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`US 8,861,756 B2
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`adaptivelyfiltering said ambient noise signals in each of
`tion, a sound sourcelocalization unit, an adaptive beam-
`said frequency sub-bands by said adaptivefilter matrix
`forming unit, and a noise reduction unit, wherein said
`in response to detecting one of presence and absence of
`sound source localization unit, said adaptive beamform-
`said target sound signal in said sound signals received
`ing unit, and said noise reduction unit are in operative
`from said disparate sound sources; and
`communication with said array of said sound sensors;
`synthesizing a full-band soundsignal using said frequency
`receiving said sound signals from a plurality of disparate
`sub-bandsof said enhanced target sound signal by said
`sound sources by said sound sensors, wherein said
`synthesis filter bank.
`received sound signals comprise said target sound signal
`6. The method of claim 3, wherein said adaptive beam-
`from a target sound source amongsaid disparate sound
`forming further comprises detecting said presence of said
`sources, and ambient noisesignals;
`target sound signal by an adaptation control unit provided in
`determining a delay between each of said sound sensors
`said adaptive beamforming, unit and adjusting a step size for
`and an origin of said array of said sound sensors as a
`function of distance between each of said sound sensors
`said adaptive filtering in response to detecting one ofsaid
`presence and said absence of said target sound signalin said
`and saidorigin, a predefined angle between cachofsaid
`sound signals received from said disparate sound sources.
`sound sensors anda reference axis, and an azimuth angle
`7. The method of claim 1, wherein said noise reduction unit
`between said reference axis and said target soundsignal,
`performs noise reduction by using one of a Wiener-filter
`when said target sound source that emits said target
`based noise reduction algorithm, a spectral subtraction noise
`soundsignalis in a two dimensionalplane, wherein said
`reduction algorithm, an auditory transform based noise
`delay is represented in terms of number of samples, and
`reduction algorithm, and a model based noise reduction algo-
`wherein said determination ofsaid delay enables beam-
`rithm.
`forming, for arbitrary numbersofsaid sound sensors and
`8. The methodof claim 1, wherein said noise reduction unit
`a plurality of arbitrary configurations of said array of
`said sound sensors;
`performs noise reduction in a plurality of frequency sub-
`bands, wherein said frequency sub-bands are employed by an
`estimating a spatial location of said target sound signal
`analysis filter bank of said adaptive beamforming unit for
`from said received sound signals by said sound source :
`localization unit;
`sub-band adaptive beamforming.
`9. A system for enhancing a target sound signal from a
`performing adaptive beamformingfor steering a directivity
`plurality of sound signals, comprising:
`pattern ofsaid arrayof said sound sensorsin a direction
`an array of sound sensors positioned in an arbitrary con-
`ofsaid spatial location of said target sound signalby said
`figuration, wherein said sound sensors receive said
`adaptive beamforming unit, wherein said adaptive
`sound signals from a plurality of disparate sound
`beamforming unit enhancessaid target sound signal and
`sources, wherein said received sound signals comprise
`partially suppresses said ambient noise signals; and
`said target sound signal from a target sound source
`suppressing said ambientnoise signals by said noise reduc-
`amongsaid disparate sound sources, and ambient noise
`tion unit for further enhancing said target soundsignal.
`signals;
`2. The methodofclaim 1, whereinsaid spatial location of
`a sound source localization unit that estimates a spatial
`said target sound signal from said target sound source is
`location of said target sound signal from said reecived
`estimated using a stcered response power-phase transform by
`said sound sourcelocalization unit.
`sound signals, by determining a delay between each of
`said sound sensors and an origin of said array of said
`3. The method of claim 1, wherein said adaptive beam-
`sound sensors as a function of distance between each of
`forming comprises:
`said sound sensors and said origin, a predefined angle
`providing a fixed beamformer, a blocking matrix, and an
`between each of said sound sensors and a reference axis,
`adaptivefilter in said adaptive beamforming unit;
`and an azimuth angle between said reference axis and
`steering said directivity pattern of said array of said sound
`said target sound signal, whensaid target sound source
`sensors in said direction of said spatial location of said
`that emits said target sound signal is in a two dimen-
`target sound signal from said target sound source by said
`sional plane, wherein said delay is represented in terms
`fixed beamformer for enhancing said target sound sig-
`of number of samples, and wherein said determination
`nal, when said target sound source is in motion;
`of said delay enables beamforming for arbitrary num-
`feeding said ambientnoise signals to said adaptive filler by
`bers of said sound sensors and a plurality of arbitrary
`blocking said target sound signal received from said
`configurations of said array of said sound sensors:
`target sound source using said blocking matrix; and
`an adaptive beamformingunitthat steers directivity pattern
`adaptively filtering said ambient noise signals by said
`adaptive filter in response to detecting one of presence of said array of said sound sensorsinadirection of said
`
`and absence of said target sound signal in said sound
`spatial location ofsaid target soundsignal, wherein said
`signals received from said disparate sound sources.
`adaptive beamforming unit enhancessaid. target sound
`4. The method of claim 3, wherein said fixed beamformer
`signal and partially suppresses said ambient noise sig-
`nals; and
`performsfixed beamformingbyfiltering and summingoutput
`sound signals [rom said sound sensors.
`a noise reduction unit thal suppresses said ambient noise
`5. The method ofclaim 3, whereinsaid adaptive filtering
`signals for further enhancing said target sound signal.
`comprises sub-band adaptive filtering performed by said
`10. The system of claim 9, wherein said sound source
`adaptivefilter, wherein said sub-band adaptive filtering com-
`localization unit estimates said spatial location of said target
`prises:
`sound signal from said target sound source using a steered
`providing, an analysisfilter bank, an adaptive filter matrix,
`response power-phase transform.
`and a synthesisfilter bank in said adaptivefilter;
`11. The system of claim 9, wherein said adaptive beam-
`splitting said enhanced target sound signal from said fixed
`forming unit comprises:
`beamformer and said ambient noise signals from said
`a fixed beamformerthat steers said directivity pattern of
`blocking matrix into a plurality of frequency sub-bands
`said array of said sound sensorsin said direction of said
`by said analysisfilter bank;
`spatial location of said target sound signal from said
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`US 8,861,756 B2
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`receiving said sound signals from a plurality of disparate
`target sound source for enhancing said target sound sig-
`sound sources by said sound sensors, wherein said
`nal, when said target sound source is in motion;
`received sound signals comprisesaid target sound signal
`a blocking matrix that feeds said ambient noise signals to
`from a target sound source amongsaid disparate sound
`an adaptive filter by blocking said target sound signal
`sources, and ambient noise signals;
`received from said target sound source; and
`determining a delay between each of said sound sensors
`said adaptivefilter that adaptivelyfilters said ambient noise
`and an origin of said array of said sound sensors as a
`function of distance between cach of said sound sensors
`signals in response to detecting one of presence and
`absenceofsaid target soundsignal in said sound signals
`and said origin, a predefined angle between each ofsaid
`received from said disparate sound sources.
`sound sensors and a first reference axis, an elevation
`12. The system ofclaim 11, wherein said fixed beamformer
`angle between a second reference axis and said target
`sound signal, and an azimuth angle betweensaid first
`performsfixed beamformingbyfiltering and summingoutput
`reference axis and said target sound signal, when said
`sound signals [rom said sound sensors.
`larget sound sourcethat emils said target sound signal is
`13. The system of claim 11, wherein said adaptive filler
`in a three dimensional plane, wherein said. delayis rep-
`comprises a set of sub-band adaptivefilters comprising:
`resented in terms of number of samples, and wherein
`an analysisfilter bank that splits said enhanced target sound
`said determination of said delay enables beamforming
`signal trom said fixed beamformer and said ambient
`for arbitrary numbers of said sound sensors and a plu-
`noise signals from said blocking matrix into a plurality
`rality of arbitrary configurations of said array ofsaid
`of frequency sub-bands;
`sound sensors;
`an adaplive filter matrix that adaptively fillers said ambient
`estimating a spatial location of said target sound signal
`noise signals in each ofsaid frequency sub-bands in
`from said received sound signals by said sound source
`response to detecting one of presence and absence of
`localization unit;
`said target sound signal in said sound signals received
`performing adaptive beamforming for steering a directivity
`from said disparate sound sources; and
`pattern ofsaid array of said sound sensorsin a direction
`a synthesis filter bank that synthesizes a full-band sound .
`of said spatial locationofsaid target sound signalby said
`signal using said frequency sub-bandsof said enhanced
`adaplive beamforming unil, wherein said adaptive
`target sound signal.
`beamforming unit enhancessaid target sound signal and
`14. The system of claim 9, wherein said adaptive beam-
`partially suppresses said ambient noise signals; and
`forming, unit further comprises an adaptation control unit that
`suppressing said ambient noise signals bysaid noise reduc-
`detects said presenceofsaid target sound signal and adjusts a
`tion unit for further enhancing said target sound signal.
`step size for said. adaptive filtering in response to detecting
`21. A system for enhancing a target sound signal from a
`one of said presence and said absence of said target sound
`plurality of sound signals, comprising:
`signal in said sound signals received from said disparate
`an array of sound sensors positioned in an arbitrary con-
`sound sources.
`figuration, wherein said sound sensors receive said
`15. The system of claim 9, wherein said noise reduction
`sound signals from a plurality of disparate sound
`unit is one of a Wiencr-filter based noise reduction unit, a
`sources, wherein said received sound signals comprise
`spectral subtraction noise reduction unit, an auditory trans-
`said target sound signal from a target sound source
`form based noise reduction unit, and a model based noise
`reduction unit.
`amongsaid disparate sound sources, and ambient noise
`signals:
`16. The system of claim 9, further comprising one or more
`a sound source localization unit that estimates a spatial
`audio codecsthat convert said soundsignals in an analog form
`location of said target sound signal from said. recerved
`of said soundsignals into digital sound signals and reconverts
`sound signals as a function of distance between cach of
`said digital soundsignals into said analog formof said sound
`said sound sensors and said origin, a predefined angle
`signals.
`between each of said sound sensors anda first reference
`17. The system of claim 9, wherein said noise reduction
`axis, an elevation angle between a secondreference axis
`unit performs noise reduction in a plurality of frequency
`and said target sound signal, and an azimuth angle
`sub-bands employed by an analysis filter bank of said adap-
`between said first reference axis and said target sound
`tive beamforming unit for sub-band adaptive beamforming.
`signal, when said target sound source that emits said
`18. The system ofclaim 9, wherein said array of said sound
`target sound signal is in a three dimensional plane,
`sensorsis onc ofa lincararrayofsaid sound sensors, acircular
`wherein said delay is represented in terms of number of
`array of said sound sensors, and an arbitrarily distributed
`samples, and wherein said determination of said delay
`coplanar array of said sound sensors.
`enables beamforming for arbitrary numbers of said
`19. ‘lhe method of claim 1, wherein said delay (t) is deter-
`sound sensors anda plurality of arbitrary configurations
`mined bya formula t=f,*t, wherein f, is a sampling frequency
`ofsaid array ofsaid sound sensors;
`and t is a time delay.
`an adaptive beamformingunit that steers directivity pattern
`20. A method for enhancing a target sound signal from a
`of said array of said sound sensorsinadirection of said
`plurality of sound signals, comprising:
`spatial location of said target sound signal, wherein said
`providing a microphonearray system comprising an array
`adaptive beamforming unit enhancessaid target sound
`of sound sensors positioned in an arbitrary configura-
`signal and partially suppresses said ambient noise sig-
`tion, a sound sourcelocalization unit, an adaptive beam-
`nals; and
`forming, unit, and a noise reduction unit, wherein said
`a noise reduction unit that suppresses said ambient noise
`sound source localization unit, said adaptive beamform-
`signals for further enhancing said largel sound signal.
`ing unit, and said noise reduction unit are in operative
`eo
`*
`* FF
`communication with said array of said sound sensors;
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`US 8,861,756 B2
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`1
`MICROPHONE ARRAY SYSTEM
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This application claims the benefit of provisional patent
`application No. 61/403,952 titled “Microphone array design
`and implementation for telecommunications and handheld
`devices”, filed on Sep. 24, 2010 in the United States Patent
`and Trademark Office.
`The specification of the above referenced patent applica-
`tion is incorporated. herein by reference in its entirety.
`
`BACKGROUND
`
`Microphonesconstitute an important clement in today’s
`speech acquisition devices. Currently, most of the hands-free
`speech acquisition devices, for example, mobile devices,
`lapels, headsets, etc., convert sound into electrical signals by
`using a microphone embedded within the speech acquisition
`device. However, the paradigm of a single microphone often
`does not work effectively because the microphone picks up
`many ambientnoise signals in additionto the desired sound,
`specifically when the distance between a user and the micro-
`phoneis more than a few inches. Therefore, there isanced for :
`a microphonesystem that operates undera variety ofdifferent
`ambient noise conditions and that places fewer constraints on
`he user with respect to the microphone, therebyeliminating
`he need to wear the microphoneorbe in close proximity to
`he microphone.
`To mitigate the drawbacks of the single microphonesys-
`em, there is a need for a microphone array that achieves
`directional gain in a preferred spatial direction while sup-
`pressing ambient noise from other directions. Conventional
`microphonearrays include arrays that are typically developed
`or applications such as radar and sonar, but are generally not
`suitable for hands-free or handheld speech acquisition
`devices. The main reason is that the desired sound signal has
`an extremely wide bandwidth relative to its center frequency,
`hereby rendering conventional narrowband techniques
`employedin the conventional microphone arrays unsuitable.
`n order to cater to such broadband speech applications, the
`array sizc needs to be vastly increased, making the conven-
`ional microphonearrays large and bulky, and precluding the
`conventional microphonearrays from having broader appli-
`cations, for example, in mobile and handheld communication
`devices. There is a need for a microphonearray system that
`provides an effective response over a wide spectrum offre-
`quencies while being unobtrusive in termsofsize.
`Hence, there is a long felt but unresolved need for a broad-
`band microphonearray and broadband beamforming system
`that enhances acoustics of a desired sound signal while sup-
`pressing ambient noise signals.
`
`2
`source, for example, a person’s speech that needs to be
`enhanced. A microphonearray system comprising an array of
`sound sensors positioned in an arbitrary configuration, a
`sound source localization unit, an adaptive beamforming
`unit, anda noise reduction unit, is provided. The sound souree
`localization unit, the adaptive beamforming unit, and the
`noise reduction unil are in operative communication with the
`array of sound sensors. The array of sound sensors is, for
`example, a linear array of sound sensors, a circular array of
`sound sensors, or an arbitrarily distributed coplanar array of
`sound sensors. The array of sound sensors herein referred to
`as a “microphonearray”receives sound signals from multiple
`disparate sound sources. ‘The method disclosed herein can be
`applied on a microphone array with an arbitrary number of
`sound sensors having, for example, an arbitrary two dimen-
`sional (2D) configuration. The sound signals received by the
`sound sensors in the microphonearray comprise the target
`sound signal from the target sound source amongthe dispar-
`ate sound sources, and ambientnoise signals.
`The sound sourcelocalization unit estimates a spatial loca-
`tion of the target sound signal from the received sound sig-
`nals, for example, using a steered response power-phase
`transform. The adaptive beamforming unit performs adaptive
`beamforming for steering a directivity pattern of the micro-
`phonearray in a direction of the spatial location of the target
`sound signal. The adaptive beamforming unit
`thereby
`enhances the target sound signal from the target sound source
`and partially suppresses the ambient noise signals. The noise
`reduction unit suppresses the ambient noise signals for fur-
`ther enhancing the target sound signal received from the
`target sound source.
`Tn an embodiment wherethe target sound source that emits
`the target sound signal is in a two dimensionalplane, a delay
`between each ofthe sound sensors andan origin ofthe micro-
`phonearray is determined as a function ofdistance between
`each of the sound sensors and the origin, a predefined angle
`between cach of the sound sensors and a reference axis, and
`an azimuth angle between the reference axis and the target
`sound signal. In another embodiment wherethe target sound
`source that emits the target sound signalis in a three dimen-
`sionalplane, the delay between each ofthe sound sensors and
`the origin ofthe microphonearrayis determined as a function
`of distance between each of the sound sensors andthe origin,
`a predefined angle between each of the sound sensors and a
`first reference axis, an elevation angle between a second
`reference axis and the target sound signal, and an azimuth
`angle between the first reference axis and the target sound
`signal. This method of determining the delay enables beam-
`forming for arbitrary numbers of sound sensors and multiple
`arbitrary microphonearray configurations. The delayis deter-
`mined, for example, in terms of number of samples. Once the
`delay is determined, the microphonearray can be aligned to
`enhancethe target sound signal froma specific direction.
`The adaptive beamforming unit comprises a fixed beam-
`former, a blocking matrix, and an adaptive filter. The fixed
`beamformersteers the directivity pattern of the microphone
`array in the direction ofthe spatial location of the target sound
`signal fromthe target sound source for enhancing the target
`sound signal, when the target sound sourceis in motion. The
`blocking matrix feeds the ambient noise signals to the adap-
`tive filter by blocking the target sound signal from the target
`sound source. The adaptivefilter adaptively filters the ambi-
`ent noise signals in response to detecting the presence or
`absence of the target sound signal
`in the sound signals
`received from the disparate sound sources. The fixed beam-
`formerperformsfixed beamforming,for example,byfillering
`and summing output sound signals from the sound sensors.
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`SUMMARYOF THE INVENTION
`
`This summary is provided to introduce a selection of con-
`cepts in a simplified form that are further described in the
`detailed description of the invention. This summary is not
`intendedto identify key or essential inventive concepts ofthe
`claimed subject matter, nor is it intended for determining the
`scope of the claimed subject matter.
`The method and system disclosed herein addresses the
`abovestated need for cnhancing acoustics of a target sound
`signal received from a target sound source, while suppressing
`ambient noise signals. As used herein, the term “target sound
`signal”refers to a sound signal froma desired or target sound
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`3
`In an embodiment, the adaptive filtering comprises sub-
`band adaptive filtering. The adaptive filter comprises an
`analysis filter bank, an adaptive filter matrix, and a synthesis
`filter bank. The analysis filter bank splits the enhancedtarget
`sound signal from the fixed beamformer and the ambient
`noise signals from the blocking matrix into multiple fre-
`quency sub-bands. The adaptive filter matrix adaptively fil-
`ters the ambient noise signals in each of the frequency sub-
`bandsin responseto detecting the presence or absenceof the
`target sound signal in the sound signals received from the
`disparate sound sources. The synthesis filter bank synthesizes
`a full-band soundsignalusing the frequency sub-bandsofthe
`enhancedtarget soundsignal. In an embodiment, the adaptive
`beamforming unit further comprises an adaptation control
`unit for detecting the presence of the target sound signal and
`adjusting a step size for the adaptive filtering in response to
`detecting the presence or the absence of the target sound
`signal in the sound signals received from the disparate sound
`sources.
`
`The noise reduction unit suppresses the ambient noise sig-
`nals for further enhancing the target sound signal from the
`target sound source. The noise reduction unit performs noise
`reduction, for example, by using a Wiener-filter based noise
`reduction algorithm, a spectral subtraction noise reduction
`algorithm, an auditory transform based noise reduction algo-
`rithm, or a model based noise reduction algorithm. The noise
`reduction unit performs noise reduction in multiple frequency
`sub-bands employed for sub-band adaptive beamforming by
`the analysis filter bank of the adaptive beamforming unit.
`The microphonearray system disclosed herein comprising
`the microphone array with an arbitrary number of sound
`sensors positioned in arbitrary configurations can be imple-
`mented in handheld devices, for example, the iPad® ofApple
`Inc., the iPhone® of Apple Inc., smart phones, tablet com-
`puters, laptop computers, etc. The microphonearray system
`disclosed herein can further be implemented in conference
`phones, video conferencing applications, or any device or
`equipmentthat needs better speech inputs.
`BRIEF DESCRIPTION OF‘THE DRAWINGS
`
`The foregoing summary, as well as the following detailed
`description ofthe invention,is better understood whenread in
`conjunction with the appended drawings. For the purpose of
`illustrating the invention, exemplary constructions of the
`invention are shown in the drawings. However,the invention
`is not limited to the specific methods and instrumentalities
`disclosed herein.
`FIG. 1 illustrates a method for enhancing a target sound
`signal from multiple soundsignals.
`FIG.2 illustrates a system for enhancing a target sound
`signal from multiple soundsignals.
`FIG. 3 exemplarily illustrates a microphone array configu-
`ration showing a microphonearray having N sound sensors
`arbitrarily distributed on a circle.
`FIG.4 exemplarilyillustrates a graphical representation of
`a filter-and-sum beamfonningalgorithm for determining oul-
`put of the microphone array having N soundsensors.
`FIG. 5 exemplarily illustrates distances between an origin
`of the microphone array and sound sensor M, and sound
`sensor M, in the circular microphone array configuration,
`whenthe target sound signal is at an angle @ fromthe Y-axis.
`TIG. 6A exemplarily illustrates a table showing the dis-
`tance between cach sound sensor in a circular microphone
`array configuration from the origin of the microphonearray,
`when the target sound sourceis in the sameplane asthat of the
`microphonearray.
`
`— 0
`
`a 5
`
`Nyc
`
`tv25
`
`35
`
`45
`
`SO
`
`55
`
`4
`FIG. 6B exemplarilyillustrates a table showing the rela-
`tionship of the position of each