JPH06197396A - Audio signal amplifier - Google Patents

Abstract

PURPOSE:To provide the audio signal amplifier in which howling from a microphone is automatically eliminated. CONSTITUTION:A high frequency elimination filter means 26 is provided to a prescribed location of an audio signal amplifier and has plural different bands and eliminates a prescribed high frequency component at every band. A control means 28 compares the amplitude of the audio signal with a prescribed reference amplitude and operates a high frequency elimination filter means 26 while the band frequency is sequentially decreased when the amplitude of the audio signal exceeds the prescribed reference amplitude and does not operate the high frequency elimination filter means 26 when the amplitude of the audio signal does not exceed the prescribed reference amplitude. Thus, when the prescribed high frequency component of the audio signal is generated, the high frequency component is eliminated stepwise gradually lower from the high frequency and the listening sense is improved. Furthermore, when not generated, the high frequency component of the audio signal is not eliminated and then the sound quality is improved.

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. 11 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.
Microphone 2 which is a kind of oscillating phenomenon (annoying treble called "key") at a predetermined high frequency.
May cause howling (microphone howling).

When this microphone howling occurs, the howling state continues without any measures. For this reason, manually push the changeover switch 14 to S ₁ ,
Microphone howling is stopped by connecting a fixed howling cut filter 12 to remove high frequency components (howling frequency) from the audio signal, or by reducing the amplification of amplifiers 4, 6 and 8. It was

In order to physically stop, the distance between the microphone 2 and the speaker 10 is increased, or the microphone 2 and the speaker are used in a broadcasting studio or a recording studio.
I used to set up a soundproof partition with 10.

[0007]

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

When the howling cut filter 12 is connected to stop the howling, the howling cut filter 12 is usually left connected so that the howling does not occur thereafter.
Therefore, the high frequency part of the normal audio signal is always cut, and there is a problem that the high frequency characteristic of the microphone 2 is deteriorated.

Further, the physical method has a problem that it is visually unsightly during public broadcasting and public recording. Furthermore, since both methods are artificial operations, sometimes the howling state continues for a long time.

An object of the present invention is to solve the above problems and to provide an audio signal amplifying device capable of automatically eliminating howling of a microphone to improve sound quality.

[0011]

An audio signal amplifying device according to claim 1 is an audio signal amplifying device provided with an audio input means, an amplifier and an audio output means, and is provided at a predetermined portion of the device, and a plurality of different devices are provided. When the amplitude of the voice signal exceeds the predetermined reference amplitude, the amplitude of the voice signal is compared with a predetermined reference amplitude, and a high frequency removal filter means for removing the predetermined high frequency component for each band. Includes a control means for operating the high frequency band removing filter means by successively lowering the band frequency, and controlling the 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 that.

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. .

[0013]

According to the audio signal amplifying device of the present invention, the high frequency removing filter means is provided at a predetermined portion of the audio signal amplifying device.
It has a plurality of different bands and removes a predetermined high frequency component for each band. The control means compares the amplitude of the audio signal with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, operates the high-frequency elimination filter means by sequentially lowering the band frequency to operate the amplitude of the audio signal. When the value does not exceed the predetermined reference amplitude, the high frequency elimination filter means is controlled not to operate. Therefore, when the predetermined high frequency component of the audio signal is generated, the high frequency component is automatically and gradually removed from the high frequency in a stepwise manner, and the audibility can be improved. Further, when it does not occur, it is possible to improve the sound quality without removing the high frequency component of the audio signal.

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. Therefore, it is possible to prevent the predetermined high frequency component of the audio signal from being continuously output.

[0015]

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

The high band elimination filter means 26 is provided between the amplifier 22 and the audio output means 24, has a plurality of different bands, and removes a predetermined high band component for each band. Control means 28
Compares the amplitude of the audio signal with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, the high-frequency removing filter means 26 is operated by sequentially lowering the band, and the amplitude of the audio signal is predetermined. When it does not exceed the reference amplitude, the high frequency elimination filter means 26 is controlled so as not to operate.

