EP1792305A1 - Procédé et dispositif d'évaluation de l'efficacité d'une fonction de réduction de bruit destinée à être appliquée à des signaux audio - Google Patents
Procédé et dispositif d'évaluation de l'efficacité d'une fonction de réduction de bruit destinée à être appliquée à des signaux audioInfo
- Publication number
- EP1792305A1 EP1792305A1 EP05802558A EP05802558A EP1792305A1 EP 1792305 A1 EP1792305 A1 EP 1792305A1 EP 05802558 A EP05802558 A EP 05802558A EP 05802558 A EP05802558 A EP 05802558A EP 1792305 A1 EP1792305 A1 EP 1792305A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- signal
- noise
- frame
- loudness
- noise reduction
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000005236 sound signal Effects 0.000 title claims abstract description 29
- 238000012360 testing method Methods 0.000 claims abstract description 36
- 230000009467 reduction Effects 0.000 claims description 51
- 230000003595 spectral effect Effects 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 13
- 238000004364 calculation method Methods 0.000 claims description 12
- 238000004590 computer program Methods 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 3
- 230000007480 spreading Effects 0.000 claims description 3
- 230000006870 function Effects 0.000 description 44
- 238000011156 evaluation Methods 0.000 description 12
- 230000008447 perception Effects 0.000 description 9
- 230000005540 biological transmission Effects 0.000 description 5
- 238000004422 calculation algorithm Methods 0.000 description 3
- 230000003313 weakening effect Effects 0.000 description 3
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Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/48—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use
- G10L25/69—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use for evaluating synthetic or decoded voice signals
Definitions
- the present invention relates generally to reduction functions "of" bT ⁇ if ⁇ "applicatio” Abre ⁇ â ⁇ ⁇ My IGMG "x ⁇ a" ûcliâ
- the invention relates to a method and apparatus for evaluating the efficiency of a noise reduction function for application to audio signals.
- the known methods for evaluating the effectiveness of a noise reduction function are based on objective measurements to characterize the RB function considered.
- noise reduction (NR) function such as the SNRI method
- SNRI method although indicative of the effectiveness of a given noise reduction function
- known methods for evaluating the effectiveness of a noise reduction (NR) function are not known. not sufficiently powerful because they do not take into account the human perception of the signal processed by the RB function, to characterize its effectiveness.
- the attenuation of the useful signal (voice signal for example) by the noise reduction function may be detrimental to the sound perception of the resulting audio signal by the end user of the equipment restoring the audio signal.
- the present invention therefore aims to provide a method of evaluating a noise reduction function, the effectiveness of which is superior to known methods, due to the fact that human perception characteristics are taken into account in the process of noise reduction. evaluation of a noise reduction function.
- the invention relates, according to a first aspect, to a method of evaluating the efficiency of a noise reduction function intended to be applied to audio signals, this method comprising a preliminary step of obtaining a predefined test audio signal X [m] containing a noise-free useful signal, a noisy signal, Xb [m], obtained by adding a predefined noise signal at the test signal X [m], and a processed signal Y [m] obtained by applying the noise reduction function at the noisy signal Xb [m].
- the method is remarkable in that it includes a loudness measurement step of all or part of the frames m of the signals X [m], Xb " p] ⁇ ⁇ [mJ above.
- Such a method of evaluating a noise reduction function is significantly more efficient than conventional evaluation methods, since it takes into account a characteristic relating to human auditory perception (loudness), calculated in particular on the frames. test signals and processed.
- An evaluation method according to the invention thus takes into account the subjective perception, by a human being, of a reduction of the useful signal level produced by the noise reduction function, contrary to the known methods.
- calculating the average loudness density Su (m) of any frame m of a given audio signal u comprises the following steps :
- the invention relates to a test equipment for evaluating the efficiency of a noise reduction function.
- this equipment comprises means adapted to implement a method as explained above.
- the present invention also relates to a computer program on an information carrier, this program comprising instructions adapted to the implementation of a method according to the invention, when the program is loaded and executed in a computer system.
- FIG. 1 represents a test environment for evaluating a noise reduction function in accordance with the present invention
- FIG. 2 is a flowchart illustrating a method of evaluating the efficiency of a noise reduction function, in accordance with the invention.
- FIG. 3 is a flowchart illustrating the calculation of the average loudness density of a frame of an audio signal, according to an embodiment of rMlisàiiôn pTéf ⁇ re "d ⁇ Ti ⁇ ven ⁇ ⁇ r ⁇
- Figure 1 shows a test environment in which the present invention can be implemented to evaluate a noise reduction function.
- such a test environment comprises a source of audio signals delivering audio signals X (n) containing only useful signals (devoid of noise), for example speech signals; and a noise source 1 1 delivering predefined noise signals.
- a predefined noise contribution is added to the selected test signal X (n), as represented by the addition operator 15.
- the audio signal resulting from this addition of noise to the test signal X (n) is denoted Xb (n) and is designated by the expression "noisy signal”.
- the noisy signal Xb (n) then constitutes the input signal of a noise reduction module 12 (RB) implementing the noise reduction function whose efficiency must be evaluated, according to the invention.
- the noise reduction module 12 outputs an audio signal, denoted Y (n), processed according to the noise reduction algorithm used.
- the signal Y (n) is referred to as the "processed signal”.
- the processed signal Y (n) is then delivered to a test equipment 13 implementing an evaluation method according to the invention.
- the test equipment 13 receives as input the test signal X (n) and the noisy signal Xb (n).
- the test equipment 13 according to the invention outputs an evaluation result 14 of the noise reduction function.
- this evaluation result consists of the value of an efficiency index (IE) whose method of calculation will be described below.
- the aforementioned audio signals X (n), Xb (n) and Y (n) are signals sampled in a digital format (n denoting any sample).
- test equipment 13 comprises hardware means (e) "and / or" lô ⁇ icial "" to APLES ⁇ ⁇ to ⁇ " ⁇ rn ⁇ ftré ert” work ûn ⁇ ⁇ ⁇ ⁇ r ⁇ c ⁇ è evaluation according to the invention.
- the steps of the evaluation method according to the invention are determined by the instructions of a computer program used in such test equipment.
- the method according to the invention is then implemented when the aforementioned program is loaded into computer means incorporated in the test equipment, and whose operation is then controlled by the execution of the program.
- computer program herein refers to one or more computer programs forming a set (software) whose purpose is the implementation of the invention when it is executed by an appropriate computer system. Accordingly, the invention also relates to such a computer program, particularly in the form of software stored on an information carrier.
- an information carrier may be constituted by any entity or device capable of storing a program according to the invention.
- the medium in question may comprise a hardware storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a hard disk.
- the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.
- the information medium can also be a transmissible immaterial medium, such as an electrical or optical signal that can be conveyed via an electrical or optical cable, by radio or by other means.
- a program according to the invention can in particular be downloaded to an Internet type network.
- a computer program according to the invention can use any programming language and be in the form of source code, object code, or intermediate code between source code and object code (for example eg, a partially compiled form), or in any other form desirable for implementing a method according to the invention.
- the signals X (n), Xb (n) and Y (n) obtained beforehand and respectively corresponding to the test audio signal, to the noisy test signal and to the signal processed by the noise reduction function. noise are received as input to the aforementioned test equipment 13 (FIG 1).
- the test signal X (n) is a speech signal devoid of noise.
- the noisy signal Xb (n) then represents the initial speech signal X (n) degraded by a noisy environment (background or ambient noise), and the signal Y (n) the signal Xb (n) after noise reduction.
- the signal X (n) is generated in an anechoic chamber.
- the signal X (n) can also be generated in a "quiet” room having a reverberation time "average” (less than 0.5 seconds).
- each frame, denoted m, of signal contains a number predetermined, signal E1 step is therefore a change in rate of each of these signals.
- the signals X [m], Xb [m], Y [m] resulting from the passage in frame rate are the subject of a voice activity detection (DAV) in order to determine if each respective current frame of index m of these signals, is a frame containing only noise, "noise frame", or a frame containing speech, "useful signal frame”.
- DAV voice activity detection
- FIG. 2 at the output of step E2, four types of frames are selected from the signals X [m], Xb [m] and Y [m]:
- the next step E3 is a loudness measurement step of all or part of the frames of the signals X [m], Xb [m] and Y [m].
- the mean loudness densities S ⁇ (m_utile) and S ⁇ (useful m) of each of the useful signal frames "m_utile” of the test signal X [m] and of the processed signal Y [m are calculated respectively.
- step E4 which follows, the averages are calculated, Sxb bmit, S ⁇ _bmit,
- Sx _ useful, Sy useful, above mean loudness densities on all relevant frames (noise frames or speech frames) of each of the corresponding signals (X [m], Y [m] or Xb [m]).
- a first pair D2 of average mean loudness density values corresponding to the noise frames of the noisy (Xb) and processed (Y) signals Sxb bmit and SY_ noise; and, secondly, a second pair D3 of average loudness mean mean values corresponding to the active speech frames of the test (X) and processed (Y) signals:
- step E5 the pair D3 of average loudness mean mean values, is used to calculate a coefficient ⁇ obtained by the formula below:
- the coefficient ⁇ is indicative of the attenuation, as perceived by the human ear, of the useful signal (active speech signal) due to the application of the noisy signal noise reduction function (Xb).
- step E6 the two average D2 values of the mean loudness densities corresponding to the noise frames of the noisy (Xb) and processed (Y) signals: S ⁇ b_ noise and S ⁇ _bmit are used together with the coefficient ⁇ calculated in step E5, to calculate the efficiency index IE according to the formula below:
- S ⁇ _noise coefficient ⁇ which is indicative of the subjective perception by the human ear of the weakening of the useful signal in the signal (Y) resulting from the processing by the noise reduction function.
- the (decimal) value of this index is then converted into decibels (dB) and then saved (D4) to be used to characterize the efficiency of the noise reduction function.
- the value obtained (D4) of the index IE is compared with at least one predetermined value of this index, in order to determine a level of efficiency of the noise reduction function.
- the level of efficiency of the noise reduction function (RB) is determined according to the following table:
- the efficiency index IE has been calculated from a database of audio signals which has moreover been subject to subjective tests according to Recommendation P.835 of I 1 ITU-T (International Telecommunications Union - Telecommunications sector standardization). The change in the value of the IE index, obtained in function of the audio signals from the database, was found to be in line with subjective test results.
- the calculation according to the invention of the average loudness density Su (m) of any frame m of a given audio signal u [m], comprises the steps set out below. .
- a windowing is applied to the frame m of the signal u [m], for example a windowing of the Hanning, Hamming or equivalent type. We then obtain a windowed frame u-w [m].
- a fast Fourier transform (FFT) is applied to the windowed frame u-w [m] and a corresponding frame U (m, f) in the frequency domain is accordingly obtained.
- FFT fast Fourier transform
- step E33 the power spectral density ⁇ u (m, f) of the frame U (m, f) is calculated. Such a calculation is known to those skilled in the art and will not, therefore, be detailed here.
- step E35 a convolution with the spreading function is applied to the power spectral density on the Barks scale, Bu (m, b), and a spectral density spread on the screen is consequently obtained.
- scale of Barks noted Eu (m, b).
- step E36 a calibration of the spectral density spread on the Barks scale, Eu (m, b), is performed by the respective factors of power scaling and loudness scaling.
- step E37 The step obtained in the previous step is then converted (step E37) to the scale of the phones.
- the conversion on the scale of the phones is carried out based on the isosonic curves (Fletcher curves) in accordance with the standard NF ISO 226 "Normal isosonic lines".
- step E38 is carried out a conversion on the scale of sones of the size previously converted into phones.
- the conversion to sones is made in accordance with Zwicker's law that:
- a number B of loudness density values, S ⁇ (m, b), of the frame m for the critical band b are available, B being the number of critical bands considered. in the Barks scale and the index b varying from 1 to B.
- the sampling frequency Fe of the signal u (n) considered is equal to 8 kHz (kilo Hertz), 18 critical bands are considered in the Barks scale.
- step E39 the mean loudness density Su (m) of the frame m is calculated from said B loudness density values, according to the following equation:
- the average loudness density Su (m) according to the invention of a frame m is therefore the average of the B loudness density values, Su (m, b), of the frame m for a critical band b considered.
- each average loudness value is saved for use in accordance with the evaluation method of a noise reduction function, according to the invention (see Figure 2, D1).
- the audio signals used are speech signals
- the present invention makes it possible to evaluate the effectiveness of any noise reduction function applying to audio signals in the generic sense of the term .
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- Engineering & Computer Science (AREA)
- Computational Linguistics (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- Audiology, Speech & Language Pathology (AREA)
- Human Computer Interaction (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0452087A FR2875633A1 (fr) | 2004-09-17 | 2004-09-17 | Procede et dispositif d'evaluation de l'efficacite d'une fonction de reduction de bruit destinee a etre appliquee a des signaux audio |
PCT/FR2005/002262 WO2006032751A1 (fr) | 2004-09-17 | 2005-09-12 | Procede et dispositif d'evaluation de l'efficacite d'une fonction de reduction de bruit destinee a etre appliquee a des signaux audio |
Publications (1)
Publication Number | Publication Date |
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EP1792305A1 true EP1792305A1 (fr) | 2007-06-06 |
Family
ID=34948876
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP05802558A Withdrawn EP1792305A1 (fr) | 2004-09-17 | 2005-09-12 | Procédé et dispositif d'évaluation de l'efficacité d'une fonction de réduction de bruit destinée à être appliquée à des signaux audio |
Country Status (4)
Country | Link |
---|---|
US (1) | US20080255834A1 (fr) |
EP (1) | EP1792305A1 (fr) |
FR (1) | FR2875633A1 (fr) |
WO (1) | WO2006032751A1 (fr) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2894707A1 (fr) * | 2005-12-09 | 2007-06-15 | France Telecom | Procede de mesure de la qualite percue d'un signal audio degrade par la presence de bruit |
CN112562740A (zh) * | 2020-11-25 | 2021-03-26 | 厦门亿联网络技术股份有限公司 | 一种噪声消除测试方法、系统、音视频设备和存储介质 |
CN112530460A (zh) * | 2020-11-30 | 2021-03-19 | 厦门亿联网络技术股份有限公司 | 语音增强质量评估方法、装置、终端及存储介质 |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5574824A (en) * | 1994-04-11 | 1996-11-12 | The United States Of America As Represented By The Secretary Of The Air Force | Analysis/synthesis-based microphone array speech enhancer with variable signal distortion |
FI100840B (fi) * | 1995-12-12 | 1998-02-27 | Nokia Mobile Phones Ltd | Kohinanvaimennin ja menetelmä taustakohinan vaimentamiseksi kohinaises ta puheesta sekä matkaviestin |
US6446038B1 (en) * | 1996-04-01 | 2002-09-03 | Qwest Communications International, Inc. | Method and system for objectively evaluating speech |
FI114833B (fi) * | 1999-01-08 | 2004-12-31 | Nokia Corp | Menetelmä, puhekooderi ja matkaviestin puheenkoodauskehysten muodostamiseksi |
US6490552B1 (en) * | 1999-10-06 | 2002-12-03 | National Semiconductor Corporation | Methods and apparatus for silence quality measurement |
FI116643B (fi) * | 1999-11-15 | 2006-01-13 | Nokia Corp | Kohinan vaimennus |
DE60104091T2 (de) * | 2001-04-27 | 2005-08-25 | CSEM Centre Suisse d`Electronique et de Microtechnique S.A. - Recherche et Développement | Verfahren und Vorrichtung zur Sprachverbesserung in verrauschte Umgebung |
US7590530B2 (en) * | 2005-09-03 | 2009-09-15 | Gn Resound A/S | Method and apparatus for improved estimation of non-stationary noise for speech enhancement |
-
2004
- 2004-09-17 FR FR0452087A patent/FR2875633A1/fr active Pending
-
2005
- 2005-09-12 US US11/663,233 patent/US20080255834A1/en not_active Abandoned
- 2005-09-12 EP EP05802558A patent/EP1792305A1/fr not_active Withdrawn
- 2005-09-12 WO PCT/FR2005/002262 patent/WO2006032751A1/fr active Application Filing
Non-Patent Citations (1)
Title |
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See references of WO2006032751A1 * |
Also Published As
Publication number | Publication date |
---|---|
FR2875633A1 (fr) | 2006-03-24 |
US20080255834A1 (en) | 2008-10-16 |
WO2006032751A1 (fr) | 2006-03-30 |
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