Classifications

• • 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
  • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R29/00—Monitoring arrangements; Testing arrangements
  • H04R29/001—Monitoring arrangements; Testing arrangements for loudspeakers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R29/00—Monitoring arrangements; Testing arrangements
  • H04R29/004—Monitoring arrangements; Testing arrangements for 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
  • H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
  • H04R2201/028—Structural combinations of loudspeakers with built-in power amplifiers, e.g. in the same acoustic enclosure

Definitions

• the present application relates to a device and method for calibrating microphones in an electronic system, including a sound pickup system.
• Some electronic systems including sound recording systems, may include a plurality of microphones, particularly for improving the quality of the recorded acoustic information and / or extracting information about sound sources and / or surroundings.
• FIG. 1 represents, partly and schematically, an exemplary sound pickup system 10 comprising a plurality of microphones 12 which are distributed over the site 14 on which sound recording is performed.
• the microphones 12 are connected to an audio signal processing device 16.
• the microphones 12 transmit to the processing device 16 analog or digital electrical signals resulting from the conversion of the sound waves, and the processing device 16 applies a processing to the audio signals digital from signals provided by the microphones, and for example produces and stores digital audio files.
• the processing device 16 When processing the signals provided by the microphones 12, the processing device 16 generally operates by default as if the properties of the microphones 12 were identical.
• An example of a property is the time that elapses between the moment of reception of a sound wave by the microphone 12 and the moment at which the processing device 16 begins to perform a processing on the digital audio signal obtained by analog conversion / digital signal picked up by the microphone 12. This delay is called transmission delay thereafter.
• Other examples of microphone properties are phase shift and gain when converting the sound signal.
• the properties of the microphones 12 are generally not identical.
• the transmission delays associated with the microphones are generally not identical and must be taken into account when generating the audio files by the processing device 16, so that, when these audio files are listened to, a suitable sound reproduction is obtained. Transmission delays differ especially between analog microphones and digital microphones.
• An analog microphone transmits to the processing device an analog signal representative of the sound waves received by the microphone and the processing device performs the analog / digital conversion of this analog signal.
• An analog microphone is generally connected to the processing device by a wired link so that the duration of the analog signal transfer from the analog microphone to the processing device is negligible.
• a digital microphone includes a digital-to-analog converter that converts the analog signal from the conversion of the sound signal into a digital signal transmitted to the processing device.
• the transmission of the digital or analog microphone signals to the processing device 16 may be a wireless transmission using electromagnetic waves.
• the transmission delay of the microphone then includes, in addition, the delay for the transmission and reception of electromagnetic waves but also the delay for possible encoding and error correction processing by the transmitter.
• FIG. 1 schematically shows four microphones 12 including three microphones 12 connected to the processing device 16 by a wire link 18 and a microphone 12 connected to the processing device 16 by a wireless link 20.
• the compensation of the differences between the transmission delays of the microphones 12 may include the addition by an operator of variable delays, stored by the processing device 16, so that the start times of recording of the audio files are identical.
• the compensation of the differences between the amplification ratios and the phase offsets of the microphones 12 may include the addition of a filter applied by the processing device 16 to the signals supplied by the microphones 12 so that the Recorded audio files correspond to the audio files that would be obtained if the amplification ratios and phase shifts of the microphones 12 were identical.
• An exemplary calibration method of the sound pickup system 10 comprises the emission by a sound generator 24, for example a loudspeaker, possibly controlled by the processing device 16, of several known sequences of sound signals and the analyzing the audio files provided by the processing device 16 following the acquisition of these sound signal sequences by the microphones 12.
• a sound generator 24 for example a loudspeaker, possibly controlled by the processing device 16, of several known sequences of sound signals and the analyzing the audio files provided by the processing device 16 following the acquisition of these sound signal sequences by the microphones 12.
• a disadvantage is that it can then be difficult from the analysis of the audio files to separate, for each microphone 12, the transmission delay associated with the microphone 12 of the propagation delay.
• An object of an embodiment is to provide a calibration device of a sound pickup system that overcomes all or part of the disadvantages of the devices described above.
• Another object of an embodiment is that the calibration can be performed automatically.
• Another object of an embodiment is that the calibration can be performed in a simple manner.
• Another object of an embodiment is that the calibration can be performed quickly.
• an embodiment provides a calibration device comprising a sound pickup system comprising microphones connected to an audio signal processing device, the calibration device further comprising an enclosure containing at least a portion of the processing device, a sound generator connected to the processing device, and a microphone holder adapted to hold the microphones at the same distance from the sound generator.
• the device further comprises an accumulator battery.
• the sound generator is located between the support and the processing device.
• the sound generator is in contact with the support.
• the support is at least partly made of an elastic material.
• the support comprises holes receiving the microphones, and at least one of the holes has a shape at least partially complementary to one of the microphones.
• the minimum distance separating each microphone from the sound generator is less than 20 cm.
• the number of microphones is greater than or equal to five.
• One embodiment also provides for the use of the calibration device as previously defined for the calibration of the microphones of the sound recording system.
• the use comprises the following steps:
• the use further comprises the step of adding, for at least one of the microphones, a delay by the processing device during subsequent acquisitions of digital audio signals representative of sound signals picked up by said microphone.
• FIG. 1 described above, partially and schematically shows an example of sound recording system
• Figures 2 and 3 are sectional views, partial and schematic, of an embodiment of a calibration device of a sound recording system
• Figure 4 is a partial sectional and schematic, similar to Figure 3 of another embodiment of a calibration device of a sound recording system
• Fig. 5 is a block diagram of one embodiment of a method of calibrating a sound recording system
• FIG. 6 represents an exemplary envelope of an audio signal emitted by a loudspeaker and the digital audio signals acquired by a processing device of the calibration device of FIG. 2 during the implementation of the method of FIG. calibration illustrated in Figure 5;
• Fig. 7 is a block diagram of a more detailed embodiment of a step of the calibration method illustrated in Fig. 5.
• the microphones for the calibration of microphones, it is intended to arrange the microphones near a loudspeaker in a fixed and known configuration. The relative position between each microphone and the speaker is then known beforehand. Preferably, the microphones are arranged so that the propagation delay of the sound waves from the loudspeaker to each microphone is substantially constant. Determining the transmission delays of the microphones is then facilitated.
• the terms "sound signal” and "acoustic signal” are used interchangeably.
• FIGS. 2 and 3 are sectional, partial and schematic views of an embodiment of a calibration device 30 of a sound recording system 31.
• the calibration device 30 comprises an enclosure 32 in which the elements of the sound recording system 31 are arranged, in particular a device for processing sound signals.
• the chamber 32 further contains a sound generator 36, for example a loudspeaker, preferably connected to the processing device 34 and controlled by the processing device 34.
• the loudspeaker 36 can be connected to the device treatment 34 by a wired link or be controlled by the processing device 34 by a wireless link, including implementing electromagnetic waves.
• the loudspeaker 36 is preferably located above the processing device 34.
• the processing device 34 corresponds, for example, to the product marketed by Aaton-Digital under the name Cantar-X3.
• the processing device 34 may comprise a dedicated electronic circuit and / or a processor, for example a microcontroller, adapted to execute the instructions of a computer program stored in a memory.
• the speaker 36 may be a broadband speaker.
• An electric storage battery 38 for the power supply of the treatment device 34 and / or the speaker 36 may be disposed in the enclosure 32.
• the battery 38 may be located between the treatment device 34 and the loudspeaker 34.
• the processor 34 may be located between the loudspeaker 36 and the battery 38.
• the loudspeaker 36 and / or the electric storage battery 38 may be integrated wholly or partly into the processing device 34.
• the pick-up system 31 further includes microphones 40 connected to the processing device 34.
• the number of microphones 40 may be between 2 and 50, preferably between 2 and 20.
• a processing device 34 connected to five microphones 40.
• Each microphone 40 may be connected to the processing device 34 by a wire link or a wireless link implementing the transmission of electromagnetic waves.
• FIG. 2 there are shown five microphones 40 including two microphones each of which is connected to the processing device 34 by a cable 42 and a microphone transmits signals to the processing device 34 via a wireless link, no represented.
• Each microphone 40 comprises a transducer adapted to receive an acoustic signal S (t) and to convert it into an analog electrical signal S e (t), also called analog audio signal, where t indicates a time variable.
• S (t) an acoustic signal
• S e (t) an analog electrical signal
• t indicates a time variable.
• Each microphone 40 has a transfer function H which, in the frequency domain, is given by the following relation (1):
• ⁇ ( ⁇ ) ⁇ ( ⁇ ) ⁇ ( ⁇ ( ⁇ )) (1)
• ⁇ the pulsation of the acoustic signal
• A the conversion gain that can depend on the frequency
• ⁇ the phase shift that can depend on the frequency
• the processing device 34 is adapted to determine, for each microphone 40, a digital audio signal S n from the analog audio signal S e (t).
• the microphone 40 can transmit the analog audio signal S e (t) to the processing device 34 which then converts the analog audio signal to obtain the digital audio signal S n .
• the microphone 40 can perform the analog-to-digital conversion of the analog audio signal S e (t) and directly supply the digital audio signal S n to the processing device 34.
• the processing device 34 is adapted to perform a processing on the digital audio signal S n to provide a digital audio file.
• the processing may comprise the conditioning of the digital audio signal S n , for example the application of a filter to the digital audio signal, the mixing of the digital audio signal with another digital audio signal and / or the recording of the digital audio file comprising the digital audio signal S n and possibly additional data.
• the transmission delay of the microphone 40 corresponds to the delay between the moment when the microphone begins to receive the sound signal S (t) and the moment when the processing device 34 starts the processing applied to the digital audio signal, for example the moment where the processing device 34 starts the conditioning of the digital audio signal S n , the moment when the processing device 34 starts mixing the digital audio signal S n with another digital audio signal or the moment when the processing device 34 starts to storing the digital audio file representative of the sound signal S (t).
• the calibration device 30 further comprises a support 44 disposed at least partially in the enclosure 32 and comprising holes 46 in which the microphones 40 are arranged in part.
• the support 40 is in contact with the loudspeaker 40. 36.
• the support 44 comprises an elastic material at least at each hole 46 so that the support 44 can slightly deform upon insertion of the microphone 40 into the hole 46.
• the support 44 is, for example, at least partly foam.
• each hole 46 has a shape complementary to a part of a microphone 40 so that, when a microphone 40 is disposed in a hole 46, the microphone 40 remains substantially immobile with respect to the speaker 32, for example by the friction exerted by the support 44 on the microphone 40.
• the holes 46 present in the support 44 may be identical. Alternatively, the holes 46 may have different shapes in the case where microphones of different shapes are used. In Figure 3, the holes 46 are shown in an aligned fashion.
• the enclosure 32 may be a single piece or comprise several pieces connected to each other.
• the enclosure 32 may comprise a frame whose internal wall has a shape complementary to the various elements housed in the enclosure 32.
• shims may, in addition, be arranged in the enclosure 32, between the enclosure 32 and the processing device 34, the battery 38, the loudspeaker 36 and / or the support 44 to facilitate the holding in position of these elements in the enclosure 32.
• the enclosure 32 is made of plastic material.
• Figure 4 is a view similar to Figure 3 of another embodiment of the support 44 in which the holes 46 are arranged at the corners of a regular polygon. Alternatively, the holes 46 may be divided into rows and columns.
• the support 44 may comprise a plurality of microphone clamps, preferably connected by a frame rigid to each other, each microphone 40 being held by one of the clamps when using the calibration device 30.
• the capsules of the microphones 40 are preferably placed relative to the speaker 36 so that the sound waves emitted by the loudspeaker are substantially flat when they reach the microphones. 40 and at the same time reach the capsules of the microphones 40.
• the capsules of the microphones 40 are disposed equidistant from the loudspeaker 36.
• the distance between the capsule of each microphone 40 and the speaker 36 is between 2 cm and 20 cm, preferably between 2 cm and 10 cm.
• FIG. 5 represents an embodiment of a method of calibrating the sound recording system 31.
• Step 50 corresponds to the mounting of the calibration device 30 which comprises the stack, in the chamber 32, of the processing device 34, the battery 38, the loudspeaker 36, and the support 44.
• the enclosure 32 holds the processor device 34, the battery 38, the speaker 36 and the support 44 in position.
• the speaker 32 ensures that the microphones 40 remain motionless relative to the loudspeaker 36 during the calibration operation.
• the process continues in step 52.
• step 52 sound signals are emitted by the loudspeaker 36. These sound signals are picked up by the microphones 40.
• Each sound signal may correspond to a pure sound emitted during a determined transmission duration, that is, ie to a sound signal at a single frequency.
• the frequency of the pure sound can be constant during the duration of emission or vary during the duration of emission.
• the frequency of the pure sound can increase or decrease with a constant rate of change during the transmission duration, which corresponds to a frequency ramp.
• step 54 The process continues in step 54.
• step 54 for each microphone 40, a digital audio signal S n is acquired by the processing device 34 from the sound signal picked up by the microphone in step 52, the digital audio signal S n being received or determined by the processing device 34.
• the processing device can perform various processing on digital audio signals Sn, including providing and storing audio files.
• Steps 52 and 54 are repeated for each sound signal provided by loudspeaker 36. The process proceeds to step 56.
• FIG. 6 schematically shows an exemplary envelope S3 ⁇ 4 of the control signal of loudspeaker 36 for the transmission of a sound signal and the digital audio signals S n] _ and S n 2 acquired by the processing device. 34 from the sound signals that are picked up by two microphones 40 during the transmission of the sound signal by the speaker 36.
• the envelope Su comprises, for example, successively a rising edge Attack, a steady level zone Sustain, and a falling edge.
• other forms of envelope S3 ⁇ 4 can be used.
• the instant t ] _ corresponds to the instant of detection of the rising edge of the signal S n] _ and the instant t2 corresponds to the instant of detection of the rising edge of the signal S n 2 ⁇
• characteristics of the microphones 40 are determined by the processor 34 from the analysis of the digital audio signals S n provided in step 54.
• the characteristics can be the transmission delay, the phase shift and / or the amplification ratio of each microphone 40.
• the shape of the support 44 is known in advance, the relative positions between the microphones 40 placed in the holes 46 and the speaker 36 are known in advance.
• the propagation delay of each sound signal from the loudspeaker 36 to each microphone 40 is therefore known beforehand.
• the configuration of the microphones 40 is defined so that the propagation delays of each sound signal emitted by the loudspeaker 36 to the microphones 40 are substantially identical.
• An exemplary method for analyzing digital audio signals is described in patent application FR 2764088.
• the analysis method may include comparing the digital audio signals with each other.
• the analysis method may comprise the determination of the delay At between the instant t] the beginning of the first digital audio signal S n ] _ with respect to the start time -2 of the second digital audio signal S n 2 as acquired by the processing device 34.
• the instant The beginning of a digital audio signal may correspond to the instant at which the digital audio signal exceeds a threshold.
• the digital audio signal is compared to a template by temporally moving the template relative to the digital audio signal until a criterion is met, for example the maximum overlap of the digital audio signal by the template.
• the start time of the digital audio signal is then obtained from the determined position of the template.
• the processing device 34 can modify some of its operating parameters according to the results obtained in step 56.
• the processing device 34 is adapted to modify, for each microphone 40 , the delay between the actual start of the digital audio signal acquired by the processing device 34 and corresponding to an audio signal picked up by the microphone 40 and the beginning of the processing applied by the processing device 34 to the digital audio signal. This delay is called the wait time afterwards.
• the treatment device can shift the start time of the digital audio signal by a time equal to the waiting time.
• the processing device 34 automatically modifies the delay times associated with the microphones so that processing of the digital audio signals by the processing device starts simultaneously, as if the start times of the digital audio signals were identical.
• the processing device 34 determines for which microphone 40 the delay At is the highest and, in step 58, the waiting times associated with the other microphones are then modified to that the start time of each digital audio signal corresponds to the start time of the digital audio signal having the highest delay.
• the processing performed by the processing device 34 may include the introduction of an additional delay for certain digital audio signals, in particular by delaying the start of the recording of digital audio files, for example to achieve a desired sound effect (creating an echo, obtaining an impression of distance, etc.).
• step 60 the processing device 34 determines whether the digital audio signals satisfy certain criteria. If the digital audio signals do not meet the criteria, the method returns to step 52 and a new calibration operation is performed. For example, digital audio signals can be compared to templates. If the digital audio signals satisfy the criteria, the process proceeds to step 62.
• step 62 the processing device 34 determines the phase shift between the digital audio signals acquired by the processing device 34 from the sound signals picked up by the microphones 40.
• the step 62 may not be present.
• step 64 the processor 34 may indicate to an operator that the calibration operation is complete. For example, it can be provided the display of information on a display screen indicating the delay associated with each microphone 40.
• Fig. 7 shows a more detailed embodiment of a method for determining the phases of the audio signals at step 62 previously described.
• step 70 sound signals are emitted by the loudspeaker 36. These sound signals are picked up by the microphones 40. Each sound signal corresponds to a pure sound emitted during a determined transmission duration, that is to say Saying a sound signal at a single frequency.
• the frequency of the pure sound can be constant during the duration of emission or vary during the duration of emission. By way of example, the frequency of the pure sound can increase or decrease with a constant rate of change during the transmission duration, which corresponds to a frequency ramp.
• step 72 for each sound signal and for each pair of microphones comprising a first microphone and a second microphone, the processing device 34 can determine the sum of the first digital audio signal associated with the first microphone and the second associated digital audio signal. at the second microphone to determine the phase shift between the first and second digital audio signals.
• the processing device 34 can modify the digital audio signals S n to compensate for the phase offsets determined in step 72.
• the processing device 34 determines the digital audio signal having a correct phase and digital audio signals that do not have the correct phase are changed.
• the correct phase corresponds to the phase common to the largest number of digital audio signals among all the signals acquired by the processing device 34. Steps 52 to 64 of the microphone calibration 40 of the pick-up system 31 may advantageously be performed quickly and automatically by the recording device 31.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Circuit For Audible Band Transducer (AREA)

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• 2016
  • 2016-08-01 FR FR1657451A patent/FR3054769B1/fr active Active
• 2017
  • 2017-07-31 WO PCT/FR2017/052148 patent/WO2018024974A1/fr unknown
  • 2017-07-31 US US16/322,797 patent/US20190182591A1/en not_active Abandoned
  • 2017-07-31 EP EP17757804.4A patent/EP3491842A1/de not_active Withdrawn

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