal generating circuit 64 of FIG.
An end signal of the control signal C is created. This circuit
64 comprises a first stage circuit 82 and a second stage circuit 84. First, in the first stage circuit 82, the output of FIG. 9c is given to the integrating circuit 124 via the inverter 122 and integrated by a predetermined time constant (FIG. 9f). Then, the signal R is given to the comparator 126 to obtain the signal R (FIG. 9g). This signal R is given to the discharging circuit 130 via the integrating circuit 128. In the discharging circuit 130, after a predetermined time, the voltage of the capacitor of the integrating circuit 124 is discharged to turn the signal R from ON to OFF (FIG. 9h). On the other hand, the differentiating circuit 132 creates a signal S (raising 0.2 seconds after the howling P occurs) for creating the end signal (FIG. 9i). This signal S and the signal R of the comparator 126 are given to the OR 134 (FIG. 9).
j). The output of OR134 is provided to toggle FF136 to create signal T (FIG. 9k). The inverted signal U (FIG. 9m) of the signal T is given to the reset flip-flop (reset FF) 138. Then, the output of the reset FF 138 (FIG. 9n) and the signal U are given to the AND 140 to obtain the signal V (FIG. 9o). This signal V is then input to the second stage circuit 84.

In the second stage circuit 84, the signal V is given to the integrating circuit 142 and the comparator 144. This output (Fig. 9
p) is given to the integrating circuit 146, the discharging circuit 148, and the differentiating circuit 150, similarly to the first stage circuit 82. This output signal and the signal S in FIG. 9i are given to the OR 152. The signal W output from the toggle FF154 rises at the signal S,
After a predetermined time (2.2 seconds), the signal falls (γ in the figure) (FIG. 9q). This signal γ is used as the end signal of the control signal C.

The signal W serves as a reset signal for the toggle FF 120 (see FIG. 6). As a result, the toggle FF 120 outputs a control signal C which causes howling P and rises with a delay of approximately 0.6 seconds (β in the figure), and then falls in 1.8 seconds (γ in the figure) (FIG. 9r). As mentioned above,
The control signal C is created.

For example, the generated howling P ₂ is BPF 5
5 _{2 If} the input to the control circuit 60 ₂ passes, the control signal C ₂ is output, and terminals 70 _{and second} changeover switch 70 is connected, howling from howling P ₂ is generated after 0.6 seconds When the cut filter 50 ₂ is turned on, the howling P ₂ is removed (P _{E in} the dotted line in FIG. 9A). 1.8 seconds later, the howling cut filter 50 ₂ is turned off.
To be At this time, the control signals C ₁ , C ₂ , C ₃ , C
_When none of ₄ is output, in the circuit shown in FIG. 10, OR 172 outputs C _{0 and} the terminal 70 ₀ of the changeover switch 70 is connected. Therefore, after the howling P is cut, the audio signal is
Since it does not pass through the filter 50, the high frequency component of the audio signal is not removed, and the sound quality can be improved.

If the howling P continues to be generated, the signal continuation generating circuit 68 of FIG. 8 is used. The circuit 68 includes toggle FFs 156, 158, 160, 162, an OR 164, and an inverter 166. The inverted signal QB of the output Q of the toggle FF 120 is given to a plurality (four in this example) of toggle FFs 156, 158, 160, 162 connected in series. This output and the output Q of the toggle FF 120 are given to OR164, and
As shown in, a signal in which the control signal C is continuous four times is created. Thus, when the howling P are continuously generated four times, it is determined that not the howling idiopathic, the howling cut filter 50 ₁ forcibly in the ON state, to cut the subsequent howling.

Here, when a plurality of howlings having different frequency bands occur at the same time, a plurality of howlings are connected by using a switch which is connected at the same time, instead of the switch which is selectively selected like the changeover switch 70 of FIG. It is also possible to operate the cut filter 50 at the same time to remove howling.

For example, suppose that howling in the bands of the center frequency f ₂ and the center frequency f ₄ occurs at the same time. in this case,
12a by the changeover switch 72 that connects a plurality of simultaneously.
As shown in, the howling cut filter 50 ₂ and the howling cut filter 50 ₄ are simultaneously connected to the audio signal amplification circuit. At this time, the howling cut filter 50 ₂ operates to remove the band of the center frequency f ₂ (103 in FIG. 12) as shown in FIG. 12b, and the howling cut filter 50 ₄ operates to move to the center as shown in FIG. 12c. The band of the frequency f ₄ may be removed (104 in the figure).

However, in reality, the howling cut filter 50 ₂ removes howling in the band of the center frequency f ₂ but passes howling in the band of the center frequency f ₄ and the howling cut filter 50 ₄ In, the howling in the band of the center frequency f ₄ is removed, but the howling in the band of the center frequency f ₂ is passed. After all, the filter characteristic of the howling cut filter 50 becomes flat, and using only the switch 72 that connects a plurality of howling cut filters 50 at the same time does not remove howlings that occur in different frequency bands at the same time. The problem arises.

In such a case, the above problem can be solved by arranging the howling cut filters 50 in series and using the analog switch 74 for each howling cut filter 50.

FIG. 13 shows an example of the high-pass filter removing means 90 in the audio signal amplifier circuit according to the embodiment of the present invention. The howling cut filters 50 ₁ to 50 ₄ are arranged in series. In this case, the control signal C, and other controls signals C ₁ -C _4, the control signal CB ₁ to CB ₄ with a control signal C ₁ -C ₄ is inverted by the inverter 180 _{1-180 4} is used.

That is, when howling occurs, the control signals C _{1 to} C ₄ are transmitted to the analog switch 74 ₁
~ 74 ₄ output to howling cut filter 50 ₁ ~
50 ₄ starts band removal operation. On the other hand, when the howling does not occur, the control signals CB _{1 to} CB ₄ are output to the analog switches 74 ₁ to 74 ₄ and the howling cut filters 50 ₁ to 50 ₄ stop the band elimination operation.

In the above example, the howling cut filter 50 ₂ receives the control signal C ₂ , starts the band elimination operation by the analog switch 74 ₂ , and the howling cut filter 50 ₄ also receives the control signal C _4. A band elimination operation is started by the analog switch 74 ₄ . Since howling cut filters 50 ₁ and 50 ₃ do not generate howling in these bands, they receive the control signals CB ₁ and CB ₃ and stop the band elimination operation. FIG. 14 shows a state in which two howlings that occur simultaneously are removed. As shown in this figure, howling in the band of the center frequency f ₂ (shown at 105) and the center frequency f ₄
The howling of the band (shown in FIG. 106) will be removed at the same time.

The high-pass filter removing means 90 can remove the howling even when a plurality of howlings having different frequency bands occur at the same time.

On the other hand, howling has a property of chaining in different frequency bands one after another.

For example, howling P _{2 and} then P ₄ are generated, and howling cut filters 50 ₂ and 50 ₄ are turned on respectively.
This is a case in which after howling P ₂ and P ₄ are removed as N, for example howling P _{3 in} different frequency bands occurs in a chain after the howlings P ₂ and P ₄ are removed.

In such a case, in this embodiment,
The generation of a plurality of howlings P ₂ and P ₄ keeps the howling cut filters 50 ₂ and 50 _{4 in} the ON state to prevent the howling P 2 and P ₄ from outputting, and howling cut filters 50 ₂ and 50 ₄ The ON signal of 1 reduces the gain of the microphone amplifier 6 by a predetermined value (1 to 2 dB) to prevent the howling P ₃ from chaining. FIG. 15 shows an audio signal amplifier 7 according to an embodiment of the present invention.
The block diagram of is shown.

This device 7 is provided with a gain reduction signal circuit 65 and an automatic attenuator 92 in addition to the device 5 of FIG. The gain reduction signal circuit 65 is an OR94, a delay circuit 96, a reset FF98, and the automatic attenuator 92 is an analog switch.
76, resistors R ₁ and R ₂ are provided. FIG. 16 shows a time chart showing the operation of the gain reduction signal circuit 65. In addition, the device 7 has the above-mentioned howling cut.
A high frequency band removing filter means 90 in which filters 50 are arranged in series is used.

First, howling P _{2 and} then P ₄ occur (FIGS. 16a and 16b). Then, the howling cut filters 50 ₂ and 50 ₄ are controlled by the control signals C ₂ and C ₄ (see FIG. 16).
Upon receiving c, d), it is turned on and the howlings P ₂ and P ₄ are removed. The control signals C ₂ and C ₄ are given to the OR 94 of the gain reduction signal circuit 65. The output (Fig. 16)
e) is delayed by the delay circuit 96 (for example, several 100 mse).
c) is given to the reset FF98. This output (Fig. 16
f) becomes the gain reduction signal GS.

In response to the gain reduction signal GS, the analog switch 76 of the automatic attenuator 92 is tilted to the 762 side and the resistance R ₁ is connected to the microphone amplifier 6 so that the gain of the microphone amplifier 6 is ₁ to ₂ dB.
Can be lowered only. Thus, howling P ₃ after howlings P ₂ and P ₄ can be prevented from chaining.

That is, after the howling occurs, the gain of the microphone amplifier 6 is lowered so that the device 7 is changed from the closed loop in the positive feedback state to the open loop in the non-feedback state, and then the howling of different frequency bands is chained. I'm trying to prevent it from happening.

Note that, instead of the gain reduction signal circuit 65 receiving the output of the control circuit 60, a circuit 67 as shown in FIG. 17 which directly receives the output from the power amplifier 8 outputs the gain reduction signal GS when the howling occurs. You may make it output.

In this embodiment, the automatic attenuator 32 using an analog switch and a resistor is used, but an automatic attenuator driven by a motor may be used.

In this embodiment, howling is detected based on the output of the power amplifier 8. However, any part of the signal path, for example, any signal of the microphone 2, the head amplifier 4 and the microphone amplifier 6 is detected. Howling may be detected based on.

Further, in this embodiment, the high-frequency elimination filter means is provided between the amplifier and the audio output means, but any portion of the signal path, for example, between the audio input means and the amplifier is provided. It may be provided.

[0059]

According to the audio signal amplifying apparatus of the present invention, a plurality of high band removing filter means (howling cut filters) are provided.
Are provided for each predetermined high frequency (howling frequency) at a predetermined portion of the audio signal amplifier, and remove the predetermined high frequency component (howling) of the audio signal. The operation of the high frequency band removing filter means is controlled by the control means described later. A plurality of high-pass filter means (BPF) are provided for each of the predetermined high-pass frequencies corresponding to the high-pass removal filter means, and pass the predetermined high-pass components of the audio signal.

The plurality of control means compares the amplitude of the audio signal passed by the high-pass filter means with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, the corresponding high level is set. When the amplitude of the audio signal does not exceed the predetermined reference amplitude, the corresponding high frequency band removing filter means is controlled so as not to operate.

Therefore, when a predetermined high frequency component is generated in the audio signal, the high frequency removal filter means is operated to remove the predetermined high frequency component. Then, when the predetermined high frequency component is stopped, the high frequency removal filter means is not operated to prevent the deterioration of the high frequency characteristic and the sound quality can be improved.

Further, by providing a plurality of high band removing filter means, only the high band of the specific range is removed, so that the high band component of the audio signal is prevented from being removed over a wide range, and the sound quality is improved. Can be planned. As a result, it is possible to provide an audio signal amplifying device that effectively removes a predetermined high frequency component while minimizing deterioration of sound quality.

The audio signal amplifier according to claim 2 further comprises:
When the number of times that the amplitude of the audio signal exceeds the predetermined reference amplitude becomes the predetermined number of times or more, the control means keeps the high frequency band removing filter means operating. Therefore, it is possible to prevent the high frequency band removing filter means from remaining operating due to the predetermined high frequency component that occurs only momentarily. As a result, it is possible to provide an audio signal amplifying device that effectively removes a predetermined high frequency component while minimizing deterioration of sound quality.

The audio signal amplifier according to claim 3 further comprises:
Each high-pass removal filter means is connected in series. Therefore, even when a plurality of predetermined high frequency components are generated at the same time, they can be removed by the high frequency removal filter means. As a result, it is possible to provide an audio signal amplifying device that effectively removes a predetermined high frequency component while minimizing deterioration of sound quality.

