WO2011099167A1 - Appareil de prise de son, appareil de communication portable et appareil de prise d'image - Google Patents

Appareil de prise de son, appareil de communication portable et appareil de prise d'image Download PDF

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Publication number
WO2011099167A1
WO2011099167A1 PCT/JP2010/052482 JP2010052482W WO2011099167A1 WO 2011099167 A1 WO2011099167 A1 WO 2011099167A1 JP 2010052482 W JP2010052482 W JP 2010052482W WO 2011099167 A1 WO2011099167 A1 WO 2011099167A1
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WIPO (PCT)
Prior art keywords
null
signal
pickup apparatus
microphones
sound
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PCT/JP2010/052482
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English (en)
Inventor
Toshimichi Tokuda
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Panasonic Corporation
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Priority to PCT/JP2010/052482 priority Critical patent/WO2011099167A1/fr
Publication of WO2011099167A1 publication Critical patent/WO2011099167A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
    • H04R1/406—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones

Definitions

  • the present invention relates to a sound pickup apparatus, which is incorporated in a portable communication terminal and a speech recognition terminal, capable of suppressing ambient sounds and clearly picking up the sound of a user, a portable communication apparatus and an image pickup apparatus provided with the sound pickup apparatus.
  • a portable communication terminal and a speech recognition terminal are used in an environment, in which much noise exists, such as outdoors, and a lowering in communication sound quality and speech recognition performance becomes problematic due to a mixture of noise into sound signals.
  • a sound pickup apparatus incorporated in such a terminal has a directivity by which a beam (a direction of especially high sensitivity) is formed in the direction in which a user utters. Therefore, noise that reaches the sound pickup apparatus from the surroundings of the user is suppressed, wherein the sound of the user is intensified, and improvement in the communication sound quality and speech recognition performance can be expected.
  • target signals such as the sound of a user are called “target sounds”, and signals other than the above signals are called “noise”.
  • the sound hole means a hole made in the casing of a communication terminal in order to guide sound to microphones in the casing of the communication terminal.
  • Non-Patent Literature 1 Acoustic Systems and Digital Processing For Them edited by the Institute of Electronics, Information and Communication Engineers
  • Patent Literature 1 JP-A-2007-27939
  • Patent Literature 2 JP-A-2004-289762
  • Fig. 17 is a configurational view showing the delay-and-sum type microphone array.
  • the output signal of the microphone 121 is delayed by delay devices 123 and 124 by Dsin0/c with respect to the microphone 122, the phases of the signals are adjusted, and the output signals are added by an adder 125, whereby a directivity having a beam (a direction of especially high sensitivity) in the direction ⁇ can be formed for the output signal 126 of the adder 125. Therefore, if the beam is turned to the direction in which the target sound comes, it is possible to suppress noise and to intensify the target sound. Also, although the interval D between the microphones is required to be equal to or less than one half (1/2) the wavelength in the upper limit frequency of input sound waves, the sensitivity of the entire microphone array will be lowered if the interval D between the microphones is too small.
  • Fig. 18A shows a directional characteristic of the output signal 126 of the adder 125.
  • the direction ⁇ of the target sound is set in the front side direction (angle 0°) of a plurality of microphones.
  • the difference in sensitivity between the direction ⁇ (angle 0°) and the direction of ⁇ 90° (the right angle) from ⁇ is only two to three dB, and a sharp beam cannot be formed. Therefore, the effect to intensify the target sound is hardly obtained.
  • the microphones are arranged with the number thereof increased to, for example, four to eight, the phases of the output signal are arranged by the delay device, and the output signals are added. Accordingly, since the scale of the microphone array and the cost of the components are increased, it is difficult to mount such a microphone array in a small-sized communication terminal for general use such as a mobile phone.
  • Fig. 18B shows a directional characteristic of an output signal 128 of the subtractor 127.
  • a directivity having a sharp null is formed in the direction ⁇ in the output signal 128 of the subtractor 127 even if the number of microphones is two. Therefore, an effect to suppress noise can be obtained by setting the null direction in the noise arriving direction.
  • the null formed by the output signal 128 is limited to one direction, and the null cannot be formed in a plurality of directions at one time. Therefore, noise coming from one direction can be suppressed, it is impossible to suppress noises coming from a plurality of directions at the same time.
  • Fig. 19 is a configurational view of an adaptive-filter-type microphone array, wherein a delay device 141 and an adaptive filter 142 are disposed instead of the delay devices 123 and 124 in Fig. 17.
  • the delay time of the delay device 141 is fixed at approximately D/c that is the maximum value in the delay time between two microphones.
  • the adaptive filter 142 is updated from time to time so that the output of the adder 143 is minimized.
  • the direction of noise by which a null can be formed is limited to one direction at the same time, where the accuracy of the adaptive filter will be lowered under the situation where noises simultaneously arriving from a plurality of directions, that is, ambient noises exist.
  • FIG. 20 is a schematic view of a microphone array of a two-channel SS system.
  • a target sound intensifier 153 for generating a beam in the direction of the target sound and a target sound attenuator 154 for forming a null in the direction of the target sound on the contrary are, respectively, connected to two microphones 151 and 152.
  • a two-channel SS operator 155 outputs an output signal 156 having a sharp beam in the direction of the target sound by the two-channel SS operator 155 subtracting an output signal of the target sound attenuator 154, that is, the ambient sound signal from the output signal of the target sound intensifier 153 in the frequency domain.