FIG. 2 shows a block diagram of the device 5 when each means of FIG. 1 is specifically configured. This device 5 includes a microphone which is a voice input means, a head amplifier 4 which is an amplifier 4, a microphone amplifier 6 and a power amplifier 8, a speaker 10 which is a voice output means, a howling cut filter 50 which is a high frequency removing filter means, and a control. circuit
60 and changeover switch 70 are provided. Note that the howling cut filter 50 has a plurality of different bands (in this example, 4
Number of howling cut filters 50 ₁ , 50 ₂ , 503, 50 ₄ (removal frequency f _{C in} the order of high frequency 50 ₁ > 50 ₂ > 50 ₃
> 50 ₄ ). Further, the changeover switch 70, in addition directly from the speaker 10 of the terminal 70 _N for outputting the audio signal, in order to connect the howling cut filter 50 _1, 50 _2, 50 _3, 50 ₄ to each circuit, terminals 70 _1, It is equipped with 70 ₂ , 70 ₃ , 70 ₄ .

Here, once the problematic howling is generated, its amplitude is amplified one after another and continues to oscillate, so that the power amplifier 8 becomes saturated and the amplitude is constant at a predetermined high frequency. Become a signal. Since the amplitude of this signal is considerably larger than the amplitude of a normal voice signal, the occurrence of howling is recognized by the recognition of this signal. The present invention is based on this signal, the start signal of the control signal,
An ending signal is generated, and the howling cut filter 50 is automatically controlled by the control signal to remove howling.

Further, when the howling is removed by the howling cut filter 50, if the howling is momentarily stopped, it is unnatural to the audible sense, so that the howling sound automatically disappears (fade out). . For this reason, a plurality of howling cut filters 50 (four in this example) are provided, and the ones having a higher removal band are sequentially switched to those having a lower removal band for operation.

In FIG. 2, the control circuit 60 controls the control signals C ₁ , C ₂ and C ₂ to be given to the changeover switch 70 for sequentially switching the howling cut filters 50 ₁ , 50 ₂ , 50 ₃ , 50 ₄ .
Create C ₃ and C ₄ . As shown in FIG. 3, the circuit 60 includes a control signal generation circuit 66 (start signal generation circuit 62
And an end signal generation circuit 64), a signal continuation generation circuit 68, and a time difference signal generation circuit 80.

The start signal generating circuit 62 compares the amplitude of the voice signal with a predetermined reference amplitude, and when the amplitude of the voice signal exceeds the predetermined reference amplitude, generates a start signal of the control signal C ₁ . The end signal creating circuit 64 creates an end signal of the control signal C ₁ that continues for a predetermined time from the start signal and ends.

The time difference signal producing circuit 80 produces control signals C ₂ , C ₃ and C ₄ by shifting the time from the control signal C ₁ produced by the above circuit.

The control signals C ₁ , C ₂ , C ₃ , C ₄
Is input to the changeover switch 70, and after a predetermined time (0.6 seconds in this example) from the occurrence of howling, the howling cut filters 50 ₁ , 50 ₂ , 50 ₃ , 50 ₄ are sequentially turned on, and then a predetermined amount is turned on. OF after time (1.8 seconds in this example)
Set to F. 4 shows the start signal generating circuit 62 and FIG. 5 shows the end signal generating circuit 64. Further, FIG. 6 shows a signal continuation generating circuit 68, and FIG.

The operation of the device 5 will be described below with reference to the time chart of FIG. First, the start signal creating circuit 62 of FIG. 4 creates a start signal of the control signal C ₁ . The voice signal is integrated by the rectification / integration circuit 102 and then given to the comparator 104. The threshold of the comparator 104 is set higher than that of a normal audio signal, and if howling is not occurring, the comparator 104
Does not output anything. Here, when the howling P occurs (FIG. 8a), the rectification / integration circuit 102 outputs a waveform as shown in FIG. 8b. Then, the comparator 104,
The waveform is shaped by the inverter 106 and becomes a signal that rises (.alpha. Shown in the figure) about 0.2 seconds after the occurrence of the howling P (FIG. 8c).

