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WO2003086009A1 - Agencement de reseaux de microphones a geometrie commutee, et procede de traitement de sorties d'une pluralite de microphones - Google Patents

Agencement de reseaux de microphones a geometrie commutee, et procede de traitement de sorties d'une pluralite de microphones Download PDF

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Publication number
WO2003086009A1
WO2003086009A1 PCT/EP2003/000789 EP0300789W WO03086009A1 WO 2003086009 A1 WO2003086009 A1 WO 2003086009A1 EP 0300789 W EP0300789 W EP 0300789W WO 03086009 A1 WO03086009 A1 WO 03086009A1
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WO
WIPO (PCT)
Prior art keywords
microphones
array
switched
outputs
geometry
Prior art date
Application number
PCT/EP2003/000789
Other languages
English (en)
Inventor
David Pearce
James Rex
Original Assignee
Motorola Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Inc filed Critical Motorola Inc
Priority to AU2003205682A priority Critical patent/AU2003205682A1/en
Publication of WO2003086009A1 publication Critical patent/WO2003086009A1/fr

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Classifications

    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
    • H04R2201/401—2D or 3D arrays of transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
    • H04R2201/403—Linear arrays of transducers

Definitions

  • This invention relates to microphones for sound (e.g., speech) reception.
  • arrays of microphones whose output signals are processed and then combined into a single output signal, can enhance sound received from one particular source location (or direction) , relative to sounds from other locations (or directions) .
  • An important application is speech reception in noisy and/or reverberant environments, when it is not feasible to position a microphone very close to the talker's mouth. For example, hands-free telephones in cars and palmtop computers, held at arm's length, can receive speech more clearly by using arrays rather than single microphones.
  • the spatial response pattern of an array which makes it sensitive to sound from the desired source location but insensitive to sound coming from other locations, depends on the spatial layout of its microphones. Hence, when the locations of the sound sources change, the microphone layout would ideally be adjusted too, so as to maintain the optimal spatial response. Significant motion of the speech and noise sound sources relative to the array's platform is likely in many applications (e.g., hand-held devices, when the user moves his/her head or hand) . However, moveable microphones, which automatically changed their layout within their platform, would clearly be too costly and bulky for most applications.
  • the spatial response pattern of a delay-and-sum array can be made to track a moving source by adjusting the delays on the microphones' outputs.
  • the spatial response is highly constrained by the microphone layout. For example, to obtain a highly directional response with a compact array, the microphones must be placed along a line roughly parallel to the desired source direction.
  • a compact array is one whose inter-microphone distances are much smaller than the sound wavelengths they receive. This is the only kind of array that will fit into many small devices, such as hand-held devices. Hence, a compact array whose microphones moved in response to relative motion of the sound sources would have many potential applications.
  • An array's microphones may effectively be moved by switching its input channels between microphones fixed at different locations. Such switching of microphone output signals may be achieved in various known ways. Normally, microphone arrays employ digital signal processing, as this is much more flexible than analogue signal processing, and allows better adaptation to changing acoustic conditions. In such a "fully digitally processed" microphone array, the analogue output signal from each microphone is passed through an analogue-to- digital converter (ADC) and then a digital signal processor (DSP) , and the processed signals are then summed to give the array's output.
  • ADC analogue-to- digital converter
  • DSP digital signal processor
  • a performance evaluator continually measures the array's output signal quality (e.g., its Signal/Noise Ratio - S R) , and this performance measure is then fed back to an adaptation processor, which adjusts the digital signal processors so as to optimise performance.
  • the array adapts to changing acoustic conditions.
  • the microphone layout in such a "fully digitally processed" array could effectively be varied by varying the overall gains of the DSP channels (for example, a two-microphone array would be obtained when the adaptation processor set the gains in all but two channels to zero) . By changing the pair of channels that remains active, the array's alignment could effectively be rotated.
  • Arrays of this kind are known from U.S. Patent 5,715,319. Appended Figure 1 illustrates a typical example.
  • the more microphones there are in an array the more different layouts may be created by selecting subsets of the microphones. This can allow the array layout to be brought closer to the ideal layout for any given acoustic conditions.
  • the cost, the physical dimensions and the power consumption of the array also rise with the number of microphones, and the number of ADC's and DSP's associated with them.
  • the digital processing circuitry accounts for a large fraction of the cost and power consumption of a microphone array.
  • the digital processing circuitry also accounts for a large part of the array's physical size. This is especially true when the microphones are micro electromechanical (MEMS) devices, all integrated onto one silicon chip. Using such MEMS technology, it is possible to create a compact array that can be adopted into a very wide range of layouts, because it has a very large number of very small microphones.
  • MEMS micro electromechanical
  • One way to reduce the cost, size and power of the digital circuitry is to replace discrete components with a reduced number of integrated circuits.
  • FIG. 1 Another known way of decreasing the cost and size of the processing circuitry is to use multiplexing (i.e., processing multiple channels one after another in the same circuit) .
  • multiplexing requires faster digital circuitry, and there is a limit to the number of microphones that can be multiplexed into a single ADC or DSP.
  • Appended Figure 2 illustrates a typical example.
  • the first part of the alternative technique is to initially process the microphone outputs in analogue circuitry, so as to generate a reduced number of analogue signals.
  • the second part of the alternative technique digitises and further processes the reduced number of analogue signals.
  • This approach requires less and/or slower digital circuitry. Additional analogue pre-processing circuitry is required, but provided this is relatively simple, it can have lower cost, size and power consumption than the digital circuits it replaces.
  • Appended Figure 3 illustrates a typical example .
  • each microphone output is passed through a fixed analogue filter, certain sets of the filtered signals are then summed, and the resultant reduced number of signals is then digitised and processed further.
  • the filters on a summed set of microphones each have a different pass band, effectively creating a virtual microphone whose effective location varies with sound frequency.
  • this type of analogue pre-processed array has a fixed set of microphones connected to each of its DSP channels, which limits the range of microphone layouts it can achieve.
  • a switched-geometry arrangement for processing outputs from a plurality of microphones, as claimed in claim 1.
  • FIG. 1 is a block-schematic diagram illustrating a known "fully digitally processed" microphone array arrangement
  • FIG. 2 is a block-schematic diagram illustrating a known multiplexed digitally processed microphone array arrangement
  • FIG. 3 is a block-schematic diagram illustrating a known analogue pre-processed microphone array arrangement
  • FIG. 4 is a block-schematic diagram illustrating a generic switched-geometry microphone array arrangement incorporating the invention.
  • FIG. 5 is a block-schematic diagram illustrating a preferred embodiment of a switched-geometry microphone array arrangement, based on that shown in FIG. 1, incorporating the invention.
  • a "fully digitally processed" microphone array employs digital signal processing, as this is much more flexible than analogue signal processing, and allows better adaptation to changing acoustic conditions.
  • FIG. 1 in a conventional microphone array of this type the analogue output signal from each microphone (10.1- 10.7) is passed through an analogue-to-digital converter (13.1-13.7) and then a digital signal processor (14.1-
  • the processed signals are then summed at an adder (15) to give the array's output 0.
  • a performance evaluator (16) continually measures the array's output signal quality (e.g. its Signal/Noise Ratio - SNR) . This performance measure is then fed back to an adaptation processor (17) , which adjusts the digital signal processors (14.1-14.7) so as to optimise performance. By this means, the array adapts to changing acoustic conditions .
  • the microphone layout in such a "fully digitally processed" array could effectively be varied by varying the overall gains of the DSP channels.
  • a two-microphone array would be obtained when the adaptation processor set the gains in all but two channels to zero, as illustrated in FIG. 1.
  • the array's alignment (19) could effectively be rotated. It will be appreciated that, as illustrated, the arrow 19 shows array alignment with only DSP's 14.3 and 14.7 active.
  • the more microphones there are in an array the more different layouts may be created by selecting subsets of the microphones. This can allow the array layout to be brought closer to the ideal layout for any given acoustic conditions.
  • the cost, the physical dimensions and the power consumption of the array also rise with the number of microphones, and the number of analogue-to-digital converters (ADC's) and digital signal processors (DSP's) associated with them.
  • the digital processing circuitry typically accounts for a large fraction of the cost and power consumption of a microphone array.
  • the digital processing circuitry In a compact array, whose microphones are clustered within a small volume, the digital processing circuitry typically also accounts for a large part of the array's physical size. This is especially true when the microphones are micro electromechanical (MEMS) devices, all integrated onto one silicon chip. Using such MEMS technology, it is possible to create a compact array that can adopt a very wide range of layouts, because it has a very large number of very small microphones. It is thus desirable to reduce the amount of digital processing circuitry used by an array, without reducing its number of microphones, which would limit the range of microphone layouts it could adopt.
  • One way to reduce the cost, size and power of the digital circuitry is by replacing discrete components with a reduced number of integrated circuits.
  • Another known way of decreasing the cost and size of the processing circuitry is to use multiplexing, i.e., processing multiple channels one after another in the same circuit .
  • the multiplexer (21) connects the output of each microphone (20.1-20.7) in turn to a single ADC (23).
  • the ADC and the DSP (24) process the latest signal samples from each microphone one after another, before combining them to generate the latest array output signal sample.
  • multiplexing requires faster digital circuitry, and there is a limit to the number of microphones that can be multiplexed into a single ADC or DSP.
  • each microphone output (30.1-30.7) is passed through a fixed analogue filter (31.1-31.7), and certain sets of the filtered signals are then summed at adders (32.1-32.3) .
  • the resultant reduced number of signals is then digitised by ADC's (33.1-33.3) and processed further.
  • ADC's 33.1-33.3
  • the filters on a summed set of microphones each have a different pass band, the effect of which is to create a virtual microphone whose effective location varies with sound frequency.
  • this type of analogue pre- processed array has a fixed set of microphones connected to each of its DSP channels, which limits the range of microphone layouts it can achieve.
  • each of M microphones (40.1-40.M) in an array passes its output signal to a respective analogue switch (41.1-41.M).
  • Each switch passes its input signal to one of N outputs (N ⁇ M) , or does not pass it on (it will be appreciated that the lowest output line from each of the switches represents no output from that switch, i.e., switching off the switch' s respective microphone) .
  • the array signal processor processes and combines its N input signals so as to generate the array's final output O.
  • the analogue switches (41.1-41.M) By adjusting the analogue switches (41.1-41.M) , the combination of microphone outputs that is passed to each input of the array signal processor (43) may be varied. Just one microphone at a time could be connected to each signal-processor input, leaving M-N microphones unused. Alternatively, more than one microphone could be connected to some or all of the signal processor inputs .
  • the signal on each signal processor input is the sum of the output signals of all the microphones connected to it.
  • an analogue pre-processor (51) includes switches and adders, and an array signal processor (53) comprises three ADC's (53.1- 53.3), each feeding a respective DSP (54.1-54.3), whose outputs are summed at an adder (55) to give the array's final output O.
  • a performance evaluator (56) continually measures the array's output signal quality. This performance measure is then fed back to an adaptation processor (57) , which adjusts the digital processors (54.1-54.3) and the switches within the analogue preprocessor (51) so as to continually optimise performance.
  • the switches within the analogue pre-processor (51) divide these microphones into three sets (50.1 & 50.3; 50.2, 50.4 & 50.6; and 50.5 & 50.7) and the adders within the analogue pre-processor (51) sum the outputs of each set.
  • the three summed signals are then fed to the ADC's (53.1- 53.3) .
  • the effect of summing a set of microphone outputs is to create a single virtual microphone, located at the centroid of the real microphones. This embodiment thus creates an array of three virtual microphones, aligned as shown by the arrow (59) .
  • the arrow 59 shows array alignment with microphones switched to array processor inputs as follows: microphones 50.1 and 50.3 switched to input 1; microphones 50.2, 50.4 and 50.6 switched to input 2; and microphones 50.5 and 50.7 switched to input 3.
  • the effective layout of the array may be varied by changing the sets of microphones that are summed together on each ADC input .
  • the advantage of adaptive control is that the array's output signal quality is kept high despite changing acoustic conditions.
  • the array's spatial response pattern may be adjusted to track moving sound sources .
  • microphone intrinsic noise is a significant problem in very small microphones, such as MEMS microphones, so adding the outputs of many adjacent MEMS microphones can improve array performance.
  • fixed analogue filters may additionally be included.
  • Such fixed analogue filters filter microphone output signals before they are fed to the analogue adders.
  • filters with different frequency responses are applied to the inputs to an adder, the location and sensitivity of the resultant virtual microphone varies with frequency. This allows the effective configuration of microphones connected to the array processor to vary with frequency, which gives greater flexibility to optimise array performance over a range of frequencies.
  • the array processor (43) may use analogue or digital signal processing, which may be fixed or adaptive, as appropriate to the application.
  • a microphone array with the same performance as any embodiment of this invention could be realised by passing each microphone output straight to an ADC, and performing all additions and other signal processing in digital circuitry.
  • the simple analogue switches and adders used in the embodiments of the invention described above will have lower cost, size and power consumption than their digital alternative.
  • This invention may be most advantageous when a large number of microphones (-fifty or more) is connected to a much smaller number of array signal processor inputs, and especially when the analogue switches and adders are integrated into a silicon chip along with the microphones .
  • each microphone has a similar set of switches and adders on its output, this set could be placed next to each microphone, to form a "microphone block".
  • a regular array of any size could then be built up by connecting identical blocks together.
  • This block-based structure is particularly suited to arrays integrated into a single silicon chip.
  • This invention facilitates summing the outputs of a large number of adjacent microphones to provide each input to an array signal processor, rather than having just one microphone on each input .
  • the main advantage of summing the outputs of a large number of adjacent microphones is that microphone intrinsic noise is reduced, relative to sound signals. Since the microphones are close together, their sound signals are very similar, and add coherently, whereas their intrinsic noise signals are incoherent.
  • the microphones In a compact array of a large number of small MEMS microphones, the microphones generally have high intrinsic noise levels. Furthermore, because compact arrays are not very sensitive to low-frequency sound, their low-frequency performance is degraded by high levels of microphone intrinsic noise. Summing the outputs of a large number of adjacent microphones is thus especially beneficial for compact MEMS arrays. It will be understood that although the invention derives particular benefit when the microphones such as MEMS are fabricated with the switching and processing circuitry (e.g., in a single integrated circuit), the switching and processing circuitry may of course be fabricated separately from the microphones and connected subsequently thereto.

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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'invention concerne un agencement à géométrie commutée, ainsi qu'un procédé de traitement des sorties de microphones (40.1 40.M) par : réception de signaux provenant des microphones à des entrées respectives ; commutation (41.1 41.M) des signaux reçus aux entrées, entre des sorties ; sommation (42.2.1 42.M.N) de quelques-unes, désirées, des sorties, et traitement du réseau (43) de manière à produire un signal de sortie à géométrie commutée. Le fonctionnement des commutateurs altère la configuration des microphones connectés au processeur du réseau (43), et la commutation et le traitement subséquent peuvent s'opérer de manière adaptative en fonction du signal de sortie. La commutation dans des circuits analogiques avec traitement subséquent effectué numériquement permet d'obtenir des coûts et des dimensions et une consommation d'énergie plus faibles que dans le cas d'un traitement entièrement numérique. Les résultats les plus avantageux sont obtenus lorsqu'un grand nombre de microphones (à savoir, 50 ou plus) sont connectés à un nombre, beaucoup plus faible, d'entrées de processeurs de signaux de réseau et, en particulier, lorsque les commutateurs analogiques et les circuits d'addition sont intégrés dans une puce de silicium, conjointement avec un réseau de microphones ( par exemple, dispositif MEMS).
PCT/EP2003/000789 2002-04-10 2003-01-27 Agencement de reseaux de microphones a geometrie commutee, et procede de traitement de sorties d'une pluralite de microphones WO2003086009A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003205682A AU2003205682A1 (en) 2002-04-10 2003-01-27 Switched-geometry microphone array arrangement and method for processing outputs from a plurality of microphones

Applications Claiming Priority (2)

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GB0208219.6 2002-04-10
GB0208219A GB2387499B (en) 2002-04-10 2002-04-10 Switched-geometry microphone array arrangement and method

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1906704A1 (fr) * 2006-09-26 2008-04-02 Sonion A/S Microphone micro-électromécanique étalonné
US20120140949A1 (en) * 2010-12-03 2012-06-07 Chen L T Conference system for independently adjusting audio parameters
US8923529B2 (en) 2008-08-29 2014-12-30 Biamp Systems Corporation Microphone array system and method for sound acquisition

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8041054B2 (en) * 2008-10-31 2011-10-18 Continental Automotive Systems, Inc. Systems and methods for selectively switching between multiple microphones
US11290814B1 (en) * 2020-12-15 2022-03-29 Valeo North America, Inc. Method, apparatus, and computer-readable storage medium for modulating an audio output of a microphone array

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Publication number Priority date Publication date Assignee Title
DE3007585A1 (de) * 1980-02-28 1981-09-03 Polygram Gmbh, 2000 Hamburg Anordnung zur schallaufnahme und -wiedergabe
JPS5952996A (ja) * 1982-09-20 1984-03-27 Nippon Telegr & Teleph Corp <Ntt> 可変指向性音響装置
US5828768A (en) * 1994-05-11 1998-10-27 Noise Cancellation Technologies, Inc. Multimedia personal computer with active noise reduction and piezo speakers
US5848170A (en) * 1995-12-22 1998-12-08 France Telecom Acoustic antenna for computer workstation

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Publication number Priority date Publication date Assignee Title
DE3007585A1 (de) * 1980-02-28 1981-09-03 Polygram Gmbh, 2000 Hamburg Anordnung zur schallaufnahme und -wiedergabe
JPS5952996A (ja) * 1982-09-20 1984-03-27 Nippon Telegr & Teleph Corp <Ntt> 可変指向性音響装置
US5828768A (en) * 1994-05-11 1998-10-27 Noise Cancellation Technologies, Inc. Multimedia personal computer with active noise reduction and piezo speakers
US5848170A (en) * 1995-12-22 1998-12-08 France Telecom Acoustic antenna for computer workstation

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1906704A1 (fr) * 2006-09-26 2008-04-02 Sonion A/S Microphone micro-électromécanique étalonné
US8036401B2 (en) 2006-09-26 2011-10-11 Epcos Pte Ltd Calibrated microelectromechanical microphone
US8923529B2 (en) 2008-08-29 2014-12-30 Biamp Systems Corporation Microphone array system and method for sound acquisition
US9462380B2 (en) 2008-08-29 2016-10-04 Biamp Systems Corporation Microphone array system and a method for sound acquisition
US20120140949A1 (en) * 2010-12-03 2012-06-07 Chen L T Conference system for independently adjusting audio parameters

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GB2387499A (en) 2003-10-15
GB0208219D0 (en) 2002-05-22
GB2387499B (en) 2004-05-26
AU2003205682A1 (en) 2003-10-20

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