  • Figs. 21 A and 21 B are graphs of sensitivity characteristics obtained by the two-channel SS system, which show the sensitivity characteristics in a case where the target sound is in the front side direction, that is, the normal direction of two microphones.
  • a sharp beam is formed in the front side direction (angle 0°) in the output signal 156.
  • a curved beam will be formed in this system, except in a case where the direction in which the beam is formed is aligned with the extension line of two microphones.
  • the beam is formed along the curved surface on which a segment linking the microphones with the target sound is depicted by turning it with the extension line of the two microphones used as an axis. The state is shown in Fig.
  • a sound pickup apparatus is disposed in a planar-shaped casing, and directivity having a beam in the front side direction thereof is formed.
  • directivity having a beam in the front side direction thereof is formed.
  • delay/addition-type microphone array it is necessary to arrange a number of microphones. In this case, since the space and cost are increased, it becomes difficult to mount the microphones in a small-sized terminal.
  • the delay-and-subtraction type microphone array is not suitable for use for forming a beam in a desired direction.
  • the microphone array of the two-channel SS system which is described in Patent Literature 2, although a comparatively sharp beam can be formed with two microphones, the microphone array is still not suitable for the purpose of forming a beam only in the front side direction of the sound pickup apparatus as shown in Fig. 21 B.
  • Patent Literature 1 JP-A-2007-27939
  • Patent Literature 2 JP-A-2004-289762
  • Non Patent Literature 1 Acoustic Systems and Digital Processing For Them edited by the Institute of Electronics, Information and Communication Engineers and published in April, 1995
  • the present invention has been developed in view of such situations, and it is therefore an object of the invention to provide a sound pickup apparatus capable of forming a directivity having a sharp beam or a null in a specified direction by a microphone array composed of a small number of microphones, and a portable communication apparatus including the sound pickup apparatus, and an image pickup apparatus.
  • a sound pickup apparatus including: a microphone array including at least three microphones, wherein a first pair of microphones in which two of the at least three microphones are aligned on a first axis, and a second pair of microphones in which two of the at least three microphones are aligned on a second axis; a first null signal generator which outputs a first null signal based on a differential output of the first pair of microphones, the first null signal having a directional characteristic in which a first null surface is defined by rotating a virtual line extending toward a direction of the lowest sensitivity around the first axis; a second null signal generator which outputs a second null signal, based on a differential output of the second pair of microphones, the second null signal having a directional characteristic in which a second null surface is defined by rotating a virtual line extending toward a direction of the lowest sensitivity around the second axis; and a combiner which generates a
  • the sound pickup apparatus may further include a frequency domain subtractor which is adapted to perform subtraction in frequency domain of the first target signal from a signal output from one of the at least three microphones to output a second target signal.
  • a frequency domain subtractor which is adapted to perform subtraction in frequency domain of the first target signal from a signal output from one of the at least three microphones to output a second target signal.
  • a beam (a direction of especially high sensitivity) or a null (a direction of especially low sensitivity) is formed only in the direction of a target sound by means of a microphone array including at least three microphones, which can be easily mounted in a small-sized terminal, it is possible to achieve a sound pickup apparatus having favorable performance to suppress ambient sounds.
  • Fig. 1 is an appearance view of a communication apparatus according to Embodiment 1 of the present invention.
  • Fig. 2 is a block diagram of operations according to Embodiment 1 of the present invention.
  • Fig. 3 is a configurational view of components according to Embodiment 1 of the present invention.
  • Fig. 4 is a detailed block diagram of operations according to
  • Embodiment 1 of the present invention is a diagrammatic representation of Embodiment 1 of the present invention.
  • Fig. 5A and Fig. 5B are schematic views of target sound direction according to Embodiment 1 of the present invention.
  • Fig. 6 shows a state where a three-dimensional coordinate system in Fig. 5 is superimposed on the communication apparatus.
  • Fig. 7A through Fig. 7F are sensitivity graphs of a null signal generator according to Embodiment 1 of the present invention.
  • Fig. 8A through Fig. 8C are graphs showing the operation description of a combiner according to Embodiment 1 of the present invention.
  • Fig. 9 is a flowchart of the operation description of a combiner according to Embodiment 1 of the present invention.
  • Fig. 10A and Fig. 10B are sensitivity graphs of a combiner according to Embodiment 1 of the present invention.
  • Fig. 11 A and Fig. 11 B are sensitivity graphs of a frequency domain subtractor according to Embodiment 1 of the present invention.
  • Fig. 12 is a block diagram of operations according to Embodiment 2 of the present invention.
  • Fig. 13 is a block diagram of operations according to Embodiment 3 of the present invention.
  • Fig. 14A and Fig. 14B are appearance views of an image pickup apparatus according to Embodiment 3 of the present invention.
  • Fig. 15A and Fig. 15B are views describing modified versions of the present invention.
  • Fig. 16 describes another modified version of the present invention.
  • Fig. 17 is a configurational view of a delay/addition-type microphone array according to a background art.
  • Fig. 18A and Fig. 18B are views of directional characteristic of a delay/addition-type microphone array according to the background art.
  • Fig. 19 is a configurational view of an adaptive-filter-type microphone array according to the background art.
  • Fig. 20 is a schematic configurational view of a two-channel SS system according to the background art.
  • Fig. 21 A through Fig. 21 C are views of directional characteristic of a two-channel SS system according to the background art.