Next, after this signal is inverted, the integrating circuit
108, comparator 110, inverter 112 and then integrator circuit 11
4, the signal is given to the comparator 116 and the inverter 118, and similarly becomes a signal which is further delayed by about 0.2 seconds for a total of about 0.4 seconds (FIGS. 8d and 8e). As a result, the flip-flop (FF) 120 takes out the signal Q which causes howling P and rises with a delay of approximately 0.6 seconds (β in the figure) (FIG. 8).
e). This signal β is used as the start signal of the control signal C ₁ .

Next, by the end signal generating circuit 64 of FIG.
An end signal of the control signal C ₁ is created. The 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. 8c is given to the integrating circuit 124 via the inverter 122 and integrated by a predetermined time constant (FIG. 8f). Then, the signal R is given to the comparator 126 (FIG. 8).
g). 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. 8h). On the other hand, the differentiating circuit 132 creates the signal S (raising 0.2 seconds after the howling P occurs) for creating the end signal (FIG. 8i). This signal S and the signal R of the comparator 126 are given to the OR 134 (FIG. 8j). The output of OR134 is applied to FF136 to create signal T (FIG. 8k). Then, the inverted signal U (FIG. 8m) of the signal T is given to the FF 138. After that, FF1
The output of 38 (FIG. 8n) and the signal U are given to the AND 140 to obtain the signal V (FIG. 8o). Next, this signal V is
It is 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. 8
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. 8i are given to the OR 152. And FF1
The signal W output from 54 becomes a signal which rises at the signal S and falls (γ in the figure) after a predetermined time (2.2 seconds) (Fig. 8).
q). This signal γ is used as the end signal of the control signal C ₁ .

The signal W becomes the reset signal of the FF 120 (output of FIG. 8e). This causes the FF 120 to output a control signal C ₁ which rises with a delay of about 0.6 seconds (β in the figure) and then falls in 1.8 seconds (γ in the figure) after the howling P occurs (FIG. 8r). . In this way
The control signal C ₁ is created.

About 0.6 seconds after the howling P is generated by the control signal C ₁ , the changeover switch 70
The howling cut filter 50 _1, which has the highest rejection frequency f _C in the high frequency range, is turned on by connecting to the terminal 70 ₁ of
Are removed (P _{1 in} the dotted line in FIG. 8a). Then, about 1 to howling cut filter 50 ₁ is set to ON.
After 8 seconds, the howling cut filter 50 ₁ is turned off by being connected to the terminal 70 _N of the changeover switch 70. Therefore, the audio signal is about 2.4 after the howling P occurs.
After seconds, since the outputs directly to the speaker 10 without passing through the howling cut filter 50 _1, a high frequency component of the audio signal becomes not be removed, it is possible to sound quality.

When howling occurs many times, the signal continuation generating circuit 68 of FIG. 6 is used. This circuit 68 includes FFs 156, 158, 160, 162, an OR 164, an inverter 16
Equipped with 6. The inverted signal QB of the output Q of the FF 120 includes a plurality of (4 in this example) FFs 156, 158, 160, which are connected in series.
Given to 162. This output and the output Q of FF120 are OR
When the control signal C ₁ is given to 164, a signal in which the control signal C ₁ continues four times is generated as shown in FIG. This allows
When the howling is generated continuously four times, forced in the ON state howling cut filter 50 _1, to cut the subsequent howling.

Next, the time difference signal producing circuit 80 of FIG. 7 produces control signals C ₂ , C ₃ , C ₄ for fading out howling. This circuit 80
Integrator circuit 172 (180,188), comparator 174 (182,190), F
Three sets of F176 (184,192) and OR178 (186,194) are provided as one set. The operation of the circuit 80 will be described below with reference to the time chart of FIG.

First, the control signal C ₁ (FIG. 10a) output from the FF 120 is integrated by the integrating circuit 172 (FIG. 10b) and given to the comparator 174. This output (FIG. 10c) is given to FF176. The FF 176 is reset by the signal W in FIG. 8q. The output of this FF176 (FIG. 10d) and the output of FF162 are given to OR178. The output from this OR 178 is the control signal C ₂ (FIG. 10e).

Next, the output of the FF 176 of FIG. 10d is integrated by the integrating circuit 180 (FIG. 10f) and is given to the comparator 182. This output (FIG. 10g) is given to the FF 184. The FF 184 is reset by the signal W. The output of this FF184 (Fig. 10h) and the output of FF162 are OR18.
Given to 6. The output of this OR 186 is the control signal C ₃ (FIG. 10i). Similarly, the control signal C ₄ is generated from the OR 194 (FIG. 10j). As described _{above, C 2, C 3, C} 4 to output deviates from the control signal C ₁ predetermined time is created.

These control signals are inputted to the changeover switch 70 as shown in FIG. First, as described above, the control signal C ₁ connects the howling cut filter 50 ₁ having the highest removal frequency f _C to the circuit, thereby slightly reducing the howling. Then, when the control signal C ₂ is output, the terminal 70 ₂ is connected, and the howling cut-off having the second highest removal frequency f _C is generated.
The filter 50 _2, howling is further reduced.
Similarly, the howling cut filter 50 ₃ and the howling cut filter 50 ₄ are connected in the same manner, and the howling is sequentially reduced, and finally completely removed. In this way, howling is removed so as to gradually disappear (fade out) without being instantaneously removed, and the audibility can be improved.

In this embodiment, howling is detected on the basis of 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 or 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 part of the signal path, for example, between the audio input means and the amplifier is provided. It may be provided.

[0037]

According to the audio signal amplifying device of the present invention, the high frequency removing filter means is provided at a predetermined portion of the audio signal amplifying device, has a plurality of different bands, and removes the predetermined high band component for each band. To do. The control means compares the amplitude of the audio signal with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, operates the high-frequency elimination filter means by sequentially lowering the band frequency to operate the amplitude of the audio signal. When the value does not exceed the predetermined reference amplitude, the high frequency elimination filter means is controlled not to operate. Therefore, when the predetermined high frequency component of the audio signal is generated, the high frequency component is automatically and gradually removed from the high frequency in a stepwise manner, and the audibility can be improved. Further, when it does not occur, it is possible to improve the sound quality without removing the high frequency component of the audio signal. As a result, it is possible to provide an audio signal amplifier that automatically removes howling of the microphone.

The audio signal amplifier according to claim 2 further comprises:
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 equal to or more than the predetermined number. Therefore, it is possible to prevent the predetermined high frequency component of the audio signal from being continuously output.
As a result, it is possible to provide an audio signal amplifier that automatically removes howling of the microphone.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic 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 shows a block diagram of a control circuit.

FIG. 4 is a diagram showing a start signal generation circuit. .

FIG. 5 is a diagram showing an end signal generation circuit.

FIG. 6 is a diagram showing a signal continuous generation circuit.

FIG. 7 is a diagram showing a time difference signal generation circuit.

FIG. 8 is a diagram showing a time chart of the audio signal amplifier.

FIG. 9 is a diagram showing a state in which control signals are continuously created.

FIG. 10 is a diagram showing a time chart of a time difference signal generation circuit.

FIG. 11 is a diagram showing a conventional audio signal amplifier.

[Explanation of symbols]

 20 ... Voice input means 22 ... Amplifier 24 ... Voice output means 26 ... High-frequency removal filter means 28 ... Control means

Claims (2)

[Claims] 1. An audio signal amplifying apparatus comprising an audio input means, an amplifier and an audio output means, which is provided at a predetermined portion of the apparatus and has a plurality of different bands, and a predetermined high frequency component for each band. And a high-pass removal filter means for removing the high-frequency removal filter means for comparing the amplitude of the audio signal with a predetermined reference amplitude, and when the amplitude of the audio signal exceeds the predetermined reference amplitude, the high-frequency removal filter means is operated by sequentially lowering the band frequency. An audio signal amplifying apparatus comprising: a control unit that controls the high-frequency removing filter unit not to operate when the amplitude of the audio 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: