US20030108208A1 - Method and device for comparing signals to control transducers and transducer control system - Google Patents

Method and device for comparing signals to control transducers and transducer control system Download PDF

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Publication number
US20030108208A1
US20030108208A1 US10/203,856 US20385602A US2003108208A1 US 20030108208 A1 US20030108208 A1 US 20030108208A1 US 20385602 A US20385602 A US 20385602A US 2003108208 A1 US2003108208 A1 US 2003108208A1
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Prior art keywords
sound
information
pieces
speaker
microphone
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Abandoned
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US10/203,856
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English (en)
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Jean-Philippe Thomas
Marc Emerit
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Orange SA
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France Telecom SA
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Publication of US20030108208A1 publication Critical patent/US20030108208A1/en
Assigned to FRANCE TELECOM SA reassignment FRANCE TELECOM SA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: EMERIT, MARC, THOMAS, JEAN-PHILIPPE
Priority to US11/755,563 priority Critical patent/US7804963B2/en
Abandoned legal-status Critical Current

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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
    • H04R27/00—Public address systems

Definitions

  • the invention relates to a method for the automatic comparison of information characterizing reference values and information characterizing current values of sound-reproducing systems of a system of microphones and speakers for the control of the sound-reproducing system.
  • the field of the invention is that of the automatic control of the gains, functioning and position of several microphones and several speakers in the context of a system of videoconferencing between participants located at distinct sites that are generally remote sites.
  • the invention can also be applied to the control of microphones and speakers installed in the same room such as a theatre stage, concert hall or cinema hall. It can be used to control the spatialized sound rendition of the scene which provides concordance between visual images and sound.
  • the invention makes it possible to approach a natural communications situation: when a participant changes position in a remote room during a meeting, the sound follows him in the room in which he is being listened to, with a passage, for example, from one speaker to another as he moves.
  • the microphones and speakers are designated, without distinction, by the term transducers.
  • the problem is to detect the changes that occur at the transducers between their installation and the times at which the checks are made.
  • An object of the present invention therefore is a method of comparison between pieces of information characterizing reference values and pieces of information characterizing current values of sound-reproducing systems of a system of (n) microphones m i and (p) speakers hp j for the control of said sound-reproducing systems characterized in that:
  • At least one sound signal S is sent on the speaker hp j .
  • D the matrices Q and Q r are compared.
  • An object of the invention is also a device for comparing pieces of information characterizing reference values and pieces of information characterizing current values of sound-reproducing systems of a system of n microphones m i and p speakers hp j for the control of the sound-reproducing system, characterized in that the control system comprises means for the measurement of the pieces of information hp j m i characterizing the sound-reproducing systems comprising a microphone m i and a speaker hp j , digital processing means to compare said pieces of information hp j m i and, connected to these digital processing means, means for saving the matrix Q r constituted by all the pieces of information hp j m i .
  • An object of the invention is also a system for the control of sound-reproducing systems comprising several devices such as those mentioned here above, characterized in that the devices are distributed among several rooms and in that the control system comprises a high bit-rate telecommunications network connecting said rooms and means to centralize the management of the devices.
  • FIG. 1 a is a diagrammatic view of a videoconferencing room according to the invention
  • FIG. 1 b is a diagrammatic view of the direct paths between speakers and microphones
  • FIGS. 2 a ) and 2 b ) are views of sound-reproducing systems respectively in the case of local processing and when the processing is done in the network,
  • FIGS. 3 a ) and 3 b ) respectively show examples of curves representing white noise and USASI noise on the one hand and pink noise and pseudo-random binary sequences on the other hand,
  • FIG. 4 shows the impulse response of a microphone following the sending, by a speaker, of a pseudo-random binary sequence
  • FIG. 5 is a diagrammatic view of the configuration of the signal digital processing card
  • FIG. 6 is a diagrammatic view of the system of microphones and speakers distributed among several rooms connected to one another by a multipoint bridge.
  • a videoconference is set up between participants distributed among several rooms, a high-bit-rate communications network such as an ATM network being used to convey visual and sound information.
  • a videoconferencing room shown FIG. 1 a is provided with a display screen E, several microphones m i and several speakers hp j providing for a spatialized rendition of the audiovisual scene of the remote room or rooms.
  • the speakers may be located, without distinction, all below the screen, all on top or distributed as shown in FIG. 1 a, or even in any other arrangement.
  • the videoconferencing room used for the invention is provided with six microphones and six speakers, the distance between microphones and speakers ranging typically from three to five meters.
  • the sound-reproducing systems between the microphones m i and the speakers hp j of a local processing system comprise the microphones m i , the microphone preamplifiers am i , the analog-digital converters ADC i , the digital processing card, the digital-analog converters DAN j , the amplifiers of the speakers ahp j , the speakers hp j and the room.
  • the sound-reproducing systems between the microphones m i and the speakers hp j of a remote processing system shown in FIG. 2 b comprise the microphones m i , the microphone preamplifiers am i , the analog-digital converters ADC i , the encoders C i , the transportation network R, the decoder D, the digital processing card, the encoder C, the transportation network R, the decoders D j , the digital-analog converters DAN j , the amplifiers of the speakers ahp j , the speakers hp j and the room.
  • a routing system A obtained by a multiplexer/demultiplexer also called a switching matrix, which is commercially available, may be inserted if necessary into the sound-reproducing systems between, firstly, the analog-digital converters ADC i and the encoders C i and, secondly, the decoders D j and the analog-digital converters ADC j .
  • a remotely controllable system A of this kind makes it possible, at this level of the sound-reproducing system, to route the information characterizing a transducer from one transducer to another.
  • Each element of these sound-reproducing systems must be adjusted so as to provide for efficient sound transmission.
  • the gains, wirings and positions of the transducers of each room are set, and these parameters are stored in a file of a digital processing card of the signal.
  • transducer (speaker or microphone respectively) will designate the transducer (the speaker or microphone respectively) and the elements of the sound-reproducing system between the digital processing card and the transducer (speaker or microphone respectively).
  • the transducers may have been moved and in certain cases may have become defective; the room configuration may have been changed; the amplifiers also may have been subjected to high variations over time, possibly caused by the heating of the electronic components. It may be preferred sometimes to act on the transducers in order to compensate for a defect in another element of the sound-reproducing system.
  • the term “sound signal” refers to a signal that can be sent by the speakers and detected by the microphones. As indicated in FIGS. 2 a ) and 2 b ), a sound signal S is sent to all the p speakers hp j , one after the other at t 1 , . . . , t j , . . . , t p , each in turn, and retrieved at the n microphones m i .
  • the reference hp j m i is given to the piece of information characterizing the sound-reproducing system comprising the speaker hp j and the microphone m i .
  • All these hp j m i pieces of information constitute a matrix with a size n*p, a line of the matrix corresponding to a speaker and a column corresponding to a microphone.
  • this matrix is constituted after the alignment, or at another preferred time, it is saved in memory: it is called the reference matrix Q r , the elements hp j m i of this matrix being reference values. Thereafter, when a check has to be made on the parameters of these transducers, these steps are reiterated with a signal S′ to obtain current values hp j m i and set up a matrix Q that is compared with the matrix Q r .
  • the elements hp j m i are set up from signals S and S′ considered in the time domain, but it is possible to base the operation on the frequency domain and set up the matrices Q and/or Q r from the spectral responses hp j m i of the microphones m i at a frequency band sent by the speakers hp j : whatever the width of the frequency band of the signals S and S′ sent by the speakers hp j , only a determined frequency band will be received by the microphones m i . It could be a frequency band with a width of about 200 Hz, an octave band or a one-third-octave band. This frequency band will then be made in order to slide to sweep through a spectrum of 0 Hz to 1000 Hz for example.
  • each transducer is verified, i.e. it is verified that all the frequencies pass through each transducer. If one of them has irregularities, the necessary corrections are made.
  • the microphones sometimes have irregularities related to the table or room effect (to the reflections from the table or room), where the wave reflected by the table or room may be in phase opposition with the direct wave, then giving rise to black regions in the spectral response: the gain of the microphone will then be increased in the corresponding frequency band.
  • the spectral responses of the transducers by frequency band will be verified.
  • the comparison between the matrices Q and Q r makes it possible, especially, to obtain a piece of information on any movement undergone by the transducers, these transducers being directional and their directivity depending on the frequency.
  • the exploitation of the results is sometimes more complex than it is when the operation is situated in the time domain.
  • the sound signals S and S′ are generally recorded in the internal memory of the signal digital processing card. They may possibly be computed (generated) in this card.
  • These sound signals may, for example, be a white noise, a pink noise, an USASI noise, a pseudo-random binary sequence respectively shown in FIGS. 3 a ) and 3 b ) or a sine frequency sweep, an octave-filtered noise or one-third-octave filtered noise, or again another sound signal.
  • a pseudo-random binary sequence is purely deterministic; it is a sequence of 1 and ⁇ 1 with a length N. The characteristic feature of these sequences is that their correlation function is equal to N for 0 and to ⁇ 1 for other values. This correlation function is therefore very close to a Dirac distribution.
  • the method according to the invention has been carried out with a pink noise sent successively to each of the speakers for one second. Between two sending operations on two consecutive speakers, there is a wait for a certain time (a period of silence) for the next sound signal to start in a state of the sound-reproducing system that is, in principle, a stable state.
  • the invention has been achieved with a two-second period of silence.
  • the elements hp j m i are determined for each hp j at the same instant t of the sound signal. If, for example, hp 1 m 1 , hp 1 m 2 , . . .
  • this divergence is contained in a predetermined range referenced FHP for the speakers and FM for the microphones, then no correction is applied as the difference is tolerable.
  • a threshold of 3 dB is, for example, commonly accepted for a visioconference room.
  • a corresponding divergence is applied as a corrective value to the transducer, at the signal digital processing card.
  • the correction could be applied to the gain of the transducer itself. In certain cases, the correction will consist in repositioning the transducer; in other cases, it will not be possible to apply the correction because of a transducer malfunction, and the defective transducer will then be changed.
  • the characteristics of the pseudo-random binary sequences make them a preferred signal for the high-precision measurement of the impulse response of a system according to the invention.
  • the use of a pseudo-random binary sequence as a sound signal sent to the speakers hp j therefore enables the measurement of the impulse responses, as a function of time R ji , of all the microphones m i .
  • each impulse response R ji gives information on the delay, namely, the propagation time between a speaker hp j and a microphone m i , the direct wave corresponding to the direct paths between a speaker hp j and microphone m i , or again the room effect corresponding to the paths with one or more reflections.
  • t 0j denotes the instant at which the sound signal is sent from a speaker hp j
  • t 1ji is the instant at which the microphone m i receives the direct wave
  • t 2ji is the instant at which the room effect starts for the microphone m i . It is possible to measure the delays to verify the respective position of the transducers themselves.
  • the matrix Q r is computed by measuring the delays (hp j m i ) Qr for a first time.
  • the position of the transducers is deduced from these delays by triangulation: if, for example, with the position of hp 1 and hp j being known, the delays (hp 1 m 1 ) Qr and (hp j m 1 ) Qr are considered, the position of the microphone m 1 when the reference matrix is set up is deduced from this. The same procedure is used for the other microphones. The same reasoning can be applied to determining the position of the speakers from those of the microphones.
  • the delays (hp j m i ) Q of the matrix Q are subsequently computed, the transducer that has changed position will subsequently by identified by comparison with the delays of the matrix Q r .
  • a correction is applied to the transducer, at the signal digital processing card, to compensate for the change in position. In other cases, the correction will consist in repositioning the transducer itself.
  • each element hp j m i of the matrices Q and Q r will represent the part of the impulse response that succeeds the first spike and starts at t 2ji .
  • the signal-to-noise ratio of the microphones m i is evaluated by comparing the mean values of the microphones computed from the matrix Q r , set up in considering a sound signal S, with the mean values of the microphones computed from the matrix Q set up in considering a signal S′ of silence.
  • the signal S may be, especially, a white, rose or USASI noise, or a pseudo-random binary sequence. If the signal S is interspersed with silences, in practice, the signal-to-noise ratio will be measured during a phase of silence.
  • the information processing comprises especially the measurements, computations, saving operations and corrections to be made.
  • Remote processing can be done by a computer remotely controlling another computer, located in a local room, through the network.
  • An echo phenomenon sometimes occurs: when a participant speaks in a room A, the corresponding sound signal is transmitted to the participants located in a room B by the speakers of this room B, the microphones of this room B taking up the signal coming from these speakers and sending them on to the room A. The speaker of the room A hears himself again with the echo. This echo can be evaluated by measuring the level of the return signal with respect to the level of the signal sent. The control parameters of the echo cancellation or transducer gain variation algorithms are then adjusted.
  • Each room Sa may be connected to the bridge PMP by one or more transmission channels k.
  • two channels could be used for a room to obtain a stereophonic rendition or four could be used to obtain a quadraphonic rendition.
  • r k for example will designate the sound-reproducing system comprising a transmission channel k transmitting from the room to which it is connected to the bridge PMP and e k′ will designate the sound-reproducing system comprising a transmission channel k′ transmitting from the bridge PMP to the room to which it is connected, where k can be equal to k′.
  • the elements hp j m i will then be replaced by r k e k′ .
  • the device comprises a signal digital processing card CTN, shown in FIG. 5.
  • This card comprises means Mes for the measurement of the information hp j m i , processing means T and file-saving means SF such as an internal memory in which one or more sound signals are recorded.
  • This sound signal may also be computed by the processing means T.
  • the matrix elements hp j m i of the matrix or matrices Q r and, possibly, one of more matrices Q are also saved in the internal memory, along with the parameters of the various elements of each of the sound-reproducing systems obtained during the setting of the room or rooms.
  • the processing means are used to compare elements hp j m i or combinations of these elements belonging to a same matrix Q or to several matrices. They can also be used to compute the corrections to be made to one or more elements of the sound-reproducing system and apply them. They could, for example, correct the gain of a speaker hp j and/or a microphone m i . They also enable the generation of a sound signal.
  • These processing means T will be made conventionally by means of a microprocessor P and an associated program memory M comprising a program capable of carrying out the measurements, comparisons, computations and corrections to be made.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Stereophonic System (AREA)
  • Selective Calling Equipment (AREA)
  • Analogue/Digital Conversion (AREA)
US10/203,856 2000-02-17 2001-02-15 Method and device for comparing signals to control transducers and transducer control system Abandoned US20030108208A1 (en)

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FR00/01976 2000-02-17
FR0001976A FR2805433A1 (fr) 2000-02-17 2000-02-17 Procede et dispositif de comparaison de signaux pour le controle de transducteurs et systeme de controle de transducteurs

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EP (1) EP1258168B1 (fr)
JP (1) JP4691304B2 (fr)
AT (1) ATE505911T1 (fr)
AU (1) AU2001235692A1 (fr)
DE (1) DE60144420D1 (fr)
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US20080284409A1 (en) * 2005-09-07 2008-11-20 Biloop Tecnologic, S.L. Signal Recognition Method With a Low-Cost Microcontroller
EP2715305A4 (fr) * 2011-05-27 2015-09-30 Underwood Marcos Système, commandes et procédé d'essai acoustique à champ direct
EP2771682A4 (fr) * 2011-10-27 2015-10-21 Paul Larkin Répartition de signaux d'excitation pour essais acoustiques en champ direct
EP3069117A4 (fr) * 2013-11-15 2017-06-07 Msi Dfat Llc Réduction des ondes stationnaires lors d'essais acoustiques en champ direct

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US8208645B2 (en) * 2006-09-15 2012-06-26 Hewlett-Packard Development Company, L.P. System and method for harmonizing calibration of audio between networked conference rooms
EP2499504B1 (fr) * 2009-11-12 2021-07-21 Digital Harmonic LLC Mesure de précision de formes d'onde à l'aide d'une déconvolution et d'un fenêtrage
US8620976B2 (en) 2009-11-12 2013-12-31 Paul Reed Smith Guitars Limited Partnership Precision measurement of waveforms
WO2011060130A1 (fr) * 2009-11-12 2011-05-19 Paul Reed Smith Guitars Limited Partnership Identification et séparation de domaines pour mesure précise de formes d'ondes
US8873821B2 (en) 2012-03-20 2014-10-28 Paul Reed Smith Guitars Limited Partnership Scoring and adjusting pixels based on neighborhood relationships for revealing data in images
US9596553B2 (en) * 2013-07-18 2017-03-14 Harman International Industries, Inc. Apparatus and method for performing an audio measurement sweep
JP6518530B2 (ja) * 2015-06-26 2019-05-22 京セラ株式会社 電子機器
US10306129B1 (en) * 2016-06-28 2019-05-28 Amazon Technologies, Inc. Local and remote video-camera control
US9837064B1 (en) 2016-07-08 2017-12-05 Cisco Technology, Inc. Generating spectrally shaped sound signal based on sensitivity of human hearing and background noise level

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Publication number Priority date Publication date Assignee Title
US20080284409A1 (en) * 2005-09-07 2008-11-20 Biloop Tecnologic, S.L. Signal Recognition Method With a Low-Cost Microcontroller
EP2715305A4 (fr) * 2011-05-27 2015-09-30 Underwood Marcos Système, commandes et procédé d'essai acoustique à champ direct
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EP2771682A4 (fr) * 2011-10-27 2015-10-21 Paul Larkin Répartition de signaux d'excitation pour essais acoustiques en champ direct
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JP4691304B2 (ja) 2011-06-01
ATE505911T1 (de) 2011-04-15
FR2805433A1 (fr) 2001-08-24
JP2003523674A (ja) 2003-08-05
EP1258168B1 (fr) 2011-04-13
AU2001235692A1 (en) 2001-08-27
EP1258168A1 (fr) 2002-11-20
US7804963B2 (en) 2010-09-28
DE60144420D1 (de) 2011-05-26
US20070286430A1 (en) 2007-12-13
WO2001062044A1 (fr) 2001-08-23

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