  • An aspect of the present invention provides a sound pickup apparatus, including: a microphone array including at least three microphones, wherein a first pair of microphones in which two of the at least three microphones are aligned on a first axis, and a second pair of microphones in which two of the at least three microphones are aligned on a second axis; a first null signal generator which outputs a first null signal based on a differential output of the first pair of microphones, the first null signal having a directional characteristic in which a first null surface is defined by rotating a virtual line extending toward a direction of the lowest sensitivity around the first axis; a second null signal generator which outputs a second null signal, based on a differential output of the second pair of microphones, the second null signal having a directional characteristic in which a second null surface is defined by rotating a virtual line extending toward a direction of the lowest sensitivity around the second axis; and a combiner which generates a first target signal
  • null a direction of especially low sensitivity
  • the sound pickup apparatus may further include a frequency domain subtractor which is adapted to perform subtraction in frequency domain of the first target signal from a signal output from one of the at least three microphones to output a second target signal.
  • a frequency domain subtractor which is adapted to perform subtraction in frequency domain of the first target signal from a signal output from one of the at least three microphones to output a second target signal.
  • one microphone of the first pair of microphones may be the same as one microphone of the second pair of microphones.
  • a sound pickup apparatus having favorable performance to suppress ambient sound by an easily mountable microphone array including at least three microphones, and the mounting cost can be reduced.
  • the first axis may intersect the second axis at right angles.
  • the sound pickup apparatus may be configured in that the combiner includes: a first FFT section which transforms the first null signal into a first frequency signal having a first frequency characteristic related to first frequency bins; a second FFT section which transforms the second null signal into a second frequency signal having a second frequency characteristic related to second frequency bins; and an operator which generates the first target signal based on the first frequency signal related to the first frequency bins and the second frequency signal related to the first frequency bins.
  • the operator may generate the first target signal by selecting each value of respective frequency bins of the first or second frequency signals, whichever is greater, in each frequency bin.
  • the ambient sound signal existing in both the sets and the ambient signals existing only in either one of them are reflected in the output signals of the ambient sound signal estimator by the same weighting, it becomes possible to uniformly lower the side lobe (the sensitivity in the direction other than the direction of target sound) in the output signals of the frequency domain subtractor.
  • the operator adds each value of the respective frequency bins of the first frequency signal to each value of the respective frequency bins of the second frequency signal.
  • null a direction of especially low sensitivity
  • each of the first and second null signal generators may include a delay device and a subtractor to be implemented as a delay-and-subtraction type microphone array.
  • a null is formed in an intended direction by the null signal generator applying a preset delay time to the delay device, wherein it becomes possible to form a beam in the intended direction in the output signals, of the frequency domain subtractor, obtained by using the same.
  • each of the first and second null signal generators may include a delay device and an adaptive filter to be implemented as an adaptive-type microphone array.
  • the null signal generator forms a null by automatically following the direction where the direction of the target sound is not obvious or fluctuates, it becomes possible to continuously form a beam having a high sensitivity in the direction of the target sound in the output signals, of the frequency domain subtractor, obtained by using the same.
  • the sound pickup apparatus may include an adjustor for adjusting individual differences in sensitivity of the at least three microphones to have the same sensitivity each other.
  • a portable communication apparatus including a display screen and the sound pickup apparatus disposed on a plane for arranging the display screen thereon.
  • the direction of the line along which the first null surface may meet the second null surface is fixed in a front direction of the display screen.
  • the direction of the line along which the first null surface may meet the second null surface automatically follows a direction of a target sound within a certain area centered around a front direction of the display screen.
  • a beam is formed, following the direction even if the direction of the speaker changes centering around the front side direction of the display screen, wherein such an effect can be brought about by which the sound of the speaker can be clearly picked up and a favorable communication quality is obtained.
  • a portable communication apparatus including a key pad and the sound pickup apparatus disposed on a plane for arranging the key pad thereon.
  • the sound pickup apparatus may be configured in that the first null signal generator generates a third null signal based on signals output from the first pair of microphones, and the second null signal generator generates a fourth null signal based on signals output from the second pair of microphones, and the combiner directs, based on the third null signal and the fourth null signal, a direction of a line along which a third null surface of the third null signal meets a fourth null surface of the fourth null signal toward a direction of another target sound to be picked up.
  • the apparatus since sound waves arriving from a plurality of directions are individually separated and picked up where a user utters from a plurality of directions, the apparatus is effective for a sound conference apparatus and a speech recognition apparatus.
  • the frequency domain subtractor may be adapted to perform the subtraction based on an arbitrary subtraction ratio.
  • an image pickup apparatus including a camera for capturing an image and the sound pickup apparatus, wherein the direction of the line along which the first null surface meets the second null surface is set to a direction of the image to be captured, and wherein the subtraction ratio is determined in conjunction with a zoom ratio of the camera.
  • an image pickup apparatus including a camera for capturing an image and the sound pickup apparatus, wherein a delay time of at least one of delay devices included in the first and second null signal generators is changed in response to a variation of a capturing direction of the camera so as to direct the line along which the first null surface meets the second null surface toward a direction of the image to be captured.
  • the beam direction can be followed to the direction, wherein such an effect can be brought about by which the image pickup screen and acoustic signals are continuously coincident with each other.
  • Fig. 1 is an appearance view showing a portable communication terminal 1 having a sound pickup apparatus according to Embodiment 1 mounted therein.
  • the communication terminal 1 has a thin casing provided with a display screen 14, a speaker 15, a key pad 16, and three non-directional microphones 11 , 12 and 13, etc.
  • the microphones 11 , 12 and 13 are disposed in the right-angle direction with the microphone 12 placed therebetween. It is assumed that the interval between the microphones 11 and 12 is Dx and the interval between the microphones 12 and 13 is Dy. That is, the respective microphones are disposed at the apexes of the right-angle triangle the short sides of which are Dx and Dy. Also, as the type of the microphones, it is desirable that a non-directional microphone is used in view of the cost.
  • a microphone having directivity may be used.
  • a user of the terminal carries out a communication operation by using the key pad 16 and carries out sound input by the microphones while watching the display screen 14.
  • the sound pickup apparatus 10 has a beam (a direction of especially high sensitivity) in the direction of the z axis when it is assumed that the direction from the microphone 12 to the microphone 11 is x axis, the direction from the microphone 12 to the microphone 13 is y axis, and the direction perpendicular to the x-y plane is z axis in a three-dimensional orthogonal coordinate system.
  • a microphone array 20 composed of three microphones 11 through 13 is mounted in the communication terminal 1 in Embodiment 1.
  • the sensitivity of the sound pickup apparatus 10 will be lowered if the interval is excessively small.
  • the analog output signal of the microphone is converted to a digital signal of a sampling frequency 16kHz
  • the upper limit of the frequency is 8kHz
  • the wavelength becomes 40mm or slightly more, wherein it is favorable that the intervals Dx and Dy between the microphones are 20mm or slightly less.
  • an adjustor for adjusting individual differences in the sensitivity of microphones is provided.
  • a coefficient for adjustment is preset in the adjustor, for example, before shipment. Therefore, influences due to individual differences with respect to microphone sensitivity are reduced.
  • Fig. 2 is a schematic block diagram of operations of the sound pickup apparatus 10 according to Embodiment 1 of the present invention.
  • the sound pickup apparatus 10 according to Embodiment 1 is provided with microphones 11 , 12 and 13, an X-direction null signal generator 21 , a Y-direction null signal generator 22, an ambient sound signal estimator 23, and a frequency domain subtractor 24, and outputs an output signal 25.
  • Fig. 3 is a hardware block diagram of the sound pickup apparatus 10 according to Embodiment 1 of the present invention.
  • the sound pickup apparatus 10 includes a DSP (Digital Signal Processor) 30 for executing various types of signal processing, a program memory 31 for storing program software to perform various types of signal processing in the DSP 30, a work memory 32 for operation, which is required to execute various types of programs stored in the program memory 31 in the DSP 30, and a non-volatile memory 33 to record the processing results, etc., of the DSP 30.
  • DSP Digital Signal Processor
  • An ADC Analog to Digital
  • analog signals that the microphones 11 through 13 output are subjected to signal processing in the DSP 30 after having been digitalized in the ADC 34. That is, respective processing of the
  • X-direction null signal generator 21 the Y-direction null signal generator 22, the ambient sound signal estimator 23 and the frequency domain subtractor 24 in the operation block in Fig. 2 are executed by the DSP 30.
  • the output signal 25 of the microphone array processing which is obtained as a result thereof, is output from the DSP 30 or is utilized for other signal processing in the DSP 30.
  • Fig. 4 shows an example of a detailed operation block, which composes respective operation blocks of signal processing in Fig. 2.
  • the X-direction null signal generator 21 includes delay devices 401 and 402 connected to the microphones 11 and 12, which become a first pair of microphones, disposed in the X-direction in Fig. 1 , and a subtractor 404.
  • the Y-direction null signal generator 22 includes delay devices 402 and 403 connected to the microphones 12 and 13, which become a second pair of microphones, disposed in the Y-direction in Fig. 1 , and a subtractor 405.
  • Y-direction null signal generators 21 and 22 having such a composition carry out processing called delay-and-subtraction type microphone array processing.
  • the delay device 402 connected to the microphone 12 is common to both of the X- and Y-direction null signal generators 21 and 22.
  • the ambient sound signal estimator 23 includes frame dividing sections 413 through 415, window framing sections 417 through 419, FFT sections 406 through 408, and a combiner 409.
  • the frequency domain subtractor 24 includes an attenuation filter calculator 410, a spectral attenuator 411 , an IFFT section 412, and a frame combiner 416.
  • the X-direction null signal generator 21 and the Y-direction null signal generator 22 form directivity having a null (a direction of especially low sensitivity) in the direction of the target sound in the output signal on the planes (x-z plane and y-z plane) defined by the x axis and the z axis, and the y axis and the z axis in Fig. 1 , respectively.
  • angle between a plane and a straight line is defined as follows.
  • a case is taken into consideration where the plane a crosses the straight line I at the intersection point P.
  • An optional point B on the straight line is taken, and a perpendicular line is drawn from the point B to the plane a.
  • the point at which the perpendicular line crosses the plane is determined to be H.
  • ZBPH is the angle ⁇ between the plane a and the straight line I.
  • Fig. 5B transcribes a three-dimensional orthogonal coordinate system in Fig. 1.
  • a single sound source (target sound) being an object of sound pickup such as a user of a terminal is positioned at point P in Fig. 5.
  • the X-direction null signal generator 21 forms directivity having a null in the direction of ⁇ .
  • ⁇ 1- ⁇ 2 Dx sin6x/c (c: acoustic velocity)
  • the phases of signals of the respective microphones 11 and 12 by the sound source P are made coincident with each other by giving a delay of Dx sin0x/c to the signal of the microphone 1 1 with respect to the signal of the microphone 12.
  • a null is formed in the direction of ⁇ in the output signal of the subtractor 404 by subtracting the output signal of the delay device 401 from the output signal of the delay device 402 by means of the subtractor 404.
  • the angle between the straight line r and the xz plane defined by the x axis and the z axis is made into 0y, wherein ZPOPx becomes 0y.
  • the relationship between the delay times ⁇ 2 and ⁇ 3 given by the delay devices 402 and 403 in Fig. 4 is set as shown in [Mathematical Expression 2]. Therefore, a null is formed in the direction of 6y in Fig. 5 in the output signal of the subtractor 405.
  • ⁇ 3- ⁇ 2 Dy sin9y/c (c: acoustic velocity)
  • x1 and x3 may be obtained as the already known fixed value as in [Mathematical Expression 3]. If the value of x2 is set to, for example, a value obtained by dividing either one of Dx or Dy, whichever is greater, by the acoustic velocity c, there is no case where x1 and x3 become negative in all the angle ranges that are obtainable by ⁇ and 0y.
  • x1 x2+Dx sin9x/c
  • Fig. 6 shows a state where the three-dimensional orthogonal coordinate system in Fig. 5B is superimposed on the communication terminal 1. It is considered that there are many cases where the point P exists on the z axis, that is, in the front side direction of the microphone array 20 in the communication terminal 1. In this case, since signals arrive at the respective microphones almost at the same time, no delay is brought about, wherein the delay times ⁇ 1 through ⁇ 3 may be set to zero or may all be set to the same value. Accordingly, a sharp beam is formed in the z-axis direction, that is, in the front side direction of the terminal with respect to the output signal of the entire sound pickup apparatus.
  • Fig. 7 A and Fig. 7B show a sensitivity graph of respective output signals by the X-direction and Y-direction null signal generators 21 and 22 in the case where a null signal is formed in the z-axis direction.
  • the x axis expresses the angle from the front side of the microphone
  • the y axis expresses the angle from the upper side of the microphone on the axis orthogonal to the x axis
  • the z axis expresses sensitivity. For example, when observing Fig.
  • FIG. 7B showing the sensitivity graph of the Y-direction null signal generator 22, although a sharp null is formed in the direction of 0° (parallel to the xy plane) with respect to the angle 0y, no null is formed with respect to ⁇ that seems to be the same angle from the two microphones 12 and 13.
  • the first null surface is orthogonal to the straight line linking the microphone 11 with the microphone 12, and the second null surface is orthogonal to the straight line linking the microphone 12 with the microphone 13.
  • the straight line linking the microphone 11 with the microphone 12 is made into an abscissa
  • a polar pattern in which a null is generated at the angle of 0° orthogonal to the abscissa can be generated.
  • the direction of the null surface can be varied.
  • the pattern is shown in Fig. 7C and Fig. 7D. This example shows a case where an angle of 35° is set by the difference between ⁇ 1 and x2.
  • the ideal condition is that the microphone is spot-shaped, and the difference in the phase of sound waves reaching the microphone is accurately obtained in accordance with the angle of the sound source.
  • Output signals of the X-direction null signal generator 21 , the delay device 402 and the Y-direction null signal generator 22 are divided into frame signals having a predetermined time length and interval by the frame dividing sections 413 through 415, respectively.
  • the output signals are divided so that sampling is carried out at 8kHz, the frame length is 128 points and the frame interval is 64 points. Therefore, the front half of the frame overlaps the latter half of the former frame, and the latter half of the frame overlaps the front half of the subsequent frame. This is to prevent the waveform from becoming discontinuous at the boundary of frames when the frames are combined and connected by the frame combiner 416 in the subsequent stage.
  • the window framing sections 417 through 419 carry out a window framing process on frame-by-frame divided signals so that frequency resolution accuracy required to perform an FFT process in a subsequent stage is obtained.
  • a Hanning window as shown in, for example, the next [Mathematical Expression 4] may be used as the window function.
  • the window function when the former frame is overlapped on the latter frame, the sums of the overlapped sections become equal to each other.
  • sample row obtained by processing the output of the subtractor 404 by the window framing section 417 is xx-R, N , where n is a sample number. It is assumed that the sample row obtained by processing the output of the subtractor 402 by the window framing section 418 is x R _ n .
  • the sample row obtained by processing the output of the subtractor 405 by the window framing section 419 is XY-R, N .
  • the processes of the FFT sections 406, 407 and 408 are shown in the following [Mathematical Expression 5].
  • the output of the FFT section 406 is expressed by XX-R iP
  • the output of the FFT section 407 is expressed by XR iP
  • the output of the FFT section 408 is expressed by XY-R ,P .
  • N is the total number of frequency bins
  • p is a frequency bin number
  • the frequency domain subtractor 24 carries out a subtraction process in the frequency domain using X R , P and XM, p with respect to all the frequencies p, and outputs a sample row xz ,n of the time domain.
  • H p that is the ratio of XR.P and X
  • p is calculated as in the [Mathematical Expression 7].
  • ⁇ is a coefficient to prevent the denominator from becoming zero.
  • H p ⁇ if H p > ⁇
  • the spectral attenuator 41 1 multiples the real part 9?[XR, p ] and the imaginary part 3[XR ,p ] of XR ,p by H p as in the [Mathematical Expression 8], and the real part 3 ⁇ 4[Xz,p] of Xz, p and the imaginary part 3[Xz, P ] thereof are obtained. Based on the above, XM ,p is subtracted from XR, p in the frequency domain.
  • the IFFT section 412 performs an inverse FFT calculation of
  • the frame combiner 416 combines continuous sound waveforms by adding the overlapped frames between the former and the latter frames one after another with respect to the frame-by-frame sample rows x z , n , and finishes combining.
  • Fig. 8A shows an example of amplitude spectrum
  • Fig. 8B shows an example of amplitude spectrum
  • the combiner 409 selects a greater amplitude value per frequency bin with respect to these two amplitude spectral signals, and combines a new amplitude spectral signal
  • Fig. 8C shows an example of the results. In Fig. 8C, values having a greater amplitude for respective frequency bins in Fig. 8A and Fig. 8B are selected and combined.
  • Fig. 9 shows a process for the combiner 409 to generate an amplitude spectral signal
  • the frequency bin number p is compared with the total number N of the frequency bins, and where p is smaller than N, the process advances to S12.
  • in the frequency bin number p are Sx,p and Sy,p, respectively
  • the value of Sx,p is compared with the value of Sy,p (S12).
  • Sx,p is equal to or greater than Sy,p (S12: YES),
  • S15 p is updated to the next number by adding 1 to the frequency pin number p. That is, amplitude values are selected for all the frequency bins. After all of the selection is over, the entire process is terminated (S11 : NO).
  • Power spectra may be calculated instead of the amplitude spectra in the ambient sound signal estimator 23, and the frequency filter bank may be used without carrying out the FFT process.
  • Fig. 10A shows a sensitivity graph of output signals of the combiner 409. Since the sensitivity graph in Fig. 10A shows a profile in which high sensitivity areas in Fig. 8A and Fig. 8B are combined with each other, the sensitivity is lowered toward only the intersection point of 0 degrees in the X axis and 0 degrees in the Y axis. A sharp null is formed in the straight line at which the first null surface in Fig. 7A and the second null surface in Fig. 7B cross each other, that is, in the direction of the Z axis.
  • the ambient sound signals existing in both output signals of the two sets of null signal generators and the ambient sound signal existing in only either one thereof are reflected onto the output signal of the ambient sound signal estimator at the same weighting, it becomes possible to uniformly lower the side lobe (the sensitivity in the direction other than the target sound) in the output signal of the frequency domain subtractor 24 described later.
  • Fig. 11A shows a sensitivity graph of output signals by the frequency domain subtractor 24. Since the output of the FFT section 407 shows uniform sensitivity characteristics in all the angular directions of ⁇ and 0y as the characteristics of the non-directional microphone, in the sensitivity graph obtained as a result of having subtracted the spectral components of the ambient sound signal, a pattern in which the null direction in the sensitivity graph of Fig. 10A is inverted to the beam (a direction of high sensitivity) is obtained. A beam can be directed in the straight line at which the first null surface in Fig. 7A and the second null surface in Fig. 7B cross each other, that is, in the direction of the Z axis. Therefore, as shown in Fig. 11 A, as a result of having subtracted the output signal of the combiner 409 in the frequency domain, a sensitivity graph of narrow directivity, in which the sensitivity is high in one direction of the target (that is, the direction of target sound) is obtained.
  • Embodiment 1 a description is given of a state where a selection process of spectra of the null signal in the X direction and the null signal in the Y direction is carried out.
  • the present invention is not limited thereto. That is, a simple addition calculation may be adopted with respect to the spectral addition.
  • Fig. 10B shows a sensitivity graph in which the spectra of null signals in the X direction and null signals in the Y direction are added. Also, the values in the drawing are the results of having performed normalization (the peak is adjusted to OdB).
  • a null is formed along the direction of 0 degrees in the X axis and the Y axis, respectively, in Fig. 8A and Fig. 8B. Therefore, if both are combined, an area having low sensitivity is partially formed in the vicinity of 0 degrees in the X axis and the Y axis as shown in Fig. 10B, and although being inferior to the sensitivity graph in Fig. 10A, which is brought about by the selection process, a signal having a sharp null in the target direction is output.
  • Fig. 11 B shows the output result of the frequency domain subtractor 24 using the signal.
  • Embodiment 1 according to the present invention which is achieved as described above, can form a sharp beam only in the target directions including the front side direction by a microphone array composed of a small number (three) of microphones, Embodiment 1 is suitable for the purpose of being incorporated in a small-sized apparatus as shown in Fig. 1 and executing sound pickup having few ambient sounds.
  • Fig. 12 is a block configurational view of a sound pickup apparatus according to Embodiment 2 of the present invention, and particularly shows block configuration of an X-direction null signal generator 221 and a Y-direction null signal generator 222.
  • two types of null signals are formed by an adaptive-filter-type microphone array, respectively.
  • the signal of microphone 11 is delayed by the delay device 401
  • the adaptive filter 244 performs filter calculations using the signal of the microphone 12 as input
  • the output signal of the adaptive filter 244 and the output signal of the delay device 401 are added to each other by the adder 241.
  • the filter coefficient is continuously updated so that the output signal of the adder 241 is minimized.
