JPH1118191A - Sound pickup method and device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a sound collecting method and an apparatus for removing the influence of received voice radiated from a speaker when the sound collecting device is applied to a communication conference. SOLUTION: A sound source existence area detecting section 32 detects a target speaker area from an output signal of a directivity scanning section 31 which scans the directivity of a microphone array 21. The directivity of the microphone array 21 is controlled so that the receiving speaker 24, the area near the receiving speaker, or the specified specific region is excluded from the detection of the sound source existence region by the sound source existence region detection limiting unit 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound pickup method and a sound pickup apparatus for processing a signal output from a microphone array composed of a plurality of microphones to pick up sound. Method and apparatus for detecting received voice when applied to telecommunications conferences in Japan, and aiming at the directivity of the microphone array in the direction of the target voice accurately by removing the effect of the received voice radiated from the receiving speaker The present invention relates to a sound collecting method and device capable of picking up sound.

[0002]

2. Description of the Related Art In recent years, with the advancement of multimedia technology, it has become possible to conduct a teleconference such as a video conference using a microphone and a speaker in a voice call mode.
In such a case, there is a demand for a sound collecting device capable of making a natural call without being conscious of the microphone and installing only a purpose such as voice without installing microphones for the number of speakers on the desk of the communication conference. .

[0003] As an example of such a sound pickup device, there is a sound pickup device in which a plurality of microphones (microphone arrays) are installed and their outputs are subjected to signal processing to extract a target sound. Signal processing methods for suppressing noise and extracting a target sound using such a microphone array include a delay-and-sum method,
Many are known such as MNOR (for example, Oga, Yamazaki,
Kanada, "Acoustic systems and digital processing," IEICE, 1995. pp. 173-197) For example, in the delay-and-sum method, a target sound is extracted as follows.

FIG. 6 is a diagram for explaining the principle of target sound extraction by the delay-and-sum method. In FIG. 6, 1 is a sound collection unit (microphone array), 2 ₁ , 2 ₂ ,..., 2 _M is a microphone (M is the number of microphones), 3 ₁ , 3 ₂ ,.
.., 3 _M is a delay unit, 4 is an adder, 5 is an output signal, 6 is a noise suppression unit, d is a microphone interval, and s (t) is a sound pickup unit 1
(T represents time), θ is a sound wave s (t)
Is the arrival angle at which the sound arrives at the sound pickup unit 1, and τ is the time difference (delay time) at which the sound wave reaches each microphone.

The microphones 2 ₁ , 2 ₂ ,...
2 _M are arranged linearly at equal intervals d, and the sound wave s (t) arrives at an angle θ from a distance to the microphones arranged linearly. The distance the sound wave reaching the microphone 2 ₁ propagates before reaching the microphone 2 ₂ is represented by dsinθ from the arrival angle θ microphone spacing d. Similarly, the i-th microphone 2 _i (i =
2,..., M)
(I-1) It is represented by dsinθ. Accordingly, the microphone _{2 i (i = 2, ···} , M) is a delay time tau _i to reach, when the reference microphone 2 _1, by dividing the propagation distance at the speed of sound c, the following equation (1 ).

[0006]

(Equation 1) Here, an output signal from each microphone 2 _i (i = 1,..., M) is represented by X _i (t), which is a sound wave s.
Since (t) is delayed by τ _i , the following equation (2) is obtained.

[0007]

(Equation 2) Here, if the delay amount D _i of the delay unit 3 _i (i = 1, 2,..., M) is appropriately set, only the sound wave arriving from the θ direction can be emphasized and output to the output signal 5. Shown in

The delay amount D _i of the delay unit 3 _i (i = 1, 2,..., M) is set as in the following equation (3).

[0009]

(Equation 3) _Do is a fixed delay amount added to prevent a decrease in accuracy when realizing delay characteristics with a digital filter when the value of τ _i is too small.

At this time, the delay units 3 _i (i = 1, 2,...)
, M) is obtained by adding the signal of equation (2) to the delay D of equation (3).
_{Since i} occurs, the following equation (4) is obtained.

[0011]

(Equation 4) That is, regardless of the microphone number i, s (t)
Is the same signal delayed by D ₀ .

If the signals are added by the adder 4 after the phases are aligned in this way, the sound waves arriving from the θ direction are emphasized by the added amount. On the other hand, sound waves and theta directions coming from another theta _N direction, since it is sound receiving with different delay times tau _N and tau _i, the phase is not aligned in the delay amount of a compound of formula (3), by the adder 4 Addition of the signals does not add emphasis.