In the audio signal amplifying device according to the fourth aspect, when a plurality of predetermined high frequency components are generated in the audio signal, each high frequency removal filter means operates to remove the predetermined high frequency components. Then, when each of the high frequency band removing filter means is operated, the loop coupling degree adjusting means (automatic attenuator) lowers the gain of the amplifier by a predetermined value. Therefore, it is possible to prevent the predetermined high frequency components from being regenerated due to chaining.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an audio signal amplifier according to an embodiment of the present invention.

FIG. 2 shows a block diagram of the above audio signal amplifier.

FIG. 3 is a diagram showing an example of howling P.

FIG. 4 shows a BPF 55 pass band and howling cut.
6 is a diagram showing a removal band of the filter 50. FIG.

5 is a diagram showing a configuration of a control circuit 60. FIG.

FIG. 6 is a diagram showing a start signal generation circuit 62. .

7 is a diagram showing an end signal generation circuit 64. FIG.

FIG. 8 is a diagram showing a signal continuation generation circuit 68.

FIG. 9 is a diagram showing a time chart of the audio signal amplifier.

FIG. 10 is a diagram showing a circuit for generating a control signal C ₀ .

FIG. 11 is a diagram showing a state in which control signals C are continuously created.

FIG. 12 is a diagram showing a state in which two howlings occur at the same time.

FIG. 13 shows an example of a high-pass filter removing means 90 in an audio signal amplifier circuit according to an embodiment of the present invention.

FIG. 14 is a diagram showing a state in which two howlings that occur simultaneously are removed.

FIG. 15 is a block diagram of an audio signal amplifier according to an embodiment of the present invention.

16 is a diagram showing a time chart showing the operation of the gain reduction signal circuit 65. FIG.

FIG. 17 is a diagram showing a gain reduction signal circuit 67.

FIG. 18 is a diagram showing a conventional audio signal amplifier.

[Explanation of symbols]

20 ... Voice input means (microphone) 22 ... Amplifier 24 ... Voice output means (speaker) 26 ... High frequency removal filter means (howling cut filter) 28 ... Control means 30 ... High pass filter means (BPF)

Claims (4)

[Claims] 1. An audio signal amplifying apparatus comprising an audio input means, an amplifier and an audio output means, the audio signal amplifying apparatus being provided at a predetermined portion of the apparatus for each predetermined high frequency, and removing the predetermined high frequency component of an audio signal. A plurality of high-pass removal filter means, a plurality of high-pass filter means provided corresponding to the predetermined high-pass frequency corresponding to the high-pass removal filter means, to pass the predetermined high-pass component of the audio signal, The amplitude of the voice signal passed by the high-pass filter means is compared with a predetermined reference amplitude, and when the amplitude of the voice signal exceeds the predetermined reference amplitude, the corresponding high-pass removal filter means is operated to output the voice signal. An audio signal amplifier, comprising: a plurality of control means for controlling the corresponding high-frequency removal filter means so as not to operate when the amplitude of the signal does not exceed a predetermined reference amplitude. 2. The audio signal amplifying device according to claim 1, wherein the control means keeps the high frequency band removing filter means operating when the number of times the amplitude of the audio signal exceeds the predetermined reference amplitude is a predetermined number or more. An audio signal amplifying device characterized by: 3. The audio signal amplifying device according to claim 1, wherein the respective high frequency band removing filter means are connected in series. 4. An audio signal amplifying apparatus comprising an audio input means, an amplifier and an audio output means, the audio signal amplifying apparatus being provided in series at a predetermined portion of the apparatus for each predetermined high frequency, and the predetermined high frequency component of an audio signal. A plurality of high-pass removal filter means, and a plurality of high-pass filter means provided corresponding to the high-pass removal filter means for each of the predetermined high-pass frequencies and passing the predetermined high-pass components of the audio signal. And comparing the amplitude of the audio signal passed by the high-pass filter means with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, operate the corresponding high-pass removal filter means. , When the amplitude of the audio signal does not exceed the predetermined reference amplitude, a plurality of control means for controlling the corresponding high-frequency removal filter means so as not to operate, and each high-frequency band by one of the plurality of control means. An audio signal amplifying apparatus comprising: a loop coupling degree adjusting unit that reduces a gain of the amplifier by a predetermined value when the removal filter unit is operated.