  • the adaptive filter 245 performs filter calculations using the signal of the microphone 12 as input, and the output signal of the adaptive filter 245 and the output signal of the delay device 403 are added to each other by the adder 243. And, in the adaptive filter 245, the filter coefficient is continuously updated so that the output signal of the adder 243 is minimized.
  • the configurations of the ambient sound signal estimator 23 and the frequency domain subtractor 24, which come in the subsequent stage, are similar to those of Embodiment 1.
  • Such an adaptive filter can be achieved by an algorithm such as the LMS (Least Mean Square) method and the learning identification method.
  • LMS Least Mean Square
  • AMNOR Adaptive Microphone array for NOise Reduction
  • the X-direction null signal generator 221 and the Y-direction null signal generator 222 automatically detect the direction of the target sound on the respective axes and can continuously form a null in the direction.
  • Respective null signals output from the X-direction null signal generator 221 and the Y-direction null signal generator 222 are corrected by the combiner 409 of the ambient sound signal estimator 23. As a result, such an effect can be obtained by which a sharp beam is continuously formed only in the direction of the target sound in the output 225 of the frequency domain subtractor 24.
  • Embodiment 3 according to the present invention with reference to Fig. 13 and Fig. 14A, 14B.
  • Fig. 13 is a block configurational view of a sound pickup apparatus according to Embodiment 3 of the present invention.
  • a target sound direction information section 341 , an attenuation ratio setting section 342 and a sound pickup magnification information section 343 are added to the configuration of Embodiment 1.
  • the sound pickup apparatus according to the present embodiment is incorporated in an image pickup apparatus 301 such as a video camera, etc., as shown in Fig. 14A and Fig. 4B.
  • the sections that overlap the components of Embodiment 1 are given the same reference numerals, and detailed description thereof is omitted.
  • Fig. 14A and Fig. 14B are perspective views of the image pickup apparatus 301 including three microphones 11 through 13.
  • the image pickup apparatus 301 shown in Fig. 14A includes an image pickup section 302 and microphones 11 through 13 disposed in the image pickup apparatus 301.
  • the image pickup apparatus 301 shown in Fig. 14B includes an image pickup section 302 and a microphone accommodation section 304 that is connected to the image pickup section 302 via a communication line and is separated from the image pickup section 302.
  • the microphones 11 through 13 are incorporated in the microphone accommodation section 304.
  • the components, other than the microphones 11 through 13, of the sound pickup apparatus 10 described in Embodiment 1 may be
  • connection between the microphone accommodation section 304 and the image pickup section 302 may be implemented by wireless communications instead of a communication line.
  • the target sound direction information section 341 shown in Fig. 13 acquires information on the image capturing direction from the image pickup apparatus 301 , and determines the target direction for sound pickup (that is, the direction of target sound) based on the information.
  • the direction of the target sound is determined to be the center of the image capturing direction of the image pickup section 302.
  • the X-direction and Y-direction null signal generators 21 and 22 can form a null signal in the center direction in the image pickup screen.
  • a null and a beam are, respectively, formed in the target sound direction by the ambient sound signal estimator 23 and the frequency domain subtractor 324.
  • the microphones 11 through 13 are disposed in the form that the pan (horizontal) direction of the image pickup section 302 corresponds to the X axis, and the tilt (vertical) direction corresponds to the Y axis.
  • the Z axis corresponds to the image capturing direction of a camera in the default state of the image pickup section 302 (that is, in a state where the camera is not panned or tilted).
  • the image pickup section 302 When the image pickup section 302 is moved in the horizontal direction from the default state, the image capturing direction, that is, the target sound direction moves on the X axis. That is, ⁇ becomes a greater value than 0°. Also, when the image pickup section 302 is moved in the vertical direction from the default state, the image capturing direction, that is, the target sound direction moves on the Y axis. That is, 6y becomes a greater value than 0°.
  • the delay time that determines the direction of the directivity of sound pickup when ⁇ and 9y change and is given to the delay devices x1 and ⁇ 3 in Fig. 4 is given, as in [Mathematical Expression 3] by referencing ⁇ 2. Therefore, a null can be formed to follow the image capturing direction in null signals output from the X-direction null signal generator 21 and the Y-direction null signal generator 22. As a result, it becomes possible that the null direction of the null signal output by the ambient sound signal estimator 23 is coincident with the image capturing direction, and the beam direction of the beam signal output by the frequency domain subtractor 324 is coincident with the image capturing direction.
  • the sound pickup magnification information section 343 acquires information on the zoom ratio of image pickup from the image pickup apparatus 301 , and sets the degree of the level by which the ambient sound signals are subtracted in the attenuation ratio setting section 342, wherein the level of directivity of the sound pickup apparatus is changed over.
  • [Mathematical Expression 10] it is possible to adjust the level of the directivity by multiplying the coefficient H p of [Mathematical Expression 7] by an
  • target sound direction information section 341 may be independently provided, or only the attenuation ratio setting section 342 and the sound pickup magnification information section 343 may be provided.
  • the target sound direction was set to the center in the image capturing direction of the image pickup section 302
  • the target sound direction may be set to the direction based on the result obtained from a calculation using parameters preset in the target sound direction information section 341 with respect to the information on the acquired image capturing direction.
  • a sound pickup apparatus having favorable performance to suppress ambient sounds has been achieved by forming a beam (the point of especially high sensitivity) in the target sound direction.
