JP2007174011A - Sound pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute sound pickup with a high S/N ratio without damaging frequency characteristics even in a state in which a sound source moves. <P>SOLUTION: An output signal synthesizer 30 synthesizes and outputs a final digital audio signal SS from digital audio signals S-k (k=1-m) obtained by microphones 11-k (k=1-m). Extractors 20-k (k=1-m) output sound strength signals Es-k (k=1-m) from the digital audio signals S-k (K=1-m). A switching control unit 40 controls the output signal synthesizer 30 on the basis of the sound strength signals Es-k (K=1-m), so that a signal is outputted high in strength of a sound component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sound collection device that collects external sounds and outputs an electrical signal.

In order to collect a speaker's voice in a noisy environment such as an audio conference, a sound collection device that collects a voice emitted from the speaker's mouth as a sound source with a high S / N ratio is required. . As techniques for meeting these demands, Patent Documents 1 and 2 propose a technique of combining microphones having unidirectionality and outputting the output signals of the microphones in a superimposed manner.
Japanese Patent Laid-Open No. 10-126876 JP 2000-188895 A

  According to the techniques disclosed in Patent Documents 1 and 2 described above, only when sound is generated from a specific position or direction, output signals of the microphones that pick up the sound are superimposed and output in phase. . Therefore, it is possible to focus on the voice uttered from the speaker's mouth, which is a sound source, and collect the voice with a high S / N ratio. However, it is difficult to superimpose the output signals of a plurality of microphones in the same phase over a wide frequency band. For this reason, when sound collection is performed by the techniques disclosed in Patent Documents 1 and 2, there is a problem that the frequency characteristics of the collected sound are impaired. Further, the techniques disclosed in Patent Documents 1 and 2 collect sound generated from a sound source with a high S / N ratio when the position of the sound source moves, such as when the position of the speaker's mouth moves. There is a problem that it is difficult to do.

  The present invention has been made in view of the circumstances described above, and provides a sound collection device capable of collecting sound with a high S / N ratio without impairing frequency characteristics even when the sound source moves. The purpose is to do.

The present invention includes a plurality of microphones that collect sound from the outside world and output an electrical signal, output signal synthesis means that synthesizes and outputs an audio signal to be output from each output signal of the plurality of microphones, Extracting means for extracting at least a sound component from each output signal of the plurality of microphones and outputting a signal indicating the intensity or S / N ratio of the sound component of each signal, and based on the output signal of the extracting means, A switching control means for executing a switching control process for controlling the output signal synthesizing means so that a signal having a high sound component intensity or a high S / N ratio among the output signals of the microphones is output by the output signal synthesizing means; Provided is a sound collecting device.
According to this invention, the output signal synthesizing means outputs a signal having a large intensity or a high S / N ratio among the output signals of the plurality of microphones. Therefore, even in a situation where the sound source moves, sound generated from the sound source can be collected with a high S / N ratio without impairing frequency characteristics.

Embodiments of the present invention will be described below with reference to the drawings.
<Configuration of Embodiment>
FIG. 1 is a block diagram showing a configuration of a sound collecting apparatus according to an embodiment of the present invention. As illustrated in FIG. 1, the sound collection device according to the present embodiment includes m microphones 11-k (k = 1 to m). 2 and 3 show examples of mounting the microphone 11-k (k = 1 to m) in the sound collecting device, respectively. In these drawings, an example in which the number m of microphones is 3 is shown.

  The sound collection device according to the present embodiment may be configured as an independent device or may be incorporated into another device. FIG. 2 shows a mounting example of a microphone in the sound collecting apparatus which is the former example. In this sound collecting device, three microphones 11-1 to 11-3 are fixed to a horizontal bar 502 fixed to the top of a stand 501. FIG. 3 shows, as the latter example, a microphone mounting example in a notebook personal computer in which the sound collecting device according to the present embodiment is incorporated. In this example, three microphones 11-1 to 11-3 are fixed to the upper part of the display 503 of the notebook computer.

