JP3346824B2 - Voice switch device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio switch device which is closed so as to pass the audio signal when the level of the audio signal exceeds a threshold value in, for example, an intercom.

[0002]

2. Description of the Related Art Conventionally, as the above-mentioned voice switch device, for example, there is one as shown in FIG. The audio signal picked up by the microphone 2 is amplified by the amplifier 4 and then supplied to the audio switch means 6 and also to the switch control unit 8. When the level of the envelope of the input audio signal becomes equal to or higher than a predetermined threshold, the switch control unit 8 changes the control signal to, for example, H level.
Level. As a result, the audio switch means 6 is closed, and the audio signal from the amplifier 4 is transmitted to another interphone, for example. The control signal indicates that the state in which the audio signal input to the switch control unit 8 is lower than the threshold is
When the sound does not recover within a predetermined time, for example, within one second, the level is set to L level and the voice switch means 6 is opened.

[0003]

However, in the voice switch device as described above, the microphone 2 collects not only the voice signal of the speaker but also the ambient noise. Therefore, when the ambient noise is loud, there is a problem that the voice switch means 6 is closed and only the ambient noise is amplified from other interphones even though no speaker is talking.

[0004]

[0005]

The first invention has first and second microphones. The first invention further comprises two low-frequency component extracting means for extracting low-frequency components of the output signals of the first and second microphones, respectively.
There is also provided control means for generating a control signal when the difference between the envelopes of the output signals of the two low-frequency component extraction means exceeds a predetermined threshold. This control signal is supplied to the voice switch means which is interposed in the transmission path of the output signal of the first microphone and is closed according to the control signal.

The second invention has first and second microphones as in the first invention, and when a difference between envelopes of output signals of the first and second microphones exceeds a predetermined threshold value. , A first control means for generating a first control signal. Also provided is a second control means for generating a second control signal when the envelope of the output signal of the first microphone exceeds a threshold. A third control means is provided for generating a third control signal when both the first and second control signals are generated. The third control signal is supplied to the audio switch means interposed in the transmission path of the output signal of the first microphone or the difference between the output signals of the first and second microphones.

[0007]

[0008]

According to the first aspect, the output signals from the first and second microphones are supplied to low-frequency component extracting means, respectively, and the low-frequency components of both output signals are extracted. When the difference between the envelopes of these low-frequency components becomes equal to or larger than the threshold value, the control means generates a control signal, the voice switch means is closed, and the output signal of the first microphone is transmitted.

According to the second invention, when the difference between the envelopes of the first and second microphone output signals is equal to or greater than the threshold value and the envelope of the output signal of the first microphone is equal to or greater than the threshold value, the third A control signal is generated, the voice switch is closed, and the output signal of the first microphone is transmitted via the voice switch.

[0010]

FIG. 1 shows a reference example of the present invention. This reference example
For example, it relates to an intercom and has a microphone 10 for collecting a voice signal of a speaker and ambient noise. In this reference example,
It also has a microphone 12. This microphone 12
Is arranged at a distance of, for example, 30 cm from the microphone 10 and is for collecting only ambient noise.

The output signals of the microphones 10 and 12 are supplied to a difference detecting means, for example, a subtraction circuit 14, and the output signal of the microphone 12 is subtracted from the output signal of the microphone 10. As described above, the output signal of the first microphone 10 is obtained by collecting the voice signal of the speaker and the ambient noise, and the output signal of the second microphone 12 is obtained by collecting the ambient noise. , Microphone 10
The output signal of the subtraction circuit 14 obtained by subtracting the output signal of the microphone 12 from the output signal of the speaker 12 represents the voice signal of the speaker.

The output signal of the subtraction circuit 14 is supplied to a switch 16 and a switch controller 18. The switch control unit 18 detects the envelope of the output signal of the subtraction circuit 14, and supplies an H-level control signal to the audio switch unit 16 when the envelope becomes equal to or larger than a predetermined threshold.

As a result, the voice switch means 16 is closed, and only the output signal of the subtraction circuit 14, ie, the voice signal, is transmitted to another interphone or the like via the voice switch means 16. The switch control unit 18 includes the subtraction circuit 1
When the output signal of No. 4 becomes smaller than the threshold value and the state continues for a predetermined time, for example, 1 second, the control signal is set to L level.

Therefore, when the speaker talks to the microphone 10, only the voice signal is transmitted to another interphone with the ambient noise removed. When the speaker is not talking, only ambient noise is not propagated to other intercoms.

In the above reference example, the voice switch means 16
Although the output signal of the subtraction circuit 14 is supplied to the audio switch unit 16, the output signal of the microphone 10 may be supplied to the audio switch unit 16. Further, in the above reference example, the switch control unit 18 detects the envelope of the output signal of the subtraction circuit 14 and compares whether it is equal to or larger than a threshold value. However, the switch control unit 18 detects the envelope of the output signal of the microphones 10 and 12, and The difference between the envelopes may be calculated by the subtraction circuit 14, and the switch control unit 18 may compare the difference with a threshold.

An embodiment of the present invention is shown in FIGS. This embodiment is also one in which the present invention is applied to, for example, an intercom, and as shown in FIG.
have. The microphone 101 picks up a speaker's voice signal and ambient noise.
Is for collecting ambient noise, for example, a microphone 1
It is located about 30 cm away from 01.

The output signals of the microphones 101 and 121 are supplied to low-frequency component extraction means, for example, low-pass filters 20 and 22, respectively. These low-pass filters 2
0 and 22 have the same frequency characteristics. The output signal of the low-pass filter 20 is a low-frequency component of the speaker's voice signal and ambient noise as shown in FIG. 4A, and the output signal of the low-pass filter 22 is shown in FIG. Thus, it becomes the low frequency component of the ambient noise.

The low-frequency components are extracted for the following reasons. Since the microphone 121 picks up only the ambient noise instead of the audio signal, the microphone 121 is arranged away from the microphone 101. Therefore, the high frequency component of the ambient noise picked up by the microphone 121 and
There is a phase difference between the high frequency component of the ambient noise picked up by the microphone 101. Therefore, even if the difference between the output signals of the microphones 101 and 121 is detected, there is a possibility that the high-frequency components of the ambient noise cannot be sufficiently canceled. Therefore, the microphones 101 and 121 that do not generate much phase difference
By extracting only the low-frequency components of the output signal and detecting the difference between them, the ambient noise can be sufficiently canceled.

The output signals of the low-pass filters 20 and 22 are supplied to a comparison circuit 24. This comparison circuit 24
Has a subtraction circuit 141 for subtracting the output signal of the low-pass filter 22 from the output signal of the low-pass filter 20, for example, as shown in FIG.

The output signal of the subtraction circuit 141 as shown in FIG. 4C is supplied to an envelope detection circuit 26, which detects the envelope. The detected envelope, that is, the difference between the envelopes of the output signals of the low-pass filters 20 and 22 is supplied to the control signal generation circuit 28.

The control signal generating circuit 28 is provided in the circuit shown in FIG.
When the detected envelope level is equal to or higher than the threshold signal generated by the threshold signal source 30, the output signal is set to the H level as shown in FIG. The output signal changes from the H level to the L level when the state where the detected envelope level is lower than the threshold signal continues for a predetermined time, for example, 1 second or more. This output signal is supplied to the control circuit 32 shown in FIG.

The control circuit 32 is also supplied with an output signal from a voice detection circuit 34. The sound detection circuit 34 is supplied with the output signal of the microphone 101 amplified by the amplifier 36. This voice detection circuit 34
The output signal of the amplifier 36, that is, the envelope of the signal obtained by amplifying both the voice signal of the speaker and the ambient noise is detected. When the level of this envelope becomes equal to or higher than a predetermined threshold signal, the output signal of H level is output. Occurs. This output signal becomes H when the state where the detected envelope level becomes equal to or lower than the threshold signal continues for a predetermined time, for example, one second.
The level changes from the level to the L level.

The control circuit 32 generates an H-level output signal while both the output signal of the voice detection circuit 34 and the output signal of the comparison circuit 24 are at the H level. This output signal is supplied to audio switch means 161 provided on the output side of the amplifier 36. This voice switch means 161
Is closed while the output signal of the control circuit 32 is at the H level.

Therefore, in this embodiment, the level of the envelope of the difference between the low-frequency component of the ambient noise and the voice signal of the speaker and the low-frequency component of the ambient noise is equal to or higher than the threshold value, and the level of the noise is lower than the threshold. When the level of the envelope with the speaker's voice signal is equal to or higher than the threshold, the voice switch means 161 is closed, and the ambient noise and the voice signal of the speaker are switched to the voice switch means 1.
Via 61, it is supplied to another intercom.

When only ambient noise is present, the output signal of the comparison circuit 24 is at L level.
2, the voice switch means 161 is opened,
Ambient noise is not transmitted to other intercoms.

If a large noise is generated in the vicinity of the microphone 121, the noise is picked up by the microphone 121 but not picked up by the microphone 101. Therefore, the envelope of the difference between the output signals of the two microphones 101 and 121 becomes equal to or larger than the threshold, and the comparison circuit 2
4 may set the output signal to H level.

However, since the output signal of the microphone 101 does not contain much noise as described above, the level of the envelope of the output signal of the amplifier 36 does not exceed the threshold value, and the output signal of the sound detection circuit 34 has the L level. To maintain. Therefore, the output signal of the control circuit 32 also becomes L level, the voice switch means 161 is opened, and no loud noise is transmitted to another interphone.

In the above embodiment, the low-pass filter 2
Although 0 and 22 are provided, when the ambient noise does not include a high frequency component, these can be removed. In that case, the signal supplied to the audio switch means 161 may be the output signal of the subtraction circuit 141 in the comparison circuit 24 instead of the output signal of the amplifier 36. Further, in this embodiment, the envelope is detected after detecting the difference between the low frequency components of the output signals of the first and second microphones,
The difference between the envelopes of the low-frequency components is detected. After detecting the envelopes of the low-frequency components of the output signals of the first and second microphones, respectively, the difference between these envelopes is detected, and the difference between the envelopes of the low-frequency components is detected. May be detected.

[0029]

As described above, according to the first and second aspects of the present invention, the ambient noise and the voice signal are collected by the first microphone, and the ambient noise is collected by the second microphone. First
And the difference between the envelope of the output signal of the second microphone and the influence of the ambient noise can be removed.
Therefore, it is possible to prevent only ambient noise from being amplified.

Further, according to the first invention, the first and the second
Since the low-frequency components of the output signals of the microphones are extracted and the difference between the envelopes of these low-frequency components is detected, the phase difference between the high-frequency components of the ambient noise collected by the first and second microphones Even if there is, the ambient noise can be reliably removed from the difference between the envelopes of the output signals of the first and second microphones, and it is possible to reliably prevent only the ambient noise from being amplified.

Further, according to the second invention, when the difference between the envelopes of the output signals of the first and second microphones is equal to or larger than the threshold value, and when the envelope of the output signal of the first microphone is equal to or larger than the threshold value. Only the voice switch means is configured to be closed, so that even if loud noise is generated near the second microphone, it is possible to prevent the voice switch means from malfunctioning.

[Brief description of the drawings]

FIG. 1 is a block diagram of a reference example of the present invention.

FIG. 2 is a block diagram of one embodiment of a voice switch device according to the present invention.

FIG. 3 is a detailed block diagram of a comparison circuit used in the embodiment.

FIG. 4 is a waveform chart of each part of the embodiment.

FIG. 5 is a block diagram of a conventional voice switch device.

DESCRIPTION OF SYMBOLS 10 101 First microphone 12 121 Second microphone 14 Subtraction circuit (difference detection means) 16 161 Audio switch means 18 Switch control unit (control means) 20 22 Low-pass filter (low-pass component extraction means) 24 comparison circuit (first control means) 32 control circuit (third control means) 34 sound detection circuit (second control means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04M 9/10

Claims (2)

(57) [Claims] 1. A first microphone that collects an audio signal and ambient noise, a second microphone that collects the ambient noise, and low-frequency components of output signals of the first and second microphones, respectively. Two low-frequency component extracting means for performing
Control means for generating a control signal when the difference between the envelopes of the output signals of the two low-frequency component extraction means exceeds a predetermined threshold value; and the control signal interposed in the transmission path of the output signal of the first microphone. Voice switch means that is closed in accordance with the above. 2. The method according to claim 1, further comprising: a first microphone that collects an audio signal and ambient noise; a second microphone that collects the ambient noise; and a difference between envelopes of output signals of the first and second microphones. First when the threshold is exceeded
First control means for generating a control signal of the first microphone, and second control means for generating a second control signal when the envelope of the output signal of the first microphone exceeds a predetermined threshold value,
Third control means for generating a third control signal when both the first and second control signals are generated, and a transmission path for an output signal of the first microphone or a difference signal between the first and second output signals Voice switch means interposed between the first and second control signals and closed in response to a third control signal.