  • a beam the point of especially high sensitivity
  • the arrangement of the microphones is not limited to the right angle. That is, the relationship may be acceptable in which the axes on which the first pair of the microphones 11 and 12 and the second pair of the microphones 12 and 13 are disposed cross each other so that the microphones 11 and 12 composing the first pair and the microphones 12 and 13 composing the second pair can form a null in different directions. In this case, although the accuracy of a beam of the output signal of the frequency domain subtractor 24 is lowered more or less, the degree of freedom to dispose the microphones is increased.
  • the configuration is effective for a case where there is a restriction in arrangement of microphones as in a small-sized terminal such as a mobile phone.
  • a folding-type communication terminal 1 was assumed.
  • the sound pickup apparatus is incorporated in, for example, a straight-type portable terminal 501.
  • the display screen 514 of the portable terminal 501 and the microphones 11 through 13 are disposed on the same plane, it becomes possible to form a beam in the direction of an image being picked up while displaying an image being picked up by means of, for example, a camera on the display screen 514, wherein convenience of the user can be improved.
  • the microphones 11 through 13 may be disposed on the same plane as that of the display screen 14.
  • the microphone 12 of the three microphones 11 through 13 is used as a common microphone to form a null in the X direction and the Y direction.
  • the common microphone to form a null in the X direction and the Y direction may not be prepared, such a configuration may be adopted in which a null is formed separately in the X direction and the Y direction. That is, as shown in Fig. 15B, four microphones 521 through 524 are prepared, wherein the microphones 521 and 522 that become the first pair are used to form a null in the X direction with the interval Dx therebetween, and the microphones 523 and 524 that become the second pair are used to form a null in the Y direction with the interval Dy therebetween.
  • a signal having a sharp beam (or a null) formed in the target sound direction can be generated.
  • any one of the four microphones 521 through 524 or another microphone prepared may be used in the frequency domain subtractor 24 as a microphone showing non-directivity, which is used to generate a beam signal from a null signal in the target sound direction and shows a uniform sensitivity characteristic in all the angular directions.
  • a beam is formed in one certain target sound direction.
  • a beam may be formed in a plurality of directions.
  • Fig. 16 shows a block diagram to form a null in two target sound directions. Signals picked up by the microphone 11 are separated into the delay devices 401 and 401', and the delay times x1 and ⁇ 1' are set for the respective separated signals. With respect to the signals picked up by the microphones 12 and 13, the delay times x2, ⁇ 2', ⁇ 3, ⁇ 3' are set by the delay devices 402, 402' and the delay devices 403, 403' as well.
  • a beam or a null can be formed only in the target sound direction by a microphone array composed of at least three microphones, it is possible to achieve a sound pick apparatus that can be easily mounted in a small-sized terminal, and has favorable performance to suppress ambient sounds.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • General Health & Medical Sciences (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Abstract

L'appareil de prise de son (10) selon l'invention comporte : une matrice de microphones (20) comprenant au moins trois microphones (11-13) avec une première paire de microphones (11, 12) alignée sur un premier axe (X) et une seconde paire de microphones (12, 13) alignée sur un second axe (Y) ; un premier générateur de signal zéro (21) qui émet un premier signal zéro sur la base d'une sortie différentielle de la première paire de microphones (11, 12) ; un second générateur de signal zéro (22) qui émet un second signal zéro sur la base d'une sortie différentielle de la seconde paire de microphones (12, 13) ; et un combinateur (409) qui génère un signal cible sur la base du premier signal zéro et du second signal zéro, le signal cible ayant une caractéristique directionnelle dans laquelle la sensibilité la plus basse est formée dans une direction vers une ligne le long de laquelle la première surface zéro rencontre la seconde surface zéro.
PCT/JP2010/052482 2010-02-12 2010-02-12 Appareil de prise de son, appareil de communication portable et appareil de prise d'image WO2011099167A1 (fr)

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EP2690886A1 (fr) * 2012-07-27 2014-01-29 Nokia Corporation Procédé et appareil pour la formation de faisceaux de microphone
WO2017058192A1 (fr) * 2015-09-30 2017-04-06 Hewlett-Packard Development Company, L.P. Suppression des bruits ambiants
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JP2019169855A (ja) * 2018-03-23 2019-10-03 沖電気工業株式会社 収音装置、プログラム及び方法
CN112071332A (zh) * 2019-06-11 2020-12-11 阿里巴巴集团控股有限公司 确定拾音质量的方法及装置
CN114885085A (zh) * 2022-06-15 2022-08-09 西安应用光学研究所 一种基于磁栅尺的寻零精确定位方法

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EP2690886A1 (fr) * 2012-07-27 2014-01-29 Nokia Corporation Procédé et appareil pour la formation de faisceaux de microphone
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CN106658323A (zh) * 2017-02-28 2017-05-10 浙江诺尔康神经电子科技股份有限公司 人工耳蜗及助听器的双麦克风降噪***和方法
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JP7040198B2 (ja) 2018-03-23 2022-03-23 沖電気工業株式会社 収音装置、プログラム及び方法
CN112071332A (zh) * 2019-06-11 2020-12-11 阿里巴巴集团控股有限公司 确定拾音质量的方法及装置
CN114885085A (zh) * 2022-06-15 2022-08-09 西安应用光学研究所 一种基于磁栅尺的寻零精确定位方法
CN114885085B (zh) * 2022-06-15 2024-03-29 西安应用光学研究所 一种基于磁栅尺的寻零精确定位方法

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