  The microphone 11-k (k = 1 to m) used in the present embodiment is a unidirectional microphone whose sound receiving sensitivity depends on the direction of arrival of sound. In the example shown in FIG. 2 and FIG. 3, assuming that the axis oriented in the direction in which the maximum sound receiving sensitivity is obtained in the microphone is called the maximum sensitivity axis, each of the microphones 11-1 to 11-3 has the maximum sensitivity axis. The sound pickup device or notebook computer is directed to the right, right front, and left diagonal directions. As described above, the m microphones 11-k (k = 1 to m) in the present embodiment are fixed to the sound collection device so that each maximum sensitivity axis draws radiation.

  The speaker speaks in front of these microphones 11-k (k = 1 to m). When the speaker moves, a microphone suitable for picking up the voice of the speaker is selected. It changes according to the position. For example, in the example shown in FIGS. 2 and 3, when the speaker's mouth is on the left side of the sound pickup device or the notebook computer, the microphone 11-1 having the maximum sensitivity axis directed in the direction of the speaker's mouth. This output signal is suitable for indicating the speaker's voice. However, when the speaker changes posture and the speaker's mouth moves directly in front of the microphone 11-2, the level of the output signal of the microphone 11-2 becomes maximum, and this output signal is adopted as an indication of the speaker's voice. You should do it.

  Therefore, in the sound collection device according to the present embodiment, the level of the sound component of each output signal of the microphone 11-k (k = 1 to m) is monitored, and in principle, the signal of the maximum level is selected to obtain the final digital signal. The audio signal SS is output and the directivity of the entire sound collection device is made to follow the direction of the sound source (in this example, the speaker's mouth). In the sound collecting device according to the present embodiment, for the convenience of a subsequent device (not shown) that receives and processes the final digital audio signal SS, a signal (S / N ratio) of the digital audio signal SS ( Hereinafter, the signal is generated and output). Hereinafter, the circuit configuration of the sound collection device for obtaining the digital audio signal SS and the S / N ratio signal will be described.

  In FIG. 1, an A / D converter 12-k (k = 1 to m) samples an analog audio signal output from a microphone 11-k (k = 1 to m) at a constant sampling period, and samples values. Is converted into a digital audio signal Sk (k = 1 to m). The digital audio signals Sk (k = 1 to m) are respectively input to the extraction unit 20-k (k = 1 to m) and also input to the output signal synthesis unit 30.

  The extraction unit 20-k (k = 1 to m) is a voice intensity signal Es-k (k = 1 to m) indicating the intensity of the voice component from each of the digital audio signals Sk (k = 1 to m) and This is a circuit for extracting a noise intensity signal En-k (k = 1 to m) indicating the intensity of the noise component. In the present embodiment, which of the digital audio signals Sk (k = 1 to m) is output as the final digital audio signal SS by the level comparison of the sound intensity signal Es-k (k = 1 to m). Make a decision. In this embodiment, the S / N ratio signal is calculated from the voice intensity signal Es-k (k = 1 to m) and the noise intensity signal En-k (k = 1 to m).

  FIG. 4 is a block diagram showing the configuration of each of the extraction units 20-k (k = 1 to m). In FIG. 4, a BPF (band pass filter; band pass filter) 21 has a pass band of 300 to 3000 Hz, for example, and passes an audio frequency component included in the digital audio signal Sk. The output signal of the BPF 21 indicates the intensity of the audio component in the digital audio signal Sk, but its value changes rapidly and frequently. Therefore, if the output signal of the BPF 21 is output as it is as the audio intensity signal Es-k, the digital audio signal Sk selected as the digital audio signal SS is frequently switched, and the operation becomes unstable. Therefore, an envelope generator 22 is provided at the subsequent stage of the BPF 21. The envelope generator 22 outputs an audio intensity signal Es-k indicating an envelope (envelope) in which an abrupt change in the output signal of the BPF 21 is relaxed. Specifically, the envelope generation unit 22 includes an effective value calculation circuit and an LPF (low pass filter). Here, the effective value calculation circuit divides the output signal of the BPF 21 into frames made up of a predetermined number of samples, and calculates an effective value that is the mean square of each sample for each frame. The LPF removes an abrupt change in the effective value obtained for each frame, and outputs an audio intensity signal Es-k indicating an envelope of the effective value.

  A BEF (band elimination filter; band elimination filter) 23 has a cut-off band of, for example, 300 to 3000 Hz, and allows a band component other than the cut-off band included in the digital audio signal Sk to pass therethrough. The output signal of the BEF 23 indicates the intensity of the noise component in the digital audio signal Sk, but its value changes rapidly and frequently. Therefore, if the output signal of the BEF 23 is output as it is as the noise intensity signal En-k, it is calculated from the voice intensity signal Es-k (k = 1 to m) and the noise intensity signal En-k (k = 1 to m). The S / N ratio signal becomes unstable. Therefore, an envelope generation unit 24 similar to the envelope generation unit 22 is provided at the subsequent stage of the BEF 23. The envelope generator 24 outputs a noise intensity signal En-k indicating an envelope in which an abrupt change in the output signal of the BEF 23 is mitigated.

  FIG. 5 is a block diagram illustrating another configuration example of the extraction unit 20-k (k = 1 to m). In this example, the BEF 23 in FIG. The subtracter 25 subtracts the output signal of the BPF 21 from the digital audio signal Sk and supplies it to the envelope generation unit 24. Also in this configuration, the sound intensity signal Es-k and the noise intensity signal En-k similar to those shown in FIG. 4 are output from the envelope generators 22 and 24, respectively.

  In FIG. 1, the output signal synthesis unit 30 selects one of the digital audio signals Sk (k = 1 to m) and outputs it as the digital audio signal SS, or the digital audio signal Sk (k = 1 to m) is a circuit that performs crossfading on two signals and outputs a digital audio signal SS. The output signal synthesizer 30 multiplies the digital audio signal Sk (k = 1 to m) by a coefficient ak (k = 1 to m) and outputs the multiplier 31-k (k = 1 to m). ), An adder 32 that adds the output signals of the multipliers 31-k (k = 1 to m) and outputs them as a digital audio signal SS, and a synthesis control that controls the coefficients ak (k = 1 to m) Part 33.

  The switching control unit 40 is a circuit that monitors the voice intensity signal Es-k (k = 1 to m) and outputs the selection signals Mnew and Mold and the crossfade signal CF based on the monitoring result. Here, the selection signal Mnew is a signal indicating the index k of the most suitable digital audio signal SS among the digital audio signals Sk (k = 1 to m). The selection signal Mold is a signal indicating a value immediately before the selection signal Mnew is changed to the current value. In principle, the switching control unit 40 performs a switching control process for verifying the selection signals Mnew and Mold and performing necessary updates every time the periodic verification pulse Pc is given. In this switching control process, the level of the voice strength signal Es-k (k = 1 to m) is compared except during the period in which the crossfade signal CF is “1”, and roughly speaking, the voice strength signal of the maximum level. The selection signal Mnew is updated so as to indicate the index k of Es-k. In the switching control process, when the content of the selection signal Mnew is changed, the selection signal Mold is updated with the content of the selection signal Mnew before the change. Various modes can be considered for the switching control process, but the details will be clarified in the description of the operation of the present embodiment in order to avoid duplication of explanation.

  The synthesis control unit 33 in the output signal synthesis unit 30 monitors the selection signal Mnew updated in this way, and the digital audio signal Sk having the index k specified by the selection signal Mnew is the final digital audio. The value of the coefficient ak (k = 1 to m) is controlled so as to be output as the signal SS. Specifically, the composition control unit 33 sets the coefficient a-k having the index k specified by the selection signal Mnew to “1” and the other coefficients to “0”.

  Here, since the m microphones 11-k (k = 1 to m) in the present embodiment have the maximum sensitivity axes whose directions are different from each other, the digital audio signal Sk (k = 1) is generally used. There is a level difference between ~ m). For this reason, when the content of the selection signal Mnew changes, if the digital signal Sk that is the digital audio signal SS is immediately switched accordingly, an unnatural discontinuity occurs in the digital audio signal SS. Therefore, in the present embodiment, the switching control unit 40 causes the output signal synthesis unit 30 to perform a crossfade over a predetermined period when changing the contents of the selection signals Mnew and Mold.

  Specifically, when the contents of the selection signals Mnew and Mold are changed, the switching control unit 40 raises the crossfade signal CF from “0” to “1” at that time, and outputs the crossfade signal CF. After setting it to “1” for a predetermined period, it returns to “0” again. The synthesis control unit 33 in the output signal synthesis unit 30 changes the coefficient (for example, a-newk) for which the index is designated by the selection signal Mnew from “0” to “1” during the period when the crossfade signal CF is “1”. The coefficient (for example, a-oldk) whose index is designated by the selection signal Mold is continuously changed from “1” to “0”. In this way, since the old and new digital audio signals Sk are cross-faded, an unnatural discontinuity does not occur in the digital audio signal SS.

The S / N ratio signal generation unit 50 selects a speech intensity signal Es-k (k = 1 to m) having an index k specified by the selection signal Mnew as an S component, and a noise intensity signal En−. This is a circuit that selects the highest intensity among k (k = 1 to m) as an N component, and outputs the result of dividing the signal level of the S component by the signal level of the N component as an S / N ratio signal. The output unit 60 is a circuit that outputs the final digital audio signal SS obtained from the output signal synthesis unit 30 and the S / N ratio signal obtained from the S / N ratio signal generation unit 50.
The above is the configuration of the present embodiment.

<Operation of Embodiment>
(1) Overall Operation Next, the operation of this embodiment will be described. FIG. 6 is a time chart showing an operation example of the present embodiment. This operation example is an operation example of a sound collection device having three microphones 11-k (k = 1 to 3) as illustrated in FIG. 2 or FIG. As in this operation example, in this embodiment, every time the periodic verification pulse Pc is generated, the switching control unit 40 executes the switching control process, and the voice intensity signal Es-k (k = 1 to 3) Level comparison is performed.

  In this operation example, the speaker's mouth, which is a sound source, moves from the front of the sound collection device to the right side. When the sound source is in front of the sound collection device, the level of the sound intensity signal Es-2 is the maximum among the sound intensity signals Es-k (k = 1 to 3). Therefore, in the switching control process that is repeatedly executed, the selection signal Mnew is set to “2”, which is an index that designates the digital audio signal S-2 obtained from the central microphone 11-2.

  However, as the sound source moves from the center of the sound collecting device to the right side, the level of the sound intensity signal Es-2 gradually decreases and the level of the sound intensity signal Es-3 gradually increases. In the operation example, when the switching control process is executed at time t1, the magnitude relationship between the levels of the sound intensity signals Es-2 and Es-3 is reversed, so the selection signal Mnew is set to “3”. The selection signal Mold is set to “2”. After this point, the crossfade signal CF is set to “1” for a predetermined period. While the crossfade signal CF is “1”, the switching control process is not executed even if the verification pulse Pc is generated.

  The output signal synthesizer 30 takes a period in which the crossfade signal CF is “1” and reduces the coefficient a-2 to be multiplied by the digital audio signal S-2 from “1” to “0”; An operation of increasing the coefficient a-3 multiplied by the digital audio signal S-3 from “0” to “1” is performed. As a result, the digital audio signal SS finally output naturally shifts from the digital audio signal S-2 to the digital audio signal S-3.

  As described above, the S / N ratio signal generation unit 50 calculates the S / N ratio signal from the voice intensity signal Es-k (k = 1 to 3) and the noise intensity signal En-k (k = 1 to 3). Is done. In the case of this operation example, the period during which the selection signal Mnew is “2” is the maximum of the audio intensity signal Es-2 corresponding to the index “2” and the noise intensity signal En-k (k = 1 to 3). An S / N ratio signal is calculated from the level. Further, during the period when the selection signal Mnew is “3”, the voice intensity signal Es-3 corresponding to the index “3” and the noise intensity signal En-k (k = 1 to 3) having the maximum level are selected. To calculate the S / N ratio signal. The output unit 60 outputs the digital audio signal SS and the S / N ratio signal obtained in this way to a subsequent device.

(2) Various aspects of the switching control process The switching control process executed by the switching control unit 40 in the present embodiment is sufficient if it has a response level enough to follow the movement of the speaker's mouth position. If the switching control process responds too sensitively to changes in the sound intensity signal Es-k (k = 1 to m), the digital audio signal Sk that is the final digital audio signal SS is frequently switched, and the final The digital audio signal SS becomes unnatural for hearing. Hereinafter, aspects of the switching control process for preventing such inconvenience will be described by taking m = 3 as an example.

a. First Aspect In this aspect, a threshold th that is a boundary between a voice level and a background noise level is used, and only those having a level equal to or higher than the threshold th among voice intensity signals Es-k (k = 1 to 3). Are used as materials for determination in the selection of the digital audio signal Sk. FIGS. 7A and 7B show an execution example of the switching control process in this mode. In each example shown in FIGS. 7A and 7B, the verification pulse Pc is generated at time t11 and time t12, and the switching control process is executed. In these drawings, in order to prevent the illustration from being complicated, the sound intensity signals Es-k (k = 1 to 3) generated at times t11 and t12 are shown side by side in the horizontal direction.

  In the example shown in FIG. 7A, in the switching control process at time t11, since the level of the voice strength signal Es-2 is the maximum and is equal to or higher than the threshold th, the selection signal Mnew is “2”. The digital audio signal S-2 is selected as the digital audio signal SS. In the switching control process at time t12, since the level of the sound intensity signal Es-1 is the maximum and is equal to or higher than the threshold th, the selection signal Mnew is set to “1”, and the digital audio signal S-1 is converted to the digital audio signal. Selected as SS.

  However, in the example shown in FIG. 7B, in the switching control process at time t12, the level of any voice intensity signal Es-k (k = 1 to 3) has not reached the threshold th, and the digital audio signal S There is no voice intensity signal Es-k that serves as a reference for selecting -k. For this reason, in the switching control process at time t12, the selection signal Mnew = “2” obtained in the switching control process at time t11 is maintained.

  According to this aspect, even if the magnitude relationship of the level of the voice intensity signal Es-k (k = 1 to 3) changes within the range of the background noise level, such a change is ignored, and the current selection signal Mnew is maintained. Therefore, it is possible to prevent the digital audio signal Sk that becomes the digital audio signal SS from being frequently switched when the level of collected sound is low.

b. Second Mode Also in this mode, as in the first mode, only the voice intensity signal Es-k (k = 1 to 3) having a level equal to or higher than the threshold th is used as a material for determination in the switching control process. Further, in this aspect, in order to select a digital audio signal Sk as the digital audio signal SS in the switching control process, the level of the audio intensity signal Es-k corresponding to the digital audio signal Sk is set. It is not sufficient that the maximum is the voice intensity signal Es-k (k = 1 to 3). In order for the digital audio signal Sk to be selected as the digital audio signal SS, the level of the voice strength signal Es-k corresponding to the digital audio signal SS is the level of the voice strength signal that has the maximum level in the previous switching control process. It must be exceeded.

  FIG. 8 shows an execution example of the switching control process in this mode. In this example, in the switching control process at time t22, the level of the sound intensity signal Es-2 is the maximum and is equal to or greater than the threshold th. Further, the level of the voice strength signal Es-2 is higher by a positive value iVGC than the level of the voice strength signal Es-1 that has the maximum level in the previous switching control process (switching control process at time t21). Therefore, in the switching control process at time t22, the selection signal Mnew is set to “2”, and the digital audio signal S-2 is selected as the digital audio signal SS.

  Although illustration is omitted, if the level of the voice strength signal Es-2 that is maximum in the switching control process at time t22 is equal to or lower than the level of the voice strength signal Es-1 at the time of switching control process at time t21, The digital audio signal S-2 is not selected as the digital audio signal SS.

  According to this aspect, the selection signal Mnew is switched only when there is a clear change in the magnitude relationship of the voice intensity signal Es-k (k = 1 to 3), so that the digital audio signal SS becomes the digital audio signal SS. It is possible to prevent the audio signal S-k from being frequently switched.

c. Third Aspect In this aspect, the stability of the selection signal Mnew in the second aspect is further enhanced. Also in this aspect, as in the first and second aspects, only the sound intensity signal Es-k (k = 1 to 3) having a level equal to or higher than the threshold th is used as a material for determination in the switching control process. In this aspect, in order to select the digital audio signal Sk corresponding to a certain sound intensity signal Es-k as the digital audio signal SS in the switching control process, it is necessary to satisfy the following condition. .
Condition 1: The level of the voice strength signal Es-k is the maximum among the voice strength signals Es-k (k = 1 to 3).
Condition 2: Increment iVGC of the voice strength signal Es-k with respect to the maximum level voice strength signal in the previous switching control processing and the increment of the voice strength signal Es-k with respect to the maximum level voice strength signal in the previous switching control processing. iVGCR> iVGC when compared with iVGCR.

  FIG. 9 shows an execution example of the switching control process in this mode. In this example, in the switching control process at time t33, the level of the sound intensity signal Es-2 is the maximum and is equal to or greater than the threshold th. Further, the level of the voice strength signal Es-2 at the time of the switching control process at time t33 is higher than the level of the voice strength signal Es-2 that has the maximum level in the previous switching control process (switching control process at time t32). Is also increased by a positive value iVGC. Furthermore, the level of the voice strength signal Es-2 at the time of the switching control process at time t33 is higher than the level of the voice strength signal Es-1 that has the maximum level in the previous switching control process (switching control process at time t31). Increased by a positive value iVGCR. And iVGCR> iVGC. Therefore, in the switching control process at time t33, the selection signal Mnew is set to “2”, and the digital audio signal S-2 is selected as the digital audio signal SS.

  Although illustration is omitted, if the condition of iVGCR> iVGC is not satisfied even if the level of the audio intensity signal Es-2 is maximum in the switching control process at time t33, the digital audio signal S-2 is digital. It is not selected as the audio signal SS.

  According to this aspect, even if there is a temporary change in the magnitude relationship of the voice strength signal Es-k (k = 1 to 3), it is ignored, and a certain voice strength signal Es-k is at the maximum level, and Only when it is clearly recognized that there is an increasing tendency, the corresponding digital audio signal Sk is selected as the final digital audio signal SS. Therefore, it is possible to prevent the digital audio signal Sk as the digital audio signal SS from being frequently switched.

(3) Modes of Output of Digital Audio Signal SS and S / N Ratio Signal There are various modes for the output of the digital audio signal SS and S / N ratio signal in the output unit 60.

  In an aspect, the output unit 60 outputs a set of an S / N ratio signal and a digital audio signal SS for each sample as illustrated in FIG. In this case, each sample of the S / N ratio signal and the digital audio signal may be a separate word, but for example, the words having the S / N ratio signal as the upper bit string and the digital audio signal SS as the lower bit string are sequentially arranged. The output unit 60 may be configured to output. According to this aspect, the subsequent apparatus that receives the output signal of the sound collecting apparatus has an advantage that a digital audio signal and an S / N ratio signal corresponding to the digital audio signal can be obtained at an arbitrary timing.

  In another aspect, as illustrated in FIG. 11, the output unit 60 divides the digital audio signal SS into frames each including a predetermined number of samples, and a representative S / N ratio signal (for example, the frame) in the frame unit. Average value) and a predetermined number of samples of the digital audio signal SS belonging to the frame. According to this aspect, there is an advantage that the data amount as a whole can be reduced.

<Effect of embodiment>
As described above, in this embodiment, even in a situation where the position of the sound source changes, the digital audio signal Sk having the maximum sound component intensity is selected and output as the final digital audio signal SS. Therefore, a digital audio signal can always be acquired with the maximum sound receiving sensitivity regardless of the change in the position of the sound source. Further, in the present embodiment, when switching the digital audio signal to be output as the final digital audio signal SS, a certain time is required and a crossfade is performed between the old and new digital audio signals. There is an advantage that an unnatural discontinuity does not occur in the audio signal SS.

<Other embodiments>
Although one embodiment of the present invention has been described above, other embodiments are possible for the present invention. For example, in the above-described embodiment, the digital audio signal Sk that is the final digital audio signal SS is selected based on the audio intensity signal Es-k (k = 1 to m). Each of k (k = 1 to m) is divided by each of noise intensity signals En-k (k = 1 to m) to generate an S / N ratio signal S / Nk (k = 1 to m). The digital audio signal Sk corresponding to the S / N ratio signal S / Nk having the highest level may be selected as the final digital audio signal SS. According to this aspect, for example, when noise occurs in a specific direction, the level of the noise intensity signal generated based on the output signal of the microphone that picks up the noise increases, and the digital audio obtained from the microphone is increased. It can be avoided that the signal is selected as the final digital audio signal SS. Therefore, sound can be collected with a high S / N ratio even in a situation where local noise suddenly occurs.

It is a block diagram which shows the structure of the sound collection device which is one Embodiment of this invention. It is a figure which shows the example of mounting of the microphone in the embodiment. It is a figure which shows the other mounting example of the microphone in the embodiment. It is a block diagram which shows the structural example of the extraction part in the embodiment. It is a block diagram which shows the other structural example of the extraction part in the embodiment. It is a time chart which shows operation | movement of the embodiment. It is a time chart which shows the 1st aspect of the switching control process in the embodiment. It is a time chart which shows the 2nd aspect of the switching control process in the embodiment. It is a time chart which shows the 3rd aspect of the switching control process in the embodiment. It is a figure which shows the aspect of the output of the S / N ratio signal and digital audio signal of the output part in the embodiment. It is a figure which shows the other aspect of the output of the S / N ratio signal and digital audio signal of the output part in the embodiment.

Explanation of symbols

11-k (k = 1 to m)... Microphone, 12-k (k = 1 to m)... A / D converter, 20-k (k = 1 to m). Output signal synthesis unit, 31-k (k = 1 to m)... Multiplier, 32... Adder, 33... Synthesis control unit, 40 ... switching control unit, 50 ... S / N ratio signal generation unit , 60 ... Output section.

Claims (9)

Multiple microphones that pick up sound from the outside world and output electrical signals;
Output signal synthesis means for synthesizing and outputting an audio signal to be output from each output signal of the plurality of microphones;
Extraction means for extracting at least a sound component from each output signal of the plurality of microphones and outputting a signal indicating the intensity or S / N ratio of the sound component of each signal;
Based on the output signal of the extracting means, the output signal synthesizing means is arranged so that a signal having a high intensity of a sound component or a high S / N ratio among the output signals of the plurality of microphones is output by the output signal synthesizing means. And a switching control means for executing a switching control process for controlling the sound collecting device.   The sound collecting apparatus according to claim 1, wherein the switching control unit periodically repeats the switching control process.   The extraction means outputs a plurality of sound intensity signals each indicating the intensity of the sound component of each output signal of the plurality of microphones, and the switching control means performs the switching control processing based on the plurality of sound intensity signals. The sound collecting device according to claim 2, wherein the sound collecting device is executed.   In the switching control process periodically repeated, the switching control means recognizes that the intensity of the sound component of the output signal of the microphone recognized as the maximum in the current switching control process is the maximum in the previous switching control process. The output signal of the microphone recognized as having the maximum intensity of the sound component in the current switching control process is output by the output signal synthesizing means when the intensity is higher than the intensity of the sound component of the output signal of the selected microphone. 4. The sound collecting device according to claim 3, wherein the output signal synthesizing means is controlled.   The switching control means was recognized to be the maximum in the current switching control process with respect to the intensity of the sound component of the output signal of the microphone, which was recognized as the maximum in the previous switching control process, in the switching control process periodically repeated. In the current switching control process for the first increase, which is the increase in the intensity of the audio component of the output signal of the microphone, and the intensity of the audio component of the output signal of the microphone recognized as the maximum in the previous switching control process When the second increase is compared with the second increase, which is the increase in the intensity of the audio component of the recognized microphone output signal, and the second increase is greater than the first increase, the current switching In the control process, the output signal of the microphone recognized as having the maximum intensity of the voice component is output by the output signal synthesizing means. Pickup device according to Claim 3, wherein the controller controls the output signal combining means.   6. The sound collecting device according to claim 2, wherein the switching control unit executes the switching control process using only a sound intensity signal having a predetermined threshold value or more as a determination material.   The output signal synthesizing means takes a predetermined time when switching the output signal from the old one to the new one among the output signals of the plurality of microphones, and the signal after switching from the signal before switching to the signal after switching. The sound collecting device according to any one of claims 1 to 6, wherein the sound collecting device is cross-faded.   4. The sound collection device according to claim 3, wherein the extraction unit outputs an envelope of an effective value of a signal in a sound frequency band included in output signals of the plurality of microphones as the sound intensity signal.   The sound collecting device according to any one of claims 1 to 8, wherein the plurality of microphones are fixed with different directions in which the maximum sound receiving sensitivity can be obtained.

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