WO2011048101A1 - Traitement de chocs acoustiques - Google Patents

Traitement de chocs acoustiques Download PDF

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Publication number
WO2011048101A1
WO2011048101A1 PCT/EP2010/065729 EP2010065729W WO2011048101A1 WO 2011048101 A1 WO2011048101 A1 WO 2011048101A1 EP 2010065729 W EP2010065729 W EP 2010065729W WO 2011048101 A1 WO2011048101 A1 WO 2011048101A1
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WO
WIPO (PCT)
Prior art keywords
audio signal
acoustic
threshold
signal
frequency band
Prior art date
Application number
PCT/EP2010/065729
Other languages
English (en)
Inventor
Nicolas Louboutin
Original Assignee
St-Ericsson (France) Sas
St-Ericsson Sa
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 St-Ericsson (France) Sas, St-Ericsson Sa filed Critical St-Ericsson (France) Sas
Publication of WO2011048101A1 publication Critical patent/WO2011048101A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/60—Substation equipment, e.g. for use by subscribers including speech amplifiers
    • H04M1/6016—Substation equipment, e.g. for use by subscribers including speech amplifiers in the receiver circuit
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F11/00—Methods or devices for treatment of the ears or hearing sense; Non-electric hearing aids; Methods or devices for enabling ear patients to achieve auditory perception through physiological senses other than hearing sense; Protective devices for the ears, carried on the body or in the hand
    • A61F11/06—Protective devices for the ears
    • A61F11/14—Protective devices for the ears external, e.g. earcaps or earmuffs
    • A61F11/145—Protective devices for the ears external, e.g. earcaps or earmuffs electric, e.g. for active noise reduction
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
    • H04R2430/01—Aspects of volume control, not necessarily automatic, in sound systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
    • H04R2430/03—Synergistic effects of band splitting and sub-band processing

Definitions

  • the present invention relates to signal processing. More particularly, it aims to improve the detection and processing of anomalies in audio signals, in order to protect the organs of hearing of a user to whom the audio signal is sent.
  • Audio systems are subject to a certain number of regulations concerning the protection of users' organs of hearing.
  • acoustic trauma is an irreversible injury to the organs of hearing due to exposure to sound of too high an intensity.
  • the common devices therefore already have sound limiters.
  • limiters monitor the audio signal emitted over time, and detect peaks of sound intensity in order to cut off the audio signal when an intensity threshold is reached.
  • directive 2003/ 0/EC sets the threshold at 137 dB(C) (where dB(C) represents a weighted decibel using a filter representing the frequency response of the human ear for signals of high intensity), the 29CFR1910.95 regulations set the threshold at 140 dB(C), and the ITU-T P.360 recommendations set the threshold at 125 dB(A) and 118 dB(A) for a headset (dB(A) represents a weighted decibel using a filter representing the frequency response of the human ear for signals of average intensity).
  • An acoustic shock can be defined as exposure to a rapid transition of a sound of a given intensity to a sound of a higher intensity. In other words, it is the consequence of a sudden elevation of the sound level, more than the exceeding of an absolute threshold.
  • An acoustic shock can for example be caused by an audio signal coding error. It can also simply result from the dynamics of the changes in intensity and/or frequency in the reproduced sound.
  • An acoustic shock can occur in ranges of intensity that are lower than the thresholds recommended by the directives and regulations listed above.
  • an acoustic shock can be very unpleasant for the user. In the worst cases, repeated acoustic shocks can irreversibly damage the inner ear.
  • a method for processing acoustic shocks in an audio signal comprising the steps of:
  • the invention therefore proposes processing the signal by frequency bands in order to detect an acoustic shock. This allows detecting acoustic shocks in a more refined manner, and to adapt how this shock is processed also in a more refined manner.
  • the ear does not have the same sensitivity across the entire audible frequency spectrum.
  • abrupt changes in the sound reproduced for the user can consist of a transfer of energy from one frequency band to another, without increasing the average energy level.
  • the invention allows adapting the detection to each frequency band selected.
  • the signal can be divided into three frequency bands: one for the lows, one for the mediums, and one for the highs.
  • the invention is not limited by the number of bands. For example, it is possible to choose even smaller frequency bands when there are significant computational resources.
  • the method can be implemented in a sound reproduction device such as a portable audio or video player, a mobile telephone, or other device.
  • the method allows handling acoustic shocks which can result from coding errors of a recording medium during reads or writes, or coding errors in the transmission of an audio signal for example.
  • the energy of the audio signal can allow measuring the sound intensity of the corresponding acoustic signal.
  • the threshold is an average energy of the audio signal.
  • the threshold is thus adapted to each audio signal processed.
  • An acoustic shock can have a very different effect depending on the signal being processed, because the effect of the shock can depend on the state of contraction of the muscles in the ear at the moment the shock occurs.
  • the detection can be based on several comparisons in several frequency bands. Thus one can choose the level of detail in the analysis for detecting the acoustic shock. As mentioned above, the ear does not have the same sensitivity across the entire range of audible frequencies. In addition, depending on the audio signal being processed, acoustic shocks can appear in particular frequency bands.
  • the shock is harmless to the user's ear. It is then possible to refrain from determining whether an acoustic shock is present.
  • the second threshold is representative of one of the following:
  • a noise floor can be noise generated by sources of interference.
  • it can be noise introduced by components of the acoustic signal reproduction device.
  • the crackling of a speaker is part of the noise floor.
  • Environmental noise can be noise issuing from the environment in which the acoustic signal reproduction device is located. For example, if a mobile telephone is in a concert hall, the sound of the music is environmental noise. Such noise can be captured by a microphone. A fixed sound level for the reproduction of the audio signal can correspond to the volume level as adjusted by the user.
  • the second threshold can also be representative of a combination of these levels.
  • the detection of acoustic shock can be fine-tuned.
  • the effect of an acoustic shock can depend on the state of the user's ear.
  • the noises mentioned above and the volume of the reproduced audio signal can render the determination of acoustic shock more or less relevant.
  • a step can be provided consisting of applying, for the comparisons made, an acoustic compensation to each frequency band in order to compensate for the filter effect of an acoustic system intended to reproduce the audio signal.
  • the acoustic dynamics of the system can have non-negligible filter effects on the perception of the audio signal and on the effect of an acoustic shock. It can therefore be relevant to take it into account in acoustic shock detection.
  • Such compensation can for example take into account the mechanics of the system, the type of speaker, the digital filters used, audio gain, and more generally the acoustic response of the system, or some other aspect.
  • steps can be provided consisting of attenuating the audio signal in a frequency band when an acoustic shock has been detected in the audio signal.
  • the audio signal is attenuated only in a frequency band in which an acoustic shock has been detected.
  • the response to the detection of an acoustic shock can be fine- tuned.
  • the level of detail of the detection can depend on the complexity of the processing (number of frequency bands, size and rate of advancement of the measurement window).
  • the computer program, the integrated circuit, the system, as well as the terminal present at least the same advantages as those provided by the method according to the first aspect of the invention.
  • FIG. 1 illustrates a general context for implementing an embodiment of the invention
  • FIG. 2 is a flowchart of the steps of a process according to an embodiment of the invention.
  • FIG. 3 illustrates different objects implemented in the steps of the flowchart in Figure 2;
  • FIG. 4 illustrates the compensation of the energy evolution spectrum according to one embodiment;
  • FIG. 6 illustrates a system according to one embodiment of the invention.
  • an audio signal is sent from a source SRC to a user USR.
  • the audio signal passes through a communication channel TRANS to an audio reproduction device RECEIV. Once the audio signal is received by the device RECEIV, it is emitted for reproduction for the user.
  • the device RECEIV is a mobile communication terminal
  • the communication channel TRANS represents a telecommunications network
  • the source SRC represents another communication terminal which communicates with the device RECEIV.
  • the source SRC is a means of storing data such as a digital compact disk, a memory card, a hard drive, a USB key, or other device;
  • the device RECEIV is an audio or video player, and the communication channel TRANS represents the decoding and player circuits of the device RECEIV.
  • Figure 2 is a flowchart representing steps implemented in this embodiment.
  • Figure 3 represents certain objects used in this embodiment.
  • an audio signal SIG to be sent to a user is received. Detection of a possible acoustic shock in this signal is proposed.
  • a first spectrum SP1 is obtained, subdivided into three frequency bands B1 , B2, and B3. Also obtained for the interval T2 is a second spectrum SP2, subdivided in the same manner as SP1.
  • the band B1 corresponds to the frequencies of 20 to 500 Hz (low), the band B2 to the frequencies 500 Hz to 5 kHz (medium), and the band B3 from 5 kHz to 20 kHz (high).
  • the bands B1 , B2, and B3 are of identical respective sizes.
  • a person skilled in the art can choose this identical size as a function of the computational resources available for implementing the process. The more computational resources there are, the smaller and more numerous the frequency bands can be that he uses.
  • FFT Fast Fourier Transforms
  • step S23 a variation in the energy between the intervals T1 and T2 is determined, for each frequency band B1 , B2, and B3
  • the energy increase is compared to a threshold during the step S24.
  • the result of this comparison allows determining during the step S25 whether the audio signal includes an acoustic shock.
  • the audio signal includes an acoustic shock.
  • the duration of the intervals can be configurable as will be evident to a person skilled in the art. These intervals advance along the signal at a rate which can also be configured as a function of the computational performance.
  • An energy increase threshold can be 50 dBSPL. This threshold allows protecting the ear at rest for all sounds higher than 20 dbSPL because the ear muscle reflex appears at about 70 dBSPL ("Sound Pressure Level").
  • This muscle reflex appears at about 70dB SPL but not for very long (it is a reflex related to a sudden increase and is maintained for a short time only). It takes about 40ms to trigger.
  • a dynamic threshold can also be chosen, for example, the average energy of the audio signal measured over a given interval of time (shorter or longer depending on the computational resources available).
  • the choice of threshold can also take into account the noise attributed to the acoustic system components, or the noise attributed to the environment in which the reproduction of the audio signal occurs.
  • the volume selected by the user for listening to the audio signal can also be taken into account.
  • the user's ear is already in a condition that provides better resistance to acoustic shock because the muscles of the ear are already contracted in order to attenuate these noises.
  • this second comparison is made at the highest level of the acoustic shock.
  • a compensation of the audio signal as a function of the acoustic properties of the audio signal reproduction system is provided.
  • a filter representative of these properties is applied to the spectrum obtained during the step S21.
  • a filter is applied to the energy evolution spectrum ⁇ obtained during the step S23.
  • the compensation notably aims to take into account effects which do not arise from the signal itself, and from any acoustic shocks that it contains, but from effects of the signal reproduction system.
  • the effect of acoustic shocks will also be greatly reduced in the low frequencies, to the extent that it may be relevant to take this into account in the shock detection.
  • the acoustic properties of the system can for example comprise the dynamics of the speakers, the audio gain, the configuration and type of materials used to form the cases of the resonance chambers, etc.
  • FIG. 4 illustrates a compensation according to one embodiment.
  • the energy evolution spectrum for an audio signal ⁇ on different frequency bands B1 to B6 is represented, before (the left graph ⁇ ) and after (the right graph LEm) the application of a compensation filter COMPENS.
  • the filter COMPENS has a general bell shape that first rises then descends, with a peak in the B5 band.
  • the filter COMPENS represents a system which greatly attenuates the sounds in the band B1 -B3, and to a lesser extent in the band B6.
  • the application of the filter therefore allowed focusing on the bands B4 and B5 in order to make the comparison with the thresholds and detect an acoustic shock.
  • comparison thresholds are modified as a function of the properties of the acoustic system. This embodiment can economize the calculations to be done.
  • an acoustic shock When an acoustic shock has been detected, one can for example apply an attenuation filter to the audio signal, in the frequency band where the acoustic shock is located.
  • Figure 5 illustrates a spectrum of an audio signal, divided into three frequency bands B1 , B2, and B3 before (the left graph SP) and after (the right graph SPATT) the application of an attenuation filter ATT.
  • the filter ATT is then applied which is substantially flat in shape in the bands B1 and B3 and has a bell shape that rises and then falls in the band B3.
  • the filter ATT therefore barely attenuates the signal in the bands B1 and B2 and attenuates the signal in the band B3.
  • the attenuation of the signal can be correlated (for example proportionally) to the energy increase detected in the band B3.
  • the filter is applied only to the band where the shock was detected.
  • a computer program of the invention can be realized according to a general algorithm deduced from the general flowchart in Figure 2 and from the present description.
  • An integrated circuit of the invention can be realized by techniques known to a person skilled in the art and be configured to implement a process according to the invention.
  • a system of the invention can be realized in an integrated circuit in the form of a System on Chip (SoC).
  • SoC System on Chip
  • the system comprises a processing unit PROC configured to implement a process of the invention.
  • the unit PROC comprises an integrated circuit of the invention, and as a further example the unit PROC comprises a processor for implementing a computer program according to the invention.
  • the unit PROC comprises an acoustic shock detection unit DTCT for detecting an acoustic shock in an audio signal.
  • the unit PROC also comprises an attenuation unit ATT for attenuating the audio signal when an acoustic shock has been detected.
  • the system also comprises a unit for reproducing the audio signal SPK.
  • the unit for reproducing the audio signal SPK is a speaker or an audio headset.
  • the system also comprises a memory MEM for storing various data, for example computational data for the processing unit, or a computer program according to the invention so that it can be implemented by a processor of the unit PROC.
  • a memory MEM for storing various data, for example computational data for the processing unit, or a computer program according to the invention so that it can be implemented by a processor of the unit PROC.
  • the audio signal processed by the processing unit PROC is stored in the memory MEM.
  • the audio signal is received by a communication unit COM.
  • the system can for example be a mobile communications terminal.

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  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Biomedical Technology (AREA)
  • Psychology (AREA)
  • Otolaryngology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Biophysics (AREA)
  • Circuit For Audible Band Transducer (AREA)

Abstract

La présente invention concerne un procédé de traitement de chocs acoustiques dans un signal audio. Le procédé consiste à diviser le signal en bandes de fréquence ; à détecter une variation de l'énergie du signal audio dans chaque bande de fréquence ; à effectuer une première comparaison dans le but de comparer la variation d'énergie pour au moins une bande de fréquence avec un premier seuil ; et à déterminer un choc acoustique, sur la base du résultat de la première comparaison, lorsque la variation est une augmentation supérieure au premier seuil.
PCT/EP2010/065729 2009-10-20 2010-10-19 Traitement de chocs acoustiques WO2011048101A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0957368 2009-10-20
FR0957368 2009-10-20

Publications (1)

Publication Number Publication Date
WO2011048101A1 true WO2011048101A1 (fr) 2011-04-28

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PCT/EP2010/065729 WO2011048101A1 (fr) 2009-10-20 2010-10-19 Traitement de chocs acoustiques

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113132880A (zh) * 2021-04-16 2021-07-16 深圳木芯科技有限公司 基于双麦克风架构的冲击噪声抑制方法和系统

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050018862A1 (en) * 2001-06-29 2005-01-27 Fisher Michael John Amiel Digital signal processing system and method for a telephony interface apparatus
US20050058274A1 (en) * 2003-09-11 2005-03-17 Clarity Technologies, Inc. Acoustic shock prevention
WO2007014795A2 (fr) * 2006-06-13 2007-02-08 Phonak Ag Procede et systeme de detection de chocs acoustiques et application dudit procede a des protheses auditives
GB2456296A (en) * 2007-12-07 2009-07-15 Hamid Sepehr Audio enhancement and hearing protection by producing a noise reduced signal

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050018862A1 (en) * 2001-06-29 2005-01-27 Fisher Michael John Amiel Digital signal processing system and method for a telephony interface apparatus
US20050058274A1 (en) * 2003-09-11 2005-03-17 Clarity Technologies, Inc. Acoustic shock prevention
WO2007014795A2 (fr) * 2006-06-13 2007-02-08 Phonak Ag Procede et systeme de detection de chocs acoustiques et application dudit procede a des protheses auditives
GB2456296A (en) * 2007-12-07 2009-07-15 Hamid Sepehr Audio enhancement and hearing protection by producing a noise reduced signal

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CHOY G ET AL: "Subband-Based Acoustic Shock Limiting Algorithm On A Low Resource DSP System", 20030901, 1 September 2003 (2003-09-01), pages 2869, XP007007046 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113132880A (zh) * 2021-04-16 2021-07-16 深圳木芯科技有限公司 基于双麦克风架构的冲击噪声抑制方法和系统
CN113132880B (zh) * 2021-04-16 2022-10-04 深圳木芯科技有限公司 基于双麦克风架构的冲击噪声抑制方法和系统

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