EP1016071A1 - Procede de detection d'activite vocale - Google Patents
Procede de detection d'activite vocaleInfo
- Publication number
- EP1016071A1 EP1016071A1 EP98943998A EP98943998A EP1016071A1 EP 1016071 A1 EP1016071 A1 EP 1016071A1 EP 98943998 A EP98943998 A EP 98943998A EP 98943998 A EP98943998 A EP 98943998A EP 1016071 A1 EP1016071 A1 EP 1016071A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- frame
- signal
- noise
- band
- degree
- 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.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 34
- 230000000694 effects Effects 0.000 title claims abstract description 26
- 238000012545 processing Methods 0.000 claims abstract description 7
- 230000007774 longterm Effects 0.000 claims description 19
- 230000001755 vocal effect Effects 0.000 claims description 17
- 238000001228 spectrum Methods 0.000 claims description 8
- 230000001419 dependent effect Effects 0.000 claims description 2
- 230000001629 suppression Effects 0.000 abstract 3
- 230000003595 spectral effect Effects 0.000 description 21
- 230000006870 function Effects 0.000 description 17
- 230000000873 masking effect Effects 0.000 description 14
- 238000001514 detection method Methods 0.000 description 11
- 230000004044 response Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 5
- 238000012935 Averaging Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000007480 spreading Effects 0.000 description 3
- 210000000721 basilar membrane Anatomy 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000002964 excitative effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; 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
- G10L25/78—Detection of presence or absence of voice signals
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; 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
- G10L25/93—Discriminating between voiced and unvoiced parts of speech signals
- G10L2025/932—Decision in previous or following frames
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; 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
- G10L25/93—Discriminating between voiced and unvoiced parts of speech signals
- G10L2025/935—Mixed voiced class; Transitions
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; 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
- G10L25/93—Discriminating between voiced and unvoiced parts of speech signals
- G10L2025/937—Signal energy in various frequency bands
Definitions
- the present invention relates to digital techniques for processing speech signals. It relates more particularly to techniques using voice activity detection in order to carry out differentiated processing depending on whether the signal supports voice activity or not.
- the digital techniques in question come from various fields: speech coding for transmission or storage, speech recognition, noise reduction, echo cancellation ...
- the main difficulty with methods of detecting voice activity is the distinction between voice activity and the accompanying noise.
- the use of a conventional denoising technique does not make it possible to deal with this difficulty, since these techniques themselves use noise estimates which depend on the degree of vocal activity of the signal.
- a main aim of the present invention is to improve the noise robustness of the methods for detecting voice activity.
- the invention thus proposes a method for detecting voice activity in a digital speech signal processed by successive frames, in which the speech signal is subjected to denoising taking into account estimates of the noise included in the signal, updated day for each frame in a manner dependent on at least one degree of voice activity determined for said frame.
- a priori denoising of the speech signal of each frame is carried out on the basis of noise estimates obtained during the processing of at least one previous frame, and the energy variations of the denoised signal are analyzed.
- a priori to detect the degree of voice activity of said frame is carried out on the basis of noise estimates obtained during the processing of at least one previous frame, and the energy variations of the denoised signal are analyzed.
- a priori to detect the degree of voice activity of said frame.
- the fact of carrying out the detection of voice activity (according to a method which can generally be any known method) on the basis of an a priori denoised signal Significantly improves the performance of this detection when the surrounding noise is relatively high.
- the method for detecting voice activity according to the invention will be illustrated in a system for denoising a speech signal. It will be understood that this method can find applications in many other types of digital speech processing in which it is desired to have information on the degree of vocal activity of the processed signal: coding, recognition, echo cancellation, etc. .
- FIG. 1 is a block diagram of a denoising system putting in implements the present invention
- FIGS. 2 and 3 are flowcharts of procedures used by a voice activity detector of the system of Figure 1;
- FIG. 4 is a diagram representing the states of a voice activity detection automaton
- FIG. 5 is a graph illustrating the variations of a degree of vocal activity
- - Figure 6 is a block diagram of a noise overestimation module of the system of Figure 1
- FIG. 7 is a graph illustrating the calculation of a masking curve
- FIG. 8 is a graph illustrating the use of the masking curves in the system of FIG. 1.
- the denoising system shown in FIG. 1 processes a digital speech signal s.
- a windowing module 10 puts this signal s in the form of successive windows or frames, each consisting of a number N of digital signal samples. Conventionally, these frames can have mutual overlaps.
- N 25 ⁇ samples at a sampling frequency F of 8 kHz, with a weighting of
- the signal frame is transformed in the frequency domain by a module 11 applying a conventional fast Fourier transform (TFR) algorithm to calculate the module of the signal spectrum.
- TFR fast Fourier transform
- the frequency resolution available at the output of the fast Fourier transform is not used, but a lower resolution, determined by a number I of frequency bands covering the band [ 0, F / 2] of the signal.
- This division into frequency bands can be uniform (f (î) -f ( ⁇ -l) ⁇ F / 2I). It can also be non-uniform
- a module 12 calculates the respective averages of the spectral components S nf of the speech signal in bands, for example by a uniform weighting such that:
- the averaged spectral components S_ are addressed to a module 15 for detecting voice activity and to a module 16 for estimating noise.
- modules 15 and 16 can correspond to the flowcharts represented in FIGS. 2 and 3.
- the module 15 proceeds a priori to denoising the speech signal in the different bands i for the signal frame n.
- This a priori denoising is carried out according to a conventional process of non-linear spectral subtraction from noise estimates obtained during one or more previous frames.
- the module 15 calculates, with the resolution of the bands i, the frequency response Hp n ⁇ of the a priori denoising filter, according to the formula:
- ⁇ nj _ is a noise overestimation coefficient, the determination of which will be explained below.
- ⁇ p is a floor coefficient close to 0, conventionally used to avoid that the spectrum of the noise signal takes negative or too low values which would cause musical noise.
- Steps 17 to 20 therefore essentially consist in subtracting an estimate from the signal spectrum, increased by the coefficient ⁇ n _ ⁇ ⁇ 2 'of the noise spectrum estimated a priori.
- step 21 the module 15 calculates the energy of the a priori denoised signal in the different bands i
- the module 15 calculates, for each band i (O ⁇ i ⁇ I), a quantity 1 representing the short-term variation of the energy of the noise-suppressed signal in band i, as well as a long-term value E n -_ of the energy of the noise-suppressed signal in band i.
- the quantity ⁇ E, I_I, X can be calculated by a simplified formula of
- step 25 the quantity ⁇ E, n_, x is compared to a threshold ⁇ l. If the threshold ⁇ l is not reached, the counter b is incremented by one unit in step 26.
- step 27 the long-term estimator ba is compared to the value of the smoothed energy E nx . If ba ⁇ E nx , the estimator ba is taken equal to the smoothed value E n in step 28, and the counter b is reset to zero. The quantity p, which is taken equal to the ratio ba / E nx (step 36), is then equal to 1. If step 27 shows that ba ⁇ E nx , the counter b is compared with a limit value bmax at l step 29.
- step 28 the internal estimator bi is calculated in step 33 according to:
- the long-term estimator ba is updated with the value of the internal estimator bi in step 35. Otherwise, the long-term estimator ba remains unchanged. This avoids that sudden variations due to a speech signal lead to an update of the noise estimator.
- the module 15 After having obtained the quantities p, the module 15 proceeds to the voice activity decisions in step 37.
- the module 15 first updates the state of the detection automaton according to the quantity p Q calculated for the entire signal band.
- the new state ⁇ of the automaton depends on the previous state ⁇ x and on p Q , as shown in the figure.
- the module 15 also calculates the degrees of vocal activity ⁇ _ II, 1 • in each band i ⁇ l.
- This degree i • is preferably a non-binary parameter, that is to say that the function ⁇ XX / is a function continuously varying between 0 and 1 depending on the values taken by the quantity p •. This function has for example the appearance shown in FIG. 5.
- the module 16 calculates the noise estimates per band, which will be used in the denoising process, using the successive values of the components - and degrees of vocal activity ⁇ XI X •.
- step 42 the module 16 updates the noise estimates per band according to the formulas:
- ⁇ ⁇ denotes a forgetting factor such as 0 ⁇ ⁇ ⁇ l.
- the formula (6) highlights the taking into account of the degree of non binary vocal activity ⁇ ⁇ Il, 1.
- the long-term noise estimates B n ⁇ are overestimated by a module 45 (FIG. 1), before proceeding to denoising by nonlinear spectral subtraction.
- Module 45 calculates the overestimation coefficient ⁇ n ⁇ previously
- the increased estimate B n is obtained by combining the long-term estimate B_. . and an
- this combination is essentially a simple sum made by an adder 46. It could also be a weighted sum.
- the overestimation coefficient C n ⁇ is equal to
- the AS 1 TM measurement 1, 3 -1. of the noise variability reflects the variance of the noise estimator. It is obtained as a function of the values of S_ 11, / _ ⁇ 1_ and of BL n lfd- calculated for a certain number of previous frames on which the speech signal does not present any vocal activity in the
- band i It is a function of the deviations 3 nk, ⁇ B nk, ⁇ calculated for a number K of frames of silence (nk ⁇ n). In the example shown, this function is simply the maximum (block 50). For each frame n, the degree of vocal activity 1 ⁇ is compared to a threshold (block 51)
- ⁇ II, 1 does not exceed the threshold (which can be equal to 0 if the function g () has the form of FIG. 5), the FIFO 54 is not supplied, while it is in the opposite case.
- the maximum value contained in FIFO 54 is then provided as a measure of variability AB 1 TM 1, a -L.
- the measure of variability may alternatively be obtained as a function of the values S_ Xi. ff J_ (and not S, Xi f 1) and B n _. We then proceed in the same way, except that the FIFO
- the enhanced estimator B n provides excellent robustness to the musical noises of the denoising process.
- a first phase of the spectral subtraction is carried out by the module 55 shown in FIG. 1. This pnase provides, with the resolution of the bands i
- H i max S, s n, ⁇ _ n, ⁇ - B n, ⁇ ' ⁇ _r B n, ⁇ Lf (7)
- the coefficient ⁇ ⁇ represents, like the coefficient ⁇ p - of formula (3), a floor conventionally used to avoid negative or too low values of the denoised signal.
- this function being decreasing based on the estimated signal-to-noise ratio.
- This function is then equal to ⁇ n ⁇ for the lowest values of the signal-to-noise ratio. Indeed, when the signal is very noisy, it is a priori not useful to reduce the overestimation factor.
- this function decreases towards zero for the highest values of the signal / noise ratio. This protects the most energetic areas of the spectrum, where the speech signal is most significant, the amount subtracted from the signal then tending towards zero.
- a second denoising phase is carried out by a module 56 for protecting harmonics.
- This module calculates, with the resolution of the Fourier transform, the frequency response H n of a second filter of
- the module 57 can apply any known method of analysis of the speech signal of the frame to determine the period T, expressed as an integer or fractional number of samples, for example a linear prediction method.
- the protection provided by the module 56 may consist in carrying out, for each frequency f belonging to a band i: 'n, ⁇ - an, ⁇ n, x> 3Î- B n, ⁇ (8) and 3 ⁇ integer / f - ⁇ . f ⁇ ⁇ Af I 2 (9)
- This protection strategy is preferably applied for each of the frequencies closest to the harmonics of f, that is to say for any integer ⁇ .
- ⁇ f the frequency resolution with which the analysis module 57 produces the estimated tone frequency f, that is to say that the actual tone frequency is between f - ⁇ f / 2 and f + ⁇ f / 2
- the difference between the ⁇ -th harmonic of the real tonal frequency is its estimate ⁇ x D (condition (9)) can go up to ⁇ ⁇ x ⁇ f / 2.
- this difference can be greater than the spectral half-resolution ⁇ f / 2 of the Fourier transform.
- H n f can be equal to 1 as indicated above, which corresponds to the subtraction of a zero quantity within the framework of spectral subtraction, that is to say a complete protection of the frequency in question. More generally, this corrected frequency response H n 2 f could be taken equal to a value
- the spectral components S n f of a denoised signal are calculated by a multiplier 58:
- This signal S n f is supplied to a module 60 which calculates, for each frame n, a masking curve by applying a psychoacoustic model of auditory perception by the human ear.
- the masking phenomenon is a known principle of the functioning of the human ear. When two frequencies are heard simultaneously, one of them may no longer be heard. We then say that it is masked.
- M n, q C n, q R q ⁇ 12 > where R depends on the more or less voiced character of the signal.
- ⁇ denotes a degree of voicing of the speech signal, varying between zero (no voicing) and
- the parameter ⁇ can be of the known form:
- the denoising system also includes a module 62 which corrects the frequency response of the denoising, as a function of the masking curve Mn, q calculated by the module 60 and increased estimates B_,, calculated by the module 45.
- the module 62 decides the level of denoising which must really be achieved. By comparing the envelope of the estimate increased by the noise with the envelope formed by the masking thresholds Ix n, q, it is decided to denoise the signal only
- the new response H n f r for a frequency f belonging to the band i defined by the module 12 and to the bark band q thus depends on the relative difference between the increased estimate B nl of the corresponding spectral component of the noise and the masking curve Mn, q, as follows:
- the quantity subtracted from a spectral component S n f, in the process of spectral subtraction having the frequency response r is substantially equal to the minimum between on the one hand the quantity subtracted from this spectral component in the process of spectral subtraction having the frequency response H n f ' and on the other hand the fraction of
- FIG. 8 illustrates the principle of the correction applied by the module 62. It schematically shows a example of a masking curve M effetn, q_. calculated on the basis
- the quantity finally subtracted from the components S f will be that represented by the hatched areas, that is to say limited to the fraction of the increased estimate B n • of the spectral components of the noise which exceeds the masking curve.
- a module 65 reconstructs the denoised signal in the time domain, by operating the inverse fast Fourier transform (TFRI) inverse of the samples of frequency S n ⁇ delivered by the multiplier
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9711640 | 1997-09-18 | ||
FR9711640A FR2768544B1 (fr) | 1997-09-18 | 1997-09-18 | Procede de detection d'activite vocale |
PCT/FR1998/001979 WO1999014737A1 (fr) | 1997-09-18 | 1998-09-16 | Procede de detection d'activite vocale |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1016071A1 true EP1016071A1 (fr) | 2000-07-05 |
EP1016071B1 EP1016071B1 (fr) | 2002-01-16 |
Family
ID=9511227
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98943998A Expired - Lifetime EP1016071B1 (fr) | 1997-09-18 | 1998-09-16 | Procede et dispositif de detection d'activite vocale |
Country Status (7)
Country | Link |
---|---|
US (1) | US6658380B1 (fr) |
EP (1) | EP1016071B1 (fr) |
AU (1) | AU9168898A (fr) |
CA (1) | CA2304012A1 (fr) |
DE (1) | DE69803202T2 (fr) |
FR (1) | FR2768544B1 (fr) |
WO (1) | WO1999014737A1 (fr) |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2797343B1 (fr) * | 1999-08-04 | 2001-10-05 | Matra Nortel Communications | Procede et dispositif de detection d'activite vocale |
GB2367467B (en) | 2000-09-30 | 2004-12-15 | Mitel Corp | Noise level calculator for echo canceller |
GB2384670B (en) * | 2002-01-24 | 2004-02-18 | Motorola Inc | Voice activity detector and validator for noisy environments |
AUPS102902A0 (en) * | 2002-03-13 | 2002-04-11 | Hearworks Pty Ltd | A method and system for reducing potentially harmful noise in a signal arranged to convey speech |
JP4601970B2 (ja) * | 2004-01-28 | 2010-12-22 | 株式会社エヌ・ティ・ティ・ドコモ | 有音無音判定装置および有音無音判定方法 |
JP4490090B2 (ja) * | 2003-12-25 | 2010-06-23 | 株式会社エヌ・ティ・ティ・ドコモ | 有音無音判定装置および有音無音判定方法 |
US8788265B2 (en) * | 2004-05-25 | 2014-07-22 | Nokia Solutions And Networks Oy | System and method for babble noise detection |
KR100714721B1 (ko) * | 2005-02-04 | 2007-05-04 | 삼성전자주식회사 | 음성 구간 검출 방법 및 장치 |
EP1861846B1 (fr) * | 2005-03-24 | 2011-09-07 | Mindspeed Technologies, Inc. | Extension adaptative de mode vocal pour un detecteur d'activite vocale |
US20060241937A1 (en) * | 2005-04-21 | 2006-10-26 | Ma Changxue C | Method and apparatus for automatically discriminating information bearing audio segments and background noise audio segments |
US8126706B2 (en) * | 2005-12-09 | 2012-02-28 | Acoustic Technologies, Inc. | Music detector for echo cancellation and noise reduction |
US7366658B2 (en) * | 2005-12-09 | 2008-04-29 | Texas Instruments Incorporated | Noise pre-processor for enhanced variable rate speech codec |
GB0703275D0 (en) * | 2007-02-20 | 2007-03-28 | Skype Ltd | Method of estimating noise levels in a communication system |
CN101981612B (zh) * | 2008-09-26 | 2012-06-27 | 松下电器产业株式会社 | 声音分析装置以及声音分析方法 |
US20130282372A1 (en) * | 2012-04-23 | 2013-10-24 | Qualcomm Incorporated | Systems and methods for audio signal processing |
US9363603B1 (en) | 2013-02-26 | 2016-06-07 | Xfrm Incorporated | Surround audio dialog balance assessment |
Family Cites Families (15)
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US3840708A (en) * | 1973-07-09 | 1974-10-08 | Itt | Arrangement to test a tasi communication system |
US4281218A (en) * | 1979-10-26 | 1981-07-28 | Bell Telephone Laboratories, Incorporated | Speech-nonspeech detector-classifier |
US4277645A (en) * | 1980-01-25 | 1981-07-07 | Bell Telephone Laboratories, Incorporated | Multiple variable threshold speech detector |
US5212764A (en) | 1989-04-19 | 1993-05-18 | Ricoh Company, Ltd. | Noise eliminating apparatus and speech recognition apparatus using the same |
DE4012349A1 (de) * | 1989-04-19 | 1990-10-25 | Ricoh Kk | Einrichtung zum beseitigen von geraeuschen |
AU633673B2 (en) | 1990-01-18 | 1993-02-04 | Matsushita Electric Industrial Co., Ltd. | Signal processing device |
EP0459362B1 (fr) | 1990-05-28 | 1997-01-08 | Matsushita Electric Industrial Co., Ltd. | Processeur de signal de parole |
US5469087A (en) | 1992-06-25 | 1995-11-21 | Noise Cancellation Technologies, Inc. | Control system using harmonic filters |
US5742927A (en) * | 1993-02-12 | 1998-04-21 | British Telecommunications Public Limited Company | Noise reduction apparatus using spectral subtraction or scaling and signal attenuation between formant regions |
JP3685812B2 (ja) * | 1993-06-29 | 2005-08-24 | ソニー株式会社 | 音声信号送受信装置 |
US5657422A (en) * | 1994-01-28 | 1997-08-12 | Lucent Technologies Inc. | Voice activity detection driven noise remediator |
US5555190A (en) | 1995-07-12 | 1996-09-10 | Micro Motion, Inc. | Method and apparatus for adaptive line enhancement in Coriolis mass flow meter measurement |
US5774837A (en) * | 1995-09-13 | 1998-06-30 | Voxware, Inc. | Speech coding system and method using voicing probability determination |
US5659622A (en) * | 1995-11-13 | 1997-08-19 | Motorola, Inc. | Method and apparatus for suppressing noise in a communication system |
FI100840B (fi) * | 1995-12-12 | 1998-02-27 | Nokia Mobile Phones Ltd | Kohinanvaimennin ja menetelmä taustakohinan vaimentamiseksi kohinaises ta puheesta sekä matkaviestin |
-
1997
- 1997-09-18 FR FR9711640A patent/FR2768544B1/fr not_active Expired - Fee Related
-
1998
- 1998-09-16 US US09/509,150 patent/US6658380B1/en not_active Expired - Lifetime
- 1998-09-16 DE DE69803202T patent/DE69803202T2/de not_active Expired - Fee Related
- 1998-09-16 EP EP98943998A patent/EP1016071B1/fr not_active Expired - Lifetime
- 1998-09-16 CA CA002304012A patent/CA2304012A1/fr not_active Abandoned
- 1998-09-16 AU AU91688/98A patent/AU9168898A/en not_active Abandoned
- 1998-09-16 WO PCT/FR1998/001979 patent/WO1999014737A1/fr active IP Right Grant
Non-Patent Citations (1)
Title |
---|
See references of WO9914737A1 * |
Also Published As
Publication number | Publication date |
---|---|
EP1016071B1 (fr) | 2002-01-16 |
CA2304012A1 (fr) | 1999-03-25 |
FR2768544B1 (fr) | 1999-11-19 |
US6658380B1 (en) | 2003-12-02 |
DE69803202T2 (de) | 2002-08-29 |
DE69803202D1 (de) | 2002-02-21 |
AU9168898A (en) | 1999-04-05 |
WO1999014737A1 (fr) | 1999-03-25 |
FR2768544A1 (fr) | 1999-03-19 |
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