JPH0897654A - Audio signal controller - Google Patents

Abstract

PURPOSE: To obtain an audio signal controller in which surround sound is monitored while listening to a source sound and the sound volume is automatically adjusted to match the surrounding state. CONSTITUTION: A surround sound picked up by a microphone 17 is fed to a detection section 9 as a signal SM via an AGC 8 and an amplifier 5. When the level of the signal SM is higher than a prescribed level, a signal LC of a high level H is fed to a transistor(TR) 40 to light an LED 19. When a moving contact a (e) of a changeover device 21 is thrown to a contact b (f), a transistor(TR) 33 is conductive and a signal SA (SM) whose level is attenuated is fed to a variable resistor 18, and a surround sound and a source sound with a small sound volume are outputted from a headphone 25. When the changeover device 21 is thrown to the position of c (g), the signal SM is fed to a detection section 10 and when the signal SM is higher than a prescribed level, a high level H signal MC is fed to a TR 50 to make a FET 35 conductive. The level of the signal SA is increased and fed to the variable resistor 18 to increase the sound volume of the source sound. When the changeover device is thrown to the position d(h), the source sound of the signal SA is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice signal control device suitable for application to electronic equipment using, for example, headphones or earphones.

[0002]

2. Description of the Related Art Conventionally, when an electronic device such as a headphone stereo is used, it is not possible to hear the surrounding sound because the headphones are attached to the ears. For example, in order to hear an announcement in a car. Had to remove the headphones. For this reason, there is known an audio signal control device as shown in FIG. 5 in which a microphone for collecting ambient sound is provided and can be switched to an audio signal from the microphone as necessary.

In FIG. 5, reference numeral 2 is a signal processor. An antenna 3 and a magnetic head 4 are connected to the signal processing unit 2, and a radio wave received by the antenna 3 and a reproduction signal obtained by reproducing a magnetic tape (not shown) with the magnetic head 4 are converted into a source audio signal SA. To be done. The source audio signal SA is supplied to the fixed terminal on the a side of the signal switch 6.

Reference numeral 17 is a monitor microphone for collecting ambient sounds. A microphone amplifier section 5 is connected to the monitor microphone 17, and the microphone signal SMIC output from the monitor microphone 17 is amplified by the microphone amplifier section 5 to be a microphone audio signal SM. The microphone voice signal SM is supplied to the fixed terminal on the b side of the signal switch 6.

The movable terminal of the signal switch 6 is a volume 18
The source audio signal SA or the microphone audio signal SM selected by the signal switch 6 is supplied to the volume 18 which is connected to one of the terminals. The other terminal of the volume 18 is grounded, and the mover is connected to the power amplifier section 7. Headphones 25 are connected to the power amplifier section 7.

When listening to a source sound such as a radio sound or a tape reproduction sound in the audio signal control device thus constructed, the movable terminal of the signal switch 6 is set to the a side and the source audio signal SA is sent to the volume 18. Supplied. The supplied source audio signal SA is set to a predetermined signal level by the volume 18, and then amplified by the power amplifier section 7 to be a source audio output signal SAO. The source audio output signal SAO was supplied to the headphones 25 to listen to the source audio.

When listening to the ambient sound, the movable terminal of the signal switch 6 is set to the side b and the microphone sound signal SM is supplied to the volume 18. The supplied microphone sound signal SM is set to a predetermined signal level by the volume 18, and then amplified by the power amplifier section 7 to be a microphone sound output signal SMO. The microphone sound output signal SMO was supplied to the headphones 25, and the surrounding sounds were heard while the headphones 25 were worn.

[0008]

By the way, in the above-described conventional audio signal control device, since the signal switching device 6 selects the source audio signal SA and the microphone audio signal SM by switching, the ambient sound is generated. I couldn't hear the source audio when I listened to with headphones.

Further, if the ambient noise becomes loud while listening to the source sound output from the headphones 25, the volume 18 is operated in accordance with the surrounding conditions to make the source sound easier to hear. It was necessary to make adjustments, and the operation of the volume 18 was complicated.

Therefore, the present invention provides an audio signal control device capable of monitoring the surrounding sound while listening to the source sound and automatically adjusting the volume according to the surrounding situation.

[0011]

A voice signal control device according to the invention of claim 1 is a signal attenuating means for attenuating a signal level of an input voice signal, a microphone section, and an input voice signal or a microphone section. And a signal switching means for switching whether to add and output the microphone signal from the input audio signal whose signal level is attenuated by the signal attenuating means.

According to a second aspect of the present invention, there is provided a voice signal control device for outputting a signal attenuating means for attenuating the signal level of an input voice signal, a microphone section, and a detection signal corresponding to the signal level of the microphone signal from the microphone section. Level detecting means for changing the signal level of the input audio signal according to the detection signal from the level detecting means, and outputting the input audio signal or a signal from the microphone signal and the signal attenuating means from the microphone part. There is provided a signal switching means for switching between adding and outputting the input audio signals whose levels are attenuated or outputting the input audio signal whose signal level is changed by the level changing means.

An audio signal control device according to a third aspect of the present invention includes display means for detecting a signal level of a microphone signal from a microphone section and displaying when the signal level exceeds a predetermined level.

[0014]

According to the first aspect of the present invention, either the input voice signal is output from the signal switching unit or the addition signal of the microphone signal from the microphone unit and the input voice signal attenuated by the signal attenuating unit is switched and output. . Therefore, for example, when the present invention is used for a headphone stereo, not only can the source sound be heard with the headphones, but also surrounding sounds such as an in-vehicle announcement can be heard with the headphones, and the surrounding sound such as an in-vehicle announcement can be heard. It is possible to check the source sound even while listening with headphones.

According to the second aspect of the present invention, the level of the input voice signal, the addition signal of the microphone signal and the input voice signal attenuated by the signal attenuating means, or the detection signal corresponding to the signal level of the microphone signal from the microphone unit is set. One of the input audio signals whose signal level is changed by being supplied from the detecting means to the level changing means is output from the signal switching means. Therefore, for example, when the present invention is used for a headphone stereo, not only can the source sound be heard with the headphones, but also surrounding sounds such as an in-vehicle announcement can be heard with the headphones, and the surrounding sound such as an in-vehicle announcement can be heard. You can check the source audio even while listening through headphones.
Furthermore, since the volume of the source sound output from the headphones can be automatically controlled according to the volume of ambient noise without operating the volume, operability can be improved.

According to the third aspect of the present invention, when the signal level of the microphone signal from the microphone unit exceeds a predetermined level, the display is displayed on the display means. Therefore, when the present invention is applied to a headphone stereo, it is possible to easily confirm the surrounding sound condition by visually observing the display means even when the source sound is being heard by the headphone.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a voice signal control device according to the present invention will be described below with reference to the drawings. The embodiment shows the case where the audio signal control device is used for a headphone stereo, and FIG. 1 shows the appearance of the embodiment.

In FIG. 1, reference numeral 1 is a headphone stereo main body, and 15 is a remote control operation unit. Reference numeral 25 is a headphone. The remote control operation unit 15 includes an operation unit 16 that controls tape driving operation of a headphone stereo, a monitor microphone 17 that collects ambient sound, a volume 18 that adjusts the volume of the headphones 25, and a display element (for example, a light emitting diode) 19. , A signal switch 20 (21) is provided.

Next, the configuration of the first embodiment of the audio signal control device according to the present invention will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, the source audio signal SA output from the signal processing unit 2 is composed of two signal switching units 20A and 2A.
0B is supplied to the movable terminal d of the switching unit 20B of the signal switch 20. Further, the microphone sound signal SM output from the microphone amplifier unit 5 is the switching unit 20A of the signal switch 20.
Is supplied to the movable terminal a. The switching unit 20A and the switching unit 20B of the signal switching device 20 are interlocked with each other. When the movable terminal a of the switching unit 20A is set to the b side, the movable terminal d of the switching unit 20B is set to the e side and the movable terminal is set to the movable terminal d. When a is on the c side, movable terminal d is on the f side.

The fixed terminal on the b side of the switching unit 20A and the fixed terminal on the f side of the switching unit 20B are connected to the terminals of the volume 18 which are not grounded. The fixed terminal on the e side of the switching unit 20B is connected to the non-grounded terminal of the volume 18 via the resistor 31, and the fixed terminal on the c side of the switching unit 20A is opened.