As described above, in the delay-and-sum method, a sound wave arriving from a target direction θ is emphasized, and noise arriving from another direction θ _N is relatively suppressed.

At this time, if the target direction θ is scanned and the output signal of the microphone array 1 is monitored, the output signal becomes large when θ is directed to the target speaker, so that the direction of the target speaker is searched. be able to. Then, the target sound is obtained by aligning and adding the phases according to equation (4) so as to emphasize the sound wave from the direction θ of the target speaker, that is, directing the directivity of the microphone array 1 in the direction θ. Sound can be collected with a high SN ratio.

Here, for convenience of explanation, a plurality of microphones are described as being arranged on a straight line at equal intervals d. However, the microphones can be arranged at irregular intervals, and the arrangement shape is two-dimensional. They may be arranged in three dimensions.

When the sound source S, which is a point sound source, is located at a relatively short distance from the microphone array 1 as shown in FIG.
_1, 3 _2,..., 3 gain 7 ₁ to the subsequent stage of the _M, 7 _2, ·
It is important to improve the sound pickup S / N ratio by providing..., 7 _M and applying an appropriate load to this gain. There is a way of applying the load as represented by the following formulas (5), (6), and (7) (Nomura, Kaneda, Kojima “Near-field microphone array”, Journal of the Acoustical Society of Japan, 53 Vol. 2 (199
7), p. 110-116).

[0017]

(Equation 5)

[0018]

(Equation 6)

[0019]

(Equation 7) Here, r ₁ , r ₂ ,..., R _M are the distances from the sound source S to the microphones 2 ₁ , 2 ₂ ,..., 2 _M , and r _C is the critical distance in the room, that is, the direct sound power of the sound source. This is the distance at which the reverberation sound power becomes equal. For a room volume V [m3] and a room reverberation time T [sec], r _C = √ (0.0032 V /
T) (H.Kuttruff, “RoomAcoustics (Thir
d Edition) ", Elsevier Applied Science, pp. 100-132
(1991)). At this time, the microphone array 1 has the highest sensitivity with respect to the "point" of the position of the sound source S, so that a "focus" of the sensitivity is formed. At this time, the distance r _i (i = 1, 2,...) To each microphone
·, M) delay units 3 _1, 3 ₂ against, · · ·, 3 _M of delay _{D 0 -r i / c (c} : sound velocity) and by changing the above-mentioned gain g ₀ i.e. a scanning focus sensitivity If the output of the array is monitored, the output of the array is increased when the sensitivity is focused on the point where the target speaker is present, so that the position of the target speaker can be found.

In this way, by finding the target speaker's existence area as the direction or position, and directing the array directivity to the existence area, the target sound can be picked up with a high sound pickup SN ratio.

[0021]

An attempt is made to apply the microphone array 1 to a communication conference such as a video conference. The advantage of using the microphone array 1 as a sound pickup unit or the like in a communication conference is that the microphone array 1 can be installed at a position away from the speaker with a high sound collection S / N ratio, so that a plurality of microphones are installed on a desk. There are advantages such as no necessity, microphone awareness, and natural communication.

FIG. 8 shows an example of a communication conference apparatus using the microphone array 1 as a sound pickup unit. In this figure, 10A, 1
0B denotes a communication conference room, 11A and 11B denote microphone arrays 12A and 12B, a microphone array main unit, 13 denotes a communication line, and 14A and 14B denote receiving speakers. The target voice uttered in the conference room 10A is the microphone array 1
After the sound is picked up by 1A and subjected to processing for emphasizing the target sound by the microphone array main unit 12A, the sound is transmitted to the communication conference room 10B, which is the communication destination, via the communication line 13, and is emitted from the speaker 14B as the reception sound Is done. The flow of the signal for the target voice uttered in the communication conference room 10B is the same as the flow described above. Microphone array main unit 12
A and 12B correspond to the microphone array 11 as described above.
The directionality of the target speaker is detected by scanning the directivity of A and 11B, and the microphone arrays 11A and 11B operate so that the directionality of the target speaker is directed to the presence area of the target speaker. To work.

As described above, the microphone array 11A, 1
1B has an effect of detecting the target speaker's existence area, directing the directivity of the microphone arrays 11A and 11B to this existence area, and collecting the target sound at a high SN ratio. However, the receiving voice from the communication destination is
When radiated from A or 14B, the receiving speaker 14A or 14B is often erroneously detected as a target speaker, and the directivity of the microphone arrays 11A and 11B is turned to the direction of the receiving speaker 14A or 14B. Was. Further, at this time, the sound radiated from the receiving speaker 14A or 14B is transmitted to the microphone array 1
It has also been found that the sound is picked up by 4A or 14B and returned to the communication conference room 10A or 10B where the speaker is again present, and is perceived as an echo, or the quality of speech deteriorates due to howling or the like.

[0024]

In order to solve the above problem, the present invention has the following arrangement. First, a directivity control unit is provided to prevent directivity of the microphone array from being directed to the position of the receiving speaker. However, this is insufficient in practical use. That is, the first reflected sound for the sound radiated by the receiving speaker is generated from the floor / wall in the area near the receiving speaker. Generally, since the first reflected sound has high energy, the microphone array may perform erroneous detection due to the influence of the reflected sound. To prevent this,
A directivity control unit is provided for preventing the directivity of the microphone array from being directed not only to the position of the receiving speaker but also to a region near the receiving speaker including the receiving speaker. The area near the receiving speaker is an area having a radius of about 0.5 to 2 m centered on the receiving speaker. Determined depending on conditions. However, it is desirable to increase the size as long as it does not overlap with the area where the target speaker exists.

The most basic method or means of directivity control is a method of excluding the area Fsp where the receiving speaker exists or the area Fn near the receiving speaker from the directivity scanning range for detecting the target speaker. In addition, when the sound pressure of a specific area in the room other than the area near the receiving speaker is increased due to the reflection of the received voice radiated from the receiving speaker in the room, or the noise coming from the air conditioning or the window or wall of the room, etc. The specific area is also set so as to be excluded from the directivity scanning range together with the receiving speaker or the area near the receiving speaker.

In order to realize the same purpose,
The following means can also be applied. When detecting the target speaker's presence area by directing the directivity to the area where the average power of the microphone array output is high, the power for each area to calculate the power for each area when scanning the directivity A calculation unit is provided to calculate the power for each area excluding the receiving speaker, the area near the receiving speaker, and the designated specific area, and detect a high-power area as a sound source area from the power calculated by the area-specific power calculation unit. can do. In this way, it is possible to avoid a problem that the receiving speaker, the area near the receiving speaker, or the specified specific area is erroneously detected as the target speaker's existing area.

Further, in order to realize the same purpose, the following means can be applied. That is, from the output of each area power calculation unit that calculates the power for each area when the directivity is main-scanned, the high power is selected from the power for each area except the receiving speaker, the area near the receiving speaker, or the specified specific area. The region may be detected as the sound source region.

The method described above for preventing the directivity of the microphone array from being directed to the receiving speaker, the area near the receiving speaker, or a specific area that has been set, is based on collecting the uttered voice of the speaker and in the same room where the speaker is located. The present invention can also be applied to in-field loudspeakers in which the loudspeakers are used. For example, when a listener asks a question in a lecture meeting in a relatively large place, the listener's question is loudspeaked in a hall using a speaker or the like in order to make the content of the question easier to hear. It is conceivable to direct the directivity to the listener using the above-mentioned microphone array when collecting the listener's question, but if the energy of the sound wave radiated from the loudspeaker is large, the microphone array will ask the question. Means of controlling the directivity except for a speaker for loudspeaker, a region near the loudspeaker for loudspeaker, or a specified specific region other than the listener who is listening.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The sound pickup method and apparatus according to the present invention prevent radiation of directivity of a microphone array to a receiving speaker, a region near the receiving speaker, or a specified specific region, thereby radiating from the receiving speaker. This is configured to prevent the influence of the received voice to be received and to prevent the microphone array from being erroneously directed to the receiving speaker, the area near the receiving voice, or the designated specific area where the target voice does not exist.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In the figure, reference numeral 20 denotes a communication conference device, which includes a microphone array 21, a microphone array main device 22, a transmission line 23-2 serving as transmission means, a reception line 23-1 serving as reception means, a reception speaker 24, and a directivity control unit. 30.

In operation, the signal picked up by the microphone array 21 is subjected to signal processing by the microphone array main unit 22, and the directivity of the microphone array 21 is directed to the area where the target speaker is present. High SN
The sound is collected at the ratio, and the target voice is transmitted to the communication destination through the transmission line 23-2. A reception signal received from a communication destination via the reception line 23-1 is radiated by the reception speaker 24 as reception voice. At this time, the microphone array 2 is mistakenly placed in the receiving speaker 24 where the target speaker is not speaking or in the vicinity of the receiving speaker 24 or in the specified specific region.
In order to prevent the directivity of the microphone array 21 from being directed, the directivity control unit 30 controls the signal processing of the microphone array main device 22 and controls the directivity of the microphone array 21.

FIG. 2 shows a second embodiment of the present invention. In the figure, 31 is a directional scanning unit, 32 is a sound source existence area detection unit, and 33 is a sound source existence area detection limiting unit. The directivity control unit 30 is formed as described above. The same reference numerals as those in FIG. 1 denote the same parts.

Next, the operation will be described. The target speaker area is detected by the sound source existence area detection section 32 from the output signal of the directivity scanning section 31 that scans the directivity of the microphone array 21. The receiving speaker 24, the area near the receiving speaker, or the specified specific region is excluded from the detection of the sound source existence region by the sound source existence region detection limiting unit 33.

FIG. 3 shows a third embodiment of the present invention. This embodiment is similar to the sound source existence region detection unit 3 of the second embodiment shown in FIG.
2 is composed of an area-specific power calculation section 321 and an area-specific power maximum area detection section 322, and the rest is the same as FIG.

Next, the operation will be described. The power of the output signal of the directivity scanning unit 31 is calculated by the region-specific power calculation unit 321, and the region where the power calculated by the region-specific power calculation unit 321 is maximum is detected by the region-specific power maximum region detection unit 322, Performs a sound source area detection unit.

FIG. 4 shows a fourth embodiment of the present invention. In this embodiment, a directional scanning limited output power calculation unit 323 for calculating the power of the output signal of the directional scanning unit 31 for each area other than the receiving speaker 24, the area near the receiving speaker, and the set specific area, and this directivity. Directional scanning limited output power maximum region detecting unit 3 for detecting a region where the power calculated by directional scanning limited output power calculating unit 323 is maximum
24 is an embodiment in which the sound source existence area detection unit 32 is configured from the H.24. Others are the same as FIG.

FIG. 5 shows a fifth embodiment of the present invention. This includes a directional scanning unit 31 that scans the directivity of the microphone array 21, a scanning limiting unit 34 that inhibits scanning of the receiving speaker 24, the area near the receiving speaker, or a designated area, and a directional scanning unit. A directional scanning limited output power calculating unit 35 for calculating the power of the output signal of the output unit 31 and a directional scanning limited output power maximum area detecting unit for detecting a region where the power calculated by the directional scanning limited output power calculating unit 35 is maximum. 36 is an embodiment in which the directivity control unit 30 is composed of the directivity control unit 36 and the control unit 36.

[0039]

As described above, in the sound pickup method according to the present invention, sound is picked up by using a microphone array composed of a plurality of microphones and a microphone array main unit that performs signal processing on an output signal of the microphone array. In the sound collection method, a reception signal from a communication destination is received, the reception signal is radiated from a reception speaker as a reception sound wave, and the directivity of the microphone array is changed to the reception speaker, the reception speaker vicinity area, or a specified specific area. Since the directivity of the microphone array is controlled so as not to face the microphone array, the directivity of the microphone array is not directed to the receiving speaker or its vicinity or a specified specific area.

Further, the sound pickup apparatus according to the present invention is provided with a directivity control unit for preventing directivity of the array from being directed to the receiving speaker, the area near the receiving speaker, or a specified specific area, so that the sound is radiated from the receiving speaker. In this way, it is possible to prevent an operation of erroneously turning the directivity of the microphone array to a receiving speaker where no target voice is present, a region near the receiving speaker, or a specified specific region.

Further, a directional scanning section for scanning the directivity of the microphone array, a sound source existence area detection limiting section for detecting an existence area of a target sound source from an output signal of the directional scanning section, the receiving speaker or the receiving section Since the directivity control unit is composed of a directivity limiting unit that prohibits directing the directivity of the microphone array to an area in the vicinity of the speaker or a specified specific area, an error may occur in the receiving speaker or its vicinity or the specified specific area. Thus, directing the directivity of the microphone array can be effectively prevented.

A directional scanning limited output power calculator for calculating the power of the output signal of the directional scanning unit, and a directional main scanning area in which the calculated power of the directional scanning limited output power calculator is maximized. Since the sound source area detecting section is constituted by the directional scanning limited output power maximum area detecting section to be detected, the sound source area can be detected from the power, and reliable operation is guaranteed.

Further, a directional scanning unit for scanning the directivity of the microphone array, and the power of the output signal of the directional scanning for the receiving speaker, a region near the receiving speaker, or a region other than a specified specific region. A directional scanning limited output power calculating section for calculating, and a directional scanning limited output power maximum area detecting section for detecting an area where the power calculated by the directional scanning output power calculating section is maximum. With this configuration, the calculation amount can be reduced because some regions specified in the power calculation stage are excluded.

Also, a directional scanning unit for scanning the directivity of the microphone array, a scan limiting unit for inhibiting the directivity scanning of the receiving speaker, a region near the receiving speaker, or a specified specific area, Directional scanning limited output power calculating section for calculating the power of the output signal of the directional scanning section, and a directional scanning limited output power maximum area for detecting an area where the power calculated by the directional scanning limited output power calculating section is maximum Since the directivity control unit is constituted by the detection unit, some areas specified in the stage of directivity scanning are removed, so that the amount of calculation can be further reduced.

As described above, according to the present invention, it is possible to prevent the sound radiated from the receiving speaker from being picked up by the microphone array, and the sound uttered by the speaker is transmitted again through the line. It is possible to prevent echoes returning to the room where the user is located, and also to prevent howling, thereby achieving an unprecedented excellent effect of preventing deterioration in speech quality due to these echoes and howling.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of a sound collection device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment of the sound collection device of the present invention.

FIG. 3 is a block diagram showing a configuration of a third embodiment of the sound collection device of the present invention.

FIG. 4 is a diagram showing a configuration of a fourth embodiment of the sound collection device of the present invention.

FIG. 5 is a diagram showing a configuration of a fifth embodiment of the sound collection device of the present invention.

FIG. 6 is a diagram for explaining the principle of noise suppression sound collection by a conventional delay-and-sum method.

FIG. 7 is a diagram for explaining how to appropriately set the load of the gain at the subsequent stage of the delay unit and improve the sound collection S / N ratio when the sound source is located at a position close to the microphone array.

FIG. 8 is a block diagram illustrating a communication conference using a conventional microphone array.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Communication conference apparatus 21 Microphone array 22 Microphone array main unit 23-1 Receiving line 23-2 Transmitting line 24 Receiving speaker 30 Directivity control unit 31 Directional scanning unit 32 Sound source area detection unit 321 Power calculation unit for each area 322 Area Power maximum area detecting section 323 Directional scanning limited output power calculating section 324 Directional scanning limited output power maximum area detecting section 33 Sound source existence area detecting and limiting section 34 Scan limiting section 35 Directional scanning limited output power calculating section 36 Directional scanning limited Output power maximum area detector

Claims (6)

[Claims] 1. A sound collection method for collecting sound using a microphone array including a plurality of microphones and a microphone array main device that performs signal processing on an output signal of the microphone array, comprising: receiving a reception signal from a communication destination; The receiving signal is emitted from a receiving speaker as a receiving sound wave, and the directivity of the microphone array is controlled so as to prohibit the directivity of the microphone array from being directed to the receiving speaker, an area near the receiving speaker, or a specified specific area. A sound collection method. 2. A sound pickup device for picking up sound using a microphone array including a plurality of microphones and a microphone array main device that processes an output signal of the microphone array. Means, a receiving speaker for emitting a receiving signal from the receiving means as a receiving sound wave, and directivity control for inhibiting directivity of the microphone array from being directed to the receiving speaker, the area near the receiving speaker, or a specified specific area. And a sound collecting device. 3. The sound pickup device according to claim 2, wherein a directional scanning unit that scans the directivity of the microphone array, and an area where the target sound source exists is detected from an output signal of the directional scanning unit. The directivity control unit is constituted by a sound source existence region detection unit, and a sound source existence region detection limitation unit that prohibits directing the directivity of the microphone array to the reception speaker or a region near the reception speaker or a specified specific region. A sound pickup device characterized by the following. 4. The sound collection device according to claim 3, wherein the directional scanning output power calculator calculates the power of the output signal of the directional scanning unit, and the directional scanning output power calculator calculates the directional scanning output power. A sound-source-existing-area detection limiting section comprising a directional scanning output power maximum area detecting section for detecting a directional scanning area having the maximum power. 5. The sound pickup device according to claim 2, wherein a directional scanning unit that scans the directivity of the microphone array, and excludes the receiving speaker, an area near the receiving speaker, or a specified specific area. A directional scan limited output power calculator for calculating the power of the directional scan output signal for the area, and a directional scan for detecting an area where the power calculated by the directional scan limited output power calculator is maximum A sound collection device comprising the directivity control unit including a limited power output maximum area detection unit. 6. The sound pickup device according to claim 2, wherein the directional scanning unit scans the directivity of the microphone array, and the receiving speaker, a region in the vicinity of the receiving speaker or a specified specific region. A scan limiting unit that inhibits directional scanning, a directional scan limited output power calculator that calculates the power of the output signal of the directional scan unit, and a power calculated by the directional scan limited output power calculator is maximum. And a directional control section comprising a directional scanning limited output power maximum area detecting section for detecting an area to be detected.