CN85100784A - Feedback acoustic suppressor - Google Patents
Feedback acoustic suppressor Download PDFInfo
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- CN85100784A CN85100784A CN 85100784 CN85100784A CN85100784A CN 85100784 A CN85100784 A CN 85100784A CN 85100784 CN85100784 CN 85100784 CN 85100784 A CN85100784 A CN 85100784A CN 85100784 A CN85100784 A CN 85100784A
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- feedback
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- feedback sound
- correlation function
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- Circuit For Audible Band Transducer (AREA)
Abstract
This invention belongs to adaptive electro acoustical signal treatment technology category.The acoustic feedback that the technical issues that need to address exist when being sound reinforcement system work.The major technique feature of this invention is coherent detection online and adaptive-filtering.This invention is applicable to aspects such as hall meeting-place public address, long distance communication, videoconference.
Description
This invention is applied to assembly hall public address aspect, belongs to the technology category that the adaptive electro acoustical signal is handled.
So-called feedback acoustic suppressor is exactly to utilize " the feedback sound " of artificial manufacturing and actual feedback sound to offset.And existing technology is:
1, the direct transmission between minimizing loud speaker and the microphone, wherein:
(1) utilizes directional microphone and sound column
(2) both positions of reasonable Arrangement, direction
This kind method is subjected to the restriction of original building design very big, and the acoustic pressure that improves only is 5～6db.
2, reduce raise one's voice and microphone between indirect communication, comprising:
(1) adopts sound-absorbing material
(2) the serious low-frequency range of excision diffraction
(3) reduce the reverberation time
This kind method is relatively more passive.
3, improve the scrambling of transmission response
Because the composite wave of primary sound and feedback sound and reflected sound is the comb frequencies characteristic; So, need 12～25 equalizers in order to eliminate this phenomenon, so method is very numerous in the easiest singing in peak value place.Traditional way that Here it is.
4, shift frequency method
Shift frequency be by with whole parallel moving of signal several～tens hertz, make the peak valley point of pectination frequency response alternately change, thereby improved the inhomogeneities of frequency response that this method can improve acoustic pressure 8db.Not enough is that frequency displacement makes music signal produce distortion, especially in low-frequency range, and can not suppress through feedback sound.However the shift frequency method is still comparatively effective method at present.
5, phase modulation method
In time ceaselessly the phase place of conditioning signal (frequency of modulation is
Hertz) equally also can improve the inhomogeneities of frequency response, this method distortion is less, can be used for music, and " Lie Sili effect " arranged, but the degree of improving is less, only improves the about 4db of acoustic pressure.(select from Shen
The 33rd page of the inhibition＞electroacoustic techniques of＜acoustic feedback and it 82 year first phase)
In sum; The shortcoming of prior art is:
(1) depends on the building construction design
(2) be subjected to the restriction (relative position, direction) of sound field
(3) degree of Gai Shaning is limited
(4) bring distortion to disturb
(5) design, layout, adjustment are wasted time and energy
The technical solution used in the present invention is different from above-mentioned method fully, but starts with from primary sound and separating of feedback sound, adopts the auto-adaptive filtering technique of correlation detection technology and rising in recent years.
Purpose of the present invention is intended to thoroughly eliminate acoustic feedback and singing that brings and interference.
Foundation of the present invention is:
(1) with the difference between primary sound and the feedback sound as distinguishing both objective base of identification.
(2) because primary sound and feedback sound are linear superposition in air, so the method that useable linear is subtracted each other is eliminated feedback sound.
The method that feedback sound is offset is, obtain the related parameter that has of each time feedback sound by related operation, and produce " pseudo-feedback sound " signal with these parameters, with the derived reference signal of this signal as sef-adapting filter, feedback sound and " pseudo-feedback sound " are approached in filter one by one, and final the realization offset.As shown.
The advantage of this method is:
(1) elimination of feedback sound is more thorough, can reach 30～40db.(the shift frequency method is about 10db, and phase-shifting method is about 4db)
(2) do not rely on architectural design
(3) restriction that not arranged by sound field
(4) not only singing can be eliminated, tonequality can also be improved.(eliminate regeneration and disturb coloration)
(5) need not manually adjust and to enter optimum Working automatically, be particularly suitable for the environment of frequent conversion
(6) can with existing sound reinforcement system " compatibility "
(7) can be generalized to aspects such as long distance communication, conference telephone
Description of drawings:
α is the time-delay of each link in the delay line
W is the weighing vector of sef-adapting filter
∑ is summation
-for subtracting each other
＞be amplifier
A/D is an analog-to-digital conversion
D/A is digital-to-analogue conversion
P is a microphone
As shown in the figure, the relevant part of input and output is analyzed, drawn optimum delay and proportionality coefficient, subtract each other again, and in subtracting each other, constantly adjust, till offsetting fully.
The best way of implementing is:
Adopt RAM as delay line, utilizing its high integration, but must note access speed, the place can not establish the peek pointer at no feedback sound.
For reducing operation times, adopt FFT to ask related algorithm.
In order to prevent erroneous judgement, when maximum appears in correlation function, to see also whether the correlation function of derivative separately maximum also occurs, come synthetic determination with the definition of fuzzy mathematics.
Cut off the public address main channel when debugging automatically, send into a pseudo-random signal, auto-correlation computation is become be computing cross-correlation.
Exchange the counteracting precision for to underspeed when test, then to sacrifice accuracy guarantee speