WO2000039991A1 - Methods and apparatus for adaptive signal gain control in communications systems - Google Patents
Methods and apparatus for adaptive signal gain control in communications systems Download PDFInfo
- Publication number
- WO2000039991A1 WO2000039991A1 PCT/SE1999/002288 SE9902288W WO0039991A1 WO 2000039991 A1 WO2000039991 A1 WO 2000039991A1 SE 9902288 W SE9902288 W SE 9902288W WO 0039991 A1 WO0039991 A1 WO 0039991A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- gain
- level
- adaptive
- output signal
- analog
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/02—Constructional features of telephone sets
- H04M1/19—Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M9/00—Arrangements for interconnection not involving centralised switching
- H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
- H04M9/082—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic using echo cancellers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M9/00—Arrangements for interconnection not involving centralised switching
- H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
Definitions
- the present invention relates to communications systems, and more particularly, to adaptive gain control in communications systems.
- signal level adjustment is left to the application user or is made automatically based on calibration performed when the application is first installed or is first used. For example, a user is often instructed to make gain control adjustments on a multimedia computer soundboard so that a line-in or microphone signal is properly processed for transmission. Alternatively, the user can be instructed to provide a calibration signal (e.g., by speaking into a microphone or providing an audio line-in signal) upon application installation and setup, so that the soundboard gain can be automatically set.
- a calibration signal e.g., by speaking into a microphone or providing an audio line-in signal
- the present invention fulfills the above-described and other needs by providing techniques for adaptive gain control.
- the disclosed techniques provide correctly adjusted signal levels during the entirety of a conversation and are resilient to background noise and loudspeaker echo. Further, the disclosed techniques can account for multiple near-end speakers, as well as changes in near-end environment (e.g., changes in user and microphone position).
- An exemplary adaptive gain controller according to the invention includes a gain control processor configured to adjust an analog gain applied to a microphone output signal based on measurements of the microphone output signal and on measurements of a loudspeaker input signal. For example, the analog gain can be adjusted based on estimates of the average and peak speech levels in the microphone signal and on a determination of whether the microphone output signal is saturated.
- the analog gain is adjusted such that the average speech level in the microphone output signal approaches a target average level and such that the peak speech level in the microphone output signal does not exceed a maximum peak level.
- the average and peak speech level estimates are updated, in exemplary embodiments, only when voice activity detectors indicate that the microphone output signal includes speech and that the loudspeaker input signal does not include speech.
- An exemplary method for adjusting the analog gain applied to a signal prior to digitization via an analog-to-digital converter includes the steps of: determining whether a digital output of the analog-to-digital converter is saturated; decreasing the analog gain if the digital output is saturated; comparing a measured average level of the communications signal to a target average level if the digital output is not saturated; decreasing the analog gain if the measured average level is too far above the target average level; comparing a measured peak level of the communications signal to a maximum peak level of the communications signal if the measured average level is too far below the target average level; and increasing the analog gain if the measured peak level is below the maximum level.
- Figure 1 is a block diagram of a communications system incorporating an exemplary adaptive gain control arrangement according to the invention.
- Figure 2 is a flow diagram depicting steps in an exemplary method of adaptive gain control according to the invention.
- FIG. 1 depicts an exemplary Internet telephony system 100 incorporating an adaptive gain control arrangement according to the invention.
- a system can be included, for example, in a multimedia personal computer.
- Those of skill in the art will appreciate that the below described functionality of the various elements of the system 100 of Figure 1 can be implemented using known analog and digital signal processing hardware and/or a general purpose digital computer.
- the exemplary system 100 includes a microphone 110, a loudspeaker 120, an adjustable-gain amplifier 130, an analog-to-digital converter 140, a digital-to-analog converter 145, first and second voice activity detectors (NADs) 150, 155, and a control processor 160.
- a far-end digital signal x( ) (e.g., digitized far-end speech and noise received via the Internet) is input to the digital- to-analog converter 145 and to the second voice activity detector 155.
- the digital- to-analog converter 145 converts the far-end signal x(n) to the analog domain, and the resulting far-end analog signal x(f) is input to the loudspeaker 120 for presentation to a near-end user (not shown). Additionally, near-end speech v,(t), near-end noise v 2 (t) and far-end echo s(t) are received at the microphone 110 and combine to produce a near-end analog signal y(f) which is amplified by the adjustable gain amplifier 130 and digitized by the analog-to-digital converter 140.
- the resulting digital near-end signal y(n) is input to the first voice activity detector 150 and to the control processor 160, and is also passed on to the far-end (e.g., via the Internet). Output from each voice activity detector 150, 155 is input to the control processor 160.
- control processor 160 monitors the near-end digital signal y(n), as well as the output from each voice activity detector 150, 155, and adjusts the gain of the amplifier 130 so that the level of the near-end digital signal y( ⁇ ) is suitable for input to a speech coder (not shown) and/or any other digital signal processing algorithm which may be used to prepare the near-end signal y(n) for transmission.
- a speech coder not shown
- any other digital signal processing algorithm which may be used to prepare the near-end signal y(n) for transmission.
- control processor 160 measures the average level of near- end speech in the near-end signal y(n) and adjusts the gain of the amplifier 130 so as to continually push the measured average level toward a target, or preferred average level (e.g., -22dBoV, as defined in the Subscriber Loop Signaling and Transmission Handbook, Whitman D. Reeve, IEEE Press, 1992, pp. 95-97).
- a target or preferred average level (e.g., -22dBoV, as defined in the Subscriber Loop Signaling and Transmission Handbook, Whitman D. Reeve, IEEE Press, 1992, pp. 95-97).
- gain adjustments can be conditioned, as is described in detail below, on the outputs of the voice activity detectors 150, 155 and on a test for signal saturation.
- gain adjustments can also be conditioned on a measurement of the peak level of the near-end speech in order to prevent gain adjustment errors when two or more near-end users are speaking.
- a running estimate of the average level of near-end speech in the near-end signal y(n) is updated at the end of each of a succession of near-end signal sample blocks (e.g., at the end of each 160-sample GSM speech frame).
- the estimate of the average near- end speech level is updated only when the first voice activity detector 150 indicates that the near-end signal y(n) includes speech.
- the estimate is updated only when the second voice activity detector 155 indicates that the far-end signal x(n) does not include speech.
- Techniques for constructing the voice activity detectors 150, 155 are well known and are described, for example, in ETSI, GSM 06:32, European Digital Cellular Telecommunication System Voice Activity Detection, Version 4.3.1, April 1998.
- the running estimate of the average near-end speech level is updated at the end of each block of samples (e.g., at the end of each GSM frame) by first computing an average level r y of the overall near-end signal y(n) for the block of samples.
- the average near-end signal level r y is computed as:
- the near-end speech level for the frame is computed by subtracting an estimate of the near-end noise level (which can be computed during periods of no near-end speech and no far-end speech, as indicated by the voice activity detectors 150, 155) from the computed near-end signal level.
- the near-end speech level r vl is computed as the difference between the near-end signal level r y and the noise level r v2 :
- the running estimate of the average near-end speech level r av is updated by smoothing from frame to frame.
- the average level estimate r v is updated as: ar av + (1 - ⁇ ) ⁇ ;
- ⁇ is an update coefficient (a real number) set to provide a balance between speed of gain adaptation and system stability.
- Empirical studies have shown that 0.995 is a suitable value for the update coefficient a.
- periodic amplifier gain adjustments can be made to keep the average near-end speech level at or near the target level (e.g., within a range of values around the target level). For example, the gain can be incrementally adjusted every several blocks (e.g., every 30 to 50 GSM frames) based on a comparison of the running average estimate r av and the target value (e.g., -22dBoV).
- the amplifier gain can be stepped down or up by an appropriate amount (e.g., l-3dB).
- an appropriate amount e.g., l-3dB.
- the above described technique provides quality gain control when only one near-end user is present, it can yield unsatisfactory results when multiple near-end users are speaking.
- the above described average level estimate will incorporate all of the voice levels and can thus lead to over-amplification and clipping when the loudest user(s) are speaking.
- another exemplary embodiment solves this problem by considering the peak level of the near-end speech. Specifically, a running estimate of the peak near-end speech level is computed in block- wise fashion as:
- ⁇ is a real update coefficient (e.g., 0.995)
- the speech level for a frame r vl is computed as described above.
- the peak level estimate r peak is updated only when the voice activity detectors 150, 155 indicate a near-end single talk condition.
- a target value e.g., -16dBoV
- the control processor 160 can be configured to permit gain increases (as indicated by the average level estimate) only when the peak level estimate is below the target peak level.
- the above described gain control techniques can be made still more robust by considering saturation of the analog-to-digital converter 140.
- gain increases are permitted only when the converter 140 is not saturated (as indicated, for example, when the output signal y(n) has a value equal to the minimum or maximum of the converter output range), or if the gain is decreased whenever saturation is detected, then signal clipping and the resulting distortion can be minimized.
- saturation is monitored by maintaining a running saturation counter.
- the number of saturated samples L in the block or frame is determined (e.g., samples having the minimum or maximum converter output value are counted). If the number of saturated samples L in the block or frame is greater than or equal to a per-block saturation threshold Tl (e.g., 2), then the saturation counter is incremented by the number of saturated samples L. However, if the number of saturated samples L in the block or frame is less than the per-block threshold Tl, then the saturation counter is decreased by a predetermined amount M (e.g, an integer in the range 1-5).
- Tl per-block saturation threshold
- an overall saturation threshold T2 e.g., 50
- the amplifier gain is stepped down, and the saturation counter is reset.
- the amplifier gain is adjusted in some suitable fashion (e.g., based on the above described average and peak level estimates).
- consecutive saturated samples can be assigned a larger weight (e.g., 2) as compared to single saturated samples (since a single saturation sample may be inaudible, while consecutive saturated samples are often disturbing to a receiving user).
- effective gain control can be accomplished, according to the invention, by making gain adjustment decisions based on any combination of the above described average, peak and saturation parameters.
- An exemplary decision algorithm 200 is depicted in Figure 2. The exemplary algorithm can be used, for example, to make amplifier gain adjustments once every several (e.g., 30-50) frames (where it is understood that the above described average level estimate, peak level estimate and saturation counter are updated at the end of each frame).
- the decision algorithm begins at step 210, and at step 220 a determination is made whether the amplified and digitized signal y(n) is saturated (e.g., whether the running saturation counter is greater than the saturation threshold T2). If so, then the amplifier gain is decreased (e.g., by l-3dB) at step 230, and the decision algorithm is complete at step 240. If not, then a determination is made (at step 250) whether the signal level is too high (e.g., whether the average speech level estimate is too far above the target average level). If so, then the amplifier gain is decreased at step 230, and the decision algorithm is complete at step 240.
- the signal level is too high (e.g., whether the average speech level estimate is too far above the target average level). If so, then the amplifier gain is decreased at step 230, and the decision algorithm is complete at step 240.
- the signal level is too low (e.g., whether the average speech level estimate is too far below the target average level). If not, then the amplifier gain is not modified, and the decision algorithm is complete at step 240. If so, then a determination is made (at step 270) whether the peak signal level is within an appropriate range (e.g., whether the peak speech level estimate is
- the disclosed gain control techniques provide correctly adjusted signal levels during the entirety of a conversation and are resilient to background noise and loudspeaker echo. Further, the disclosed techniques can account for multiple near-end speakers, as well as changes in the near-end environment (e.g., changes in user and microphone position).
- the disclosed techniques can be made to work in conjunction with other adaptive signal processing algorithms, such as noise suppression algorithms and/or adaptive-filter echo canceling algorithms.
- other adaptive signal processing algorithms such as noise suppression algorithms and/or adaptive-filter echo canceling algorithms.
- echo cancelers use an adaptive algorithm
- Least Mean Squares e.g., Least Mean Squares, or Normalized Least Mean Squares
- gain changes made using the above described techniques can be reported directly to such an echo canceler so that the adaptive filter coefficients of the echo canceler can be adjusted immediately. As a result, the echo canceler will not require additional time to adapt to level changes introduced by the above described techniques.
- the resulting signal delay i.e., the time required for analog gain changes at the amplifier 130 to be reflected in the output signal y(n)
- the echo canceler or other adaptive algorithm
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69937613T DE69937613T2 (en) | 1998-12-23 | 1999-12-07 | METHOD AND DEVICE FOR ADAPTIVE SIGNAL AMPLIFICATION CONTROL IN COMMUNICATION SYSTEMS |
JP2000591777A JP4204754B2 (en) | 1998-12-23 | 1999-12-07 | Method and apparatus for adaptive signal gain control in a communication system |
EP99965628A EP1142288B1 (en) | 1998-12-23 | 1999-12-07 | Methods and apparatus for adaptive signal gain control in communications systems |
KR1020017008044A KR20010099924A (en) | 1998-12-23 | 1999-12-07 | Methods and apparatus for adaptive signal gain control in communicatons systems |
CA002356620A CA2356620A1 (en) | 1998-12-23 | 1999-12-07 | Methods and apparatus for adaptive signal gain control in communications systems |
AU21321/00A AU2132100A (en) | 1998-12-23 | 1999-12-07 | Methods and apparatus for adaptive signal gain control in communications systems |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/219,517 | 1998-12-23 | ||
US09/219,517 US20030091180A1 (en) | 1998-12-23 | 1998-12-23 | Adaptive signal gain controller, system, and method |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2000039991A1 true WO2000039991A1 (en) | 2000-07-06 |
Family
ID=22819594
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1999/002288 WO2000039991A1 (en) | 1998-12-23 | 1999-12-07 | Methods and apparatus for adaptive signal gain control in communications systems |
Country Status (10)
Country | Link |
---|---|
US (1) | US20030091180A1 (en) |
EP (1) | EP1142288B1 (en) |
JP (1) | JP4204754B2 (en) |
KR (1) | KR20010099924A (en) |
CN (1) | CN1331883A (en) |
AU (1) | AU2132100A (en) |
CA (1) | CA2356620A1 (en) |
DE (1) | DE69937613T2 (en) |
TW (1) | TW453098B (en) |
WO (1) | WO2000039991A1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1345336A1 (en) * | 2002-03-11 | 2003-09-17 | Alcatel | Automatic gain control method for echo attenuation |
WO2004077806A1 (en) * | 2003-02-27 | 2004-09-10 | Telefonaktiebolaget Lm Ericsson (Publ) | Audibility enhancement |
FR2888458A1 (en) * | 2005-07-11 | 2007-01-12 | France Telecom | METHOD AND DEVICE FOR TAKING SOUND, IN PARTICULAR IN HANDS-FREE TELEPHONE TERMINALS |
GB2437570A (en) * | 2006-04-26 | 2007-10-31 | Zarlink Semiconductor Inc | Automatic gain control for mobile microphone and echo canceller |
US8135148B2 (en) | 2006-04-26 | 2012-03-13 | Microsemi Semiconductor Corp. | Automatic gain control for mobile microphone |
WO2012052675A1 (en) * | 2010-10-22 | 2012-04-26 | France Telecom | Stabilisation of the amplification gain of a microphone signal in a telephony apparatus |
US20230412727A1 (en) * | 2022-06-20 | 2023-12-21 | Motorola Mobility Llc | Adjusting Transmit Audio at Near-end Device Based on Background Noise at Far-end Device |
Families Citing this family (15)
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US6012027A (en) * | 1997-05-27 | 2000-01-04 | Ameritech Corporation | Criteria for usable repetitions of an utterance during speech reference enrollment |
US6363127B1 (en) * | 1999-06-23 | 2002-03-26 | At&T Wireless Services, Inc. | Automatic gain control methods and apparatus suitable for use in OFDM receivers |
JP2003280691A (en) * | 2002-03-19 | 2003-10-02 | Sanyo Electric Co Ltd | Voice processing method and voice processor |
US20060062407A1 (en) * | 2004-09-22 | 2006-03-23 | Kahan Joseph M | Sound card having feedback calibration loop |
CN100369113C (en) * | 2004-12-31 | 2008-02-13 | 中国科学院自动化研究所 | Method for adaptively improving speech recognition rate by means of gain |
US20060217066A1 (en) * | 2005-03-25 | 2006-09-28 | Siemens Communications, Inc. | Wireless microphone system |
EP1729410A1 (en) * | 2005-06-02 | 2006-12-06 | Sony Ericsson Mobile Communications AB | Device and method for audio signal gain control |
JP2008172484A (en) * | 2007-01-11 | 2008-07-24 | Pioneer Electronic Corp | Handsfree device |
CN101067927B (en) * | 2007-04-19 | 2010-11-10 | 北京中星微电子有限公司 | Sound volume adjusting method and device |
CN102904538B (en) * | 2012-10-10 | 2015-02-04 | 华平信息技术股份有限公司 | Automatic gain control (AGC)-based gain parameter adjustment method of audio analog signal |
TWI505724B (en) | 2013-06-10 | 2015-10-21 | Princeton Technology Corp | Gain controlling system, sound playback system, and gain controlling method thereof |
GB2547459B (en) * | 2016-02-19 | 2019-01-09 | Imagination Tech Ltd | Dynamic gain controller |
US11223716B2 (en) * | 2018-04-03 | 2022-01-11 | Polycom, Inc. | Adaptive volume control using speech loudness gesture |
CN108900171A (en) * | 2018-07-23 | 2018-11-27 | 上海亮牛半导体科技有限公司 | A kind of AGC device and method being adapted to zero intermediate frequency radio-frequency transmitter |
WO2021248350A1 (en) | 2020-06-10 | 2021-12-16 | Qualcomm Incorporated | Audio gain selection |
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1998
- 1998-12-23 US US09/219,517 patent/US20030091180A1/en not_active Abandoned
-
1999
- 1999-12-07 KR KR1020017008044A patent/KR20010099924A/en not_active Application Discontinuation
- 1999-12-07 CA CA002356620A patent/CA2356620A1/en not_active Abandoned
- 1999-12-07 CN CN99814894A patent/CN1331883A/en active Pending
- 1999-12-07 WO PCT/SE1999/002288 patent/WO2000039991A1/en active IP Right Grant
- 1999-12-07 DE DE69937613T patent/DE69937613T2/en not_active Expired - Lifetime
- 1999-12-07 EP EP99965628A patent/EP1142288B1/en not_active Expired - Lifetime
- 1999-12-07 JP JP2000591777A patent/JP4204754B2/en not_active Expired - Lifetime
- 1999-12-07 AU AU21321/00A patent/AU2132100A/en not_active Abandoned
- 1999-12-23 TW TW088122761A patent/TW453098B/en not_active IP Right Cessation
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US4700382A (en) * | 1986-03-03 | 1987-10-13 | American Telephone And Telegraph Company, At&T Information Systems, Inc. | Voice-switched telephone circuit with center idle state |
US5668871A (en) * | 1994-04-29 | 1997-09-16 | Motorola, Inc. | Audio signal processor and method therefor for substantially reducing audio feedback in a cummunication unit |
EP0739123A2 (en) * | 1995-04-19 | 1996-10-23 | Nec Corporation | Communication unit with residual acoustic echo suppression and method for suppressing residual echoes |
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Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1345336A1 (en) * | 2002-03-11 | 2003-09-17 | Alcatel | Automatic gain control method for echo attenuation |
WO2004077806A1 (en) * | 2003-02-27 | 2004-09-10 | Telefonaktiebolaget Lm Ericsson (Publ) | Audibility enhancement |
US7092514B2 (en) | 2003-02-27 | 2006-08-15 | Telefonaktiebolaget Lm Ericsson (Publ) | Audibility enhancement |
FR2888458A1 (en) * | 2005-07-11 | 2007-01-12 | France Telecom | METHOD AND DEVICE FOR TAKING SOUND, IN PARTICULAR IN HANDS-FREE TELEPHONE TERMINALS |
WO2007006919A1 (en) * | 2005-07-11 | 2007-01-18 | France Telecom | Sound pick-up method and device for, in particular in handsfree telephone terminals |
US8064591B2 (en) | 2005-07-11 | 2011-11-22 | France Telecom | Sound pick-up method and device, in particular for handsfree telephone terminals |
GB2437570A (en) * | 2006-04-26 | 2007-10-31 | Zarlink Semiconductor Inc | Automatic gain control for mobile microphone and echo canceller |
GB2437570B (en) * | 2006-04-26 | 2010-04-07 | Zarlink Semiconductor Inc | Automatic gain control for mobile microphone |
US8135148B2 (en) | 2006-04-26 | 2012-03-13 | Microsemi Semiconductor Corp. | Automatic gain control for mobile microphone |
WO2012052675A1 (en) * | 2010-10-22 | 2012-04-26 | France Telecom | Stabilisation of the amplification gain of a microphone signal in a telephony apparatus |
FR2966671A1 (en) * | 2010-10-22 | 2012-04-27 | France Telecom | AMPLIFICATION GAIN STABILIZATION OF A MICROPHONE SIGNAL IN TELEPHONY EQUIPMENT. |
US20230412727A1 (en) * | 2022-06-20 | 2023-12-21 | Motorola Mobility Llc | Adjusting Transmit Audio at Near-end Device Based on Background Noise at Far-end Device |
Also Published As
Publication number | Publication date |
---|---|
CA2356620A1 (en) | 2000-07-06 |
KR20010099924A (en) | 2001-11-09 |
TW453098B (en) | 2001-09-01 |
DE69937613T2 (en) | 2008-10-23 |
EP1142288B1 (en) | 2007-11-21 |
AU2132100A (en) | 2000-07-31 |
JP4204754B2 (en) | 2009-01-07 |
US20030091180A1 (en) | 2003-05-15 |
EP1142288A1 (en) | 2001-10-10 |
JP2002534849A (en) | 2002-10-15 |
DE69937613D1 (en) | 2008-01-03 |
CN1331883A (en) | 2002-01-16 |
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