In the audio signal control device thus constructed, when the source audio is heard, the movable terminals a and d of the signal switch 20 are set to the c side and the f side, respectively. At this time, the source audio signal SA is supplied to the volume 18, so that the source audio output signal SAO is transmitted to the headphones 25.
You can listen to the source voice supplied to.

When listening to ambient sounds, the movable terminals a and d of the signal switch 20 are set to the b side and the e side, respectively.
At this time, since the microphone sound signal SM and the attenuated source sound signal SAD whose signal level is attenuated by the resistor 31 are supplied to the volume 18, the microphone sound output signal SMO and the attenuated source sound output signal SADO are supplied to the headphones 25. Thus, the source sound can be heard along with the surrounding sounds. Since the volume of the source sound is attenuated, it is easy to hear the surrounding sound, and the source sound can be confirmed while listening to the surrounding sound. Further, since the monitor microphone 17 is arranged in the remote controller operating unit 15 as shown in FIG. 1, ambient sounds can be collected with high sensitivity.

Next, a second embodiment will be described with reference to FIG. In FIG. 3 as well, portions corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 3, the source audio signal SA output from the signal processing unit 2 is supplied to the volume 18 via a series circuit of resistors 31, 34 and 36.

One terminal of the resistor 32 is connected to the connection point between the resistor 31 and the resistor 34. The other terminal of the resistor 32 is connected to the collector of the NPN transistor 33.
Grounded through the emitter. The base of the transistor 33 is connected to the fixed terminal on the f side of the switching unit 21B of the signal switching unit 21 having the two signal switching units 21A and 21B. In addition, the switching unit 21A and the switching unit 2 of the signal switching unit 21.
1B is interlocking, and the movable terminal a of the switching unit 21A
Is set to the b side, the movable terminal e of the switching unit 21B is set to the f side. When the movable terminal a is on the c side, the movable terminal e is g
When the movable terminal a is set to the d side, the movable terminal e is set to h
To be on the side.

The resistor 34 is connected to one terminal of the resistor 34.
The source of the FET 35 for short-circuiting is connected, and the drain of the FET 35 is connected to the other terminal of the resistor 34. The gate of the FET 35 is a resistor 37.
Grounded through.

Also, the monitor microphone 17 is an AGC circuit 8
The microphone signal SMIC from the monitoring microphone 17 is supplied to the microphone amplifier section 5 with its signal level controlled by the AGC circuit 8. The microphone sound signal SM output from the microphone amplifier section 5 is supplied to the movable terminal a of the switching section 21A and the level detecting section 9.

The AGC circuit 8 and the base of the NPN transistor 40 for driving the light emitting diode are connected to the level detecting section 9, and it is determined that the signal level of the microphone sound signal SM exceeds the first detection level. When detected by the detection unit 9, the high level “H” level detection signal LC is supplied to the base of the transistor 40.

The collector of the transistor 40 is connected to the cathode of the light emitting diode 19 via the current limiting resistor 41, and the anode of the light emitting diode 19 is connected to the power supply terminal 43. The emitter of the transistor 40 is grounded.

Here, for example, when the first detection level is set to a level slightly higher than the signal level of the microphone audio signal SM based on the ambient noise, an in-vehicle announcement or the like having a louder volume than the ambient noise is output to the monitor microphone. When the sound is collected at 17, the level detection unit 9 detects that the microphone sound signal SM based on the announcement sound exceeds the first detection level. At this time, the level detection unit 9 supplies the high-level “H” detection signal LC to the base of the transistor 40, and the transistor 40 is turned on. Therefore, a predetermined current is supplied to the light emitting diode 19 and the light emitting diode 19 is turned on.

As described above, when an announcement sound having a volume higher than the ambient noise is generated, the light emitting diode 19 is automatically turned on to function as a sound sensor, so that headphones or earphones are attached to the ears. Even in the state, it is possible to easily visually confirm that the announcement sound or the like is generated.

When the level detector 9 detects that the signal level of the microphone audio signal SM exceeds the second detection level, which is larger than the first detection level, the high level is detected. The “H” level detection signal GC is supplied to the AGC circuit 8.

Here, for example, when the second detection level is set to the maximum signal level of the microphone voice signal SM which does not cause distortion of the microphone sound, when a loud announcement sound is collected by the monitor microphone 17. The level detection unit 9 detects that the microphone sound signal SM based on the announcement sound exceeds the second detection level. At this time, the high-level “H” detection signal GC from the level detector 9 is sent to the AGC circuit 8.
Is supplied to. In the AGC circuit 8, the signal level of the microphone signal SMIC is attenuated by a predetermined level based on the high-level “H” detection signal GC and supplied to the microphone amplifier unit 5. Therefore, even if a loud announcement sound is collected by the monitor microphone 17, the microphone sound is not distorted and can be easily heard from the headphones 25.

The fixed terminal on the b side of the switching portion 21A is
It is connected to the volume 18 via the resistor 45. Further, the fixed terminal on the c side is connected to the level detection unit 10, and the fixed terminal on the d side is opened.

In the level detection section 10, when the signal level of the signal supplied via the fixed terminal on the c side exceeds a predetermined detection level, the level detection signal MC of high level "H" is output.
Is supplied to the base of the NPN transistor 50 for controlling the level of the source audio signal SA. The level detector 1
A volume 55 for varying the detection level is connected to 0. One terminal of the volume 55 is connected to the power supply terminal 56 and the other terminal is grounded, and the voltage level signal of the mover is supplied to the level detection unit 10 and detected based on this voltage level signal. The level is set.

The base of the transistor 50 is grounded via the capacitor 51. The emitter of the transistor 50 is grounded and the collector is connected to the base of the PNP transistor 52. This transistor 52
The emitter is connected to the power supply terminal 53, and the collector is connected to the gate of the FET 35 described above.

The movable terminal e of the switching section 21B is connected to the power supply terminal 54, and the fixed terminals on the g side and the h side are opened.

The present example is configured in this way, and the operation will be described next. First, when listening to the source voice, the movable terminal a of the switching unit 21A of the signal switching device 21 is set to the d side and the movable terminal e of the switching unit 21B is set to the h side. At this time, the transistor 33 is turned off. Further, since no signal is supplied to the level detection unit 10, the level detection signal MC is set to the low level “L” and the transistor 5
0, the transistor 52, and the FET 35 are turned off. Therefore, the volume 18 has the signal processing unit 2
The source audio signal SA output from the resistors 31 and 3
Since it is supplied via 4, 36, the source sound output signal SAO is supplied from the power amplifier unit 7 to the headphones 25, and the source sound can be heard.

Next, when listening to the ambient sound, the switching unit 21A
And the movable terminal e of the switching unit 21B is set to the f side. At this time, the transistor 33 is turned on, so that the signal level of the source audio signal SA supplied from the resistor 31 to the resistor 34 is attenuated by a predetermined amount. Further, since no signal is supplied to the level detection unit 10, the level detection signal MC is set to the low level “L”, so that the transistor 50, the transistor 52, the FET 3
5 is turned off. Therefore, the volume sound 18 is supplied with the microphone sound signal SM output from the microphone amplifier unit 5 and the source sound signal SAD whose signal level is attenuated due to the transistor 33 being turned on. To microphone audio output signal S
The MO and the attenuated source audio output signal SADO are supplied to the headphones 25 so that the source audio can be heard together with the ambient sound. Since the volume of the source voice is attenuated, it is easy to hear the surrounding sound, and the source voice can be confirmed while listening to the surrounding sound.

By the way, the movable terminal a of the switching section 21A is changed to c
When the movable terminal e of the switching section 21B is set to the g side, the microphone sound signal SM output from the microphone amplifier section 5 is supplied to the level detection section 10 and the transistor 33 is turned off. Here, when the signal level of the microphone audio signal SM output from the microphone amplifier unit 5 does not exceed the predetermined detection level, the level detection signal MC is set to the low level “L” and the transistor 50, the transistor 52,
The FETs 35 are turned off. Therefore, as in the case of listening to the above-mentioned source voice, the source voice output signal SAO is supplied from the power amplifier unit 7 to the headphones 25, and the source voice can be heard.

When ambient noise increases while listening to the source voice, the signal level of the microphone voice signal SM output from the microphone amplifier section 5 exceeds a predetermined detection level, and the level detection section 10 outputs a high level "H". Level detection signal MC ”is output. The high level “H” detection signal MC causes the transistors 50 and 5 to
2, the FET 35 is turned on and the resistor 34 is turned on.
Are short-circuited. Therefore, the source audio signal SAU whose signal level is increased is supplied to the volume 18, and the source audio output signal SAUO whose signal level is increased is supplied from the power amplifier section 7 to the headphones 25.
Even if the ambient noise is loud, the source voice can be easily heard.

Even if a pulsed noise sound is collected by the monitoring microphone 17 and a pulsed high level “H” level detection signal MC is supplied from the level detection section 10 to the base of the transistor 50, Capacitor 51 on the base
, The transistor 50 is never turned on. Therefore, the source sound with a stable volume can be output from the headphones 25 without being affected by the noise sound. If the level detection signal MC supplied to the base of the transistor 50 has a time constant, the volume of the source sound can be changed more smoothly.

As described above, according to the present embodiment, when an announcement sound having a volume louder than the ambient noise is generated while listening to the source sound, the light emitting diode arranged in the remote controller operation unit 15 is used. Since the light emitting diode 19 is automatically turned on, it is possible to easily confirm that an announcement sound or the like is generated even when headphones or earphones are worn in the ear. Further, since the source sound whose volume is attenuated can be heard while listening to the surrounding sound such as the announcement sound, the source sound can be heard without interruption. Furthermore, when the ambient noise increases while listening to the source voice, the volume of the source voice is automatically increased, so that the source voice can be heard well.

Next, a third embodiment will be described with reference to FIG. Also in FIG. 4, parts corresponding to those in FIGS. 3 and 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 4, the resistor 34 is replaced by the resistor 6
1 and the source / drain series circuit of the FET 63 and the resistor 62 and the source / drain series circuit of the FET 64 are connected in parallel.

The fixed terminal on the c side of the switching section 21A is connected to the comparator section 11. In the comparator section 11, when the signal level of the signal supplied through the fixed terminal on the c side exceeds the first detection level, the high level “H” is output.
Level detection signal FC1 is supplied to the gate of the FET 63. When the second detection level, which is higher than the first detection level, is exceeded, the high-level “H” level detection signal FC2 is supplied to the FET 64.

The movable portion a of the switching portion 21A of the voice signal control device thus configured is set to the c side, and the switching portion 2
Assuming that the movable terminal e of 1B is on the g side, the comparator unit 11
The microphone audio signal SM output from the microphone amplifier 5
Is supplied and the transistor 33 is turned off. Here, when the signal level of the microphone audio signal SM output from the microphone amplifier unit 5 does not exceed the first and second detection levels, the level detection signals FC1, FC
Since 2 is at low level "L", the FETs 63 and 64 are turned off. Therefore, the source audio signal SA output from the signal processing unit 2 is generated by the resistors 31, 3
By being supplied to the volume 18 via 4, 36, the source sound output signal SAO is supplied to the headphones 25 and the source sound can be heard.

When the ambient noise increases while listening to the source voice, the signal level of the microphone voice signal SM output from the microphone amplifier unit 5 exceeds the first detection level and the level detection signal of the high level "H". FC1 is FET6
Since it is supplied to the base of FET 3, the FET 63 is turned on and the resistor 61 is connected in parallel with the resistor 34. Therefore, the source audio signal SA supplied to the volume 18 is
The signal level of is increased and the volume of the source sound from the headphones 25 is automatically increased.

When the ambient noise becomes louder,
Since the signal level of the microphone audio signal SM output from the microphone amplifier unit 5 exceeds the second detection level and the high level “H” level detection signal FC2 is supplied to the base of the FET 64, the FET 64 is turned on. The resistor 62 is connected in parallel to the parallel circuit of the resistor 34 and the resistor 61. Therefore, the signal level of the source audio signal SA supplied to the volume 18 is further increased, and the volume of the source audio from the headphones 25 is further increased.

The switching units 21A, 2 of the signal switching unit 21.
In the case where the movable terminals a and e of 1B are set to the b side and the f side, respectively, and the movable terminals a and e of the switching units 21A and 21B are set to the d side and the h side, respectively, the second embodiment described above is used. The operation is performed in the same manner as, and detailed description thereof will be omitted.

As described above, according to this embodiment, when the ambient noise becomes loud while listening to the source voice, the volume of the source voice is automatically adjusted to an appropriate level according to the ambient noise level. Since the level is controlled, the listening of the source voice can be further improved.

The level detection in the comparator section 11 is not limited to two stages, but may be three or more stages. Further, the comparator section 11 and the resistors 34, 61, 6
2, a gain control amplifier is used in place of the FETs 63 and 64, and the source audio signal SA is supplied in accordance with the signal level of the signal supplied through the fixed terminal on the c side of the switching unit 21A.
The signal level of may be controlled. Further, the impedance variable element may be used to control the signal level of the source audio signal SA according to the signal level of the signal supplied via the fixed terminal on the c side of the switching unit 21A.

Further, the present invention can be applied not only to a headphone stereo but also to a case of listening to audio from a compact disc reproducing device, a mini disc reproducing device, a television or the like with headphones or earphones.

[0055]

According to the invention of claim 1, either the input voice signal is switched from the signal switching means, or the addition signal of the microphone signal from the microphone part and the input voice signal attenuated by the signal attenuating means is switched. Is output. Therefore, for example, when using the present invention for headphone stereo,
Not only can you hear the source sound with headphones, but you can also hear the surrounding sounds such as in-vehicle announcements with the headphones, and you can check the source sound even while listening to the surrounding sounds such as in-car announcements with the headphones. it can.

According to the invention of claim 2, the input voice signal,
Alternatively, the addition signal of the microphone signal and the input audio signal attenuated by the signal attenuating unit, or the detection signal corresponding to the signal level of the microphone signal from the microphone unit is supplied from the level detecting unit to the level changing unit, so that the signal level is changed. One of the varied input audio signals is output from the signal switching means. Therefore, for example, when the present invention is used for a headphone stereo, not only can the source sound be heard with the headphones, but also surrounding sounds such as an in-vehicle announcement can be heard with the headphones, and the surrounding sound such as an in-vehicle announcement can be heard. You can check the source audio even while listening through headphones. Furthermore, since the volume of the source sound output from the headphones can be automatically controlled according to the volume of ambient noise without operating the volume, operability can be improved.

According to the third aspect of the present invention, when the signal level of the microphone signal from the microphone section exceeds a predetermined level, the display is displayed. Therefore, when the present invention is applied to a headphone stereo, the state of surrounding sounds can be easily confirmed by visually observing the display means even when the source sound is being heard by the headphones.

[Brief description of drawings]

FIG. 1 is a diagram showing an external appearance of an embodiment of an audio signal control device according to the present invention.

FIG. 2 is a diagram showing a configuration of a first exemplary embodiment.

FIG. 3 is a diagram showing a configuration of a second exemplary embodiment.

FIG. 4 is a diagram showing a configuration of a third exemplary embodiment.

FIG. 5 is a diagram showing a configuration of a conventional audio signal control device.

[Explanation of symbols]

 1 headphone main body 2 signal processing unit 3 antenna 4 magnetic head 5 microphone amplifier unit 6, 20, 21 signal switching unit 7 power amplifier unit 8 AGC circuit 9, 10 level detection unit 11 comparator unit 15 remote control operation unit 16 operation unit 17 for monitoring Microphone 18,55 Volume 19 Display element 20A, 20B, 21A, 21B Switching unit 25 Headphones

Claims (3)

[Claims] 1. A signal attenuating unit for attenuating the signal level of an input audio signal, a microphone unit, and outputting the input audio signal, or a microphone signal from the microphone unit and the signal level being attenuated by the signal attenuating unit. And a signal switching means for switching whether to add and output the input audio signals. 2. A signal attenuating unit for attenuating the signal level of an input audio signal, a microphone unit, a level detecting unit for outputting a detection signal corresponding to the signal level of the microphone signal from the microphone unit, and the level detecting unit. Level varying means for varying the signal level of the input audio signal in accordance with the detection signal from, and the signal level is attenuated by the microphone signal from the microphone part and the signal attenuating means by outputting the input audio signal. An audio signal control device comprising signal switching means for switching between adding and outputting input audio signals or outputting an input audio signal whose signal level is changed by the level changing means. 3. A display unit for detecting a signal level of a microphone signal from the microphone unit and displaying when the signal level exceeds a predetermined level.
Alternatively, the audio signal control device according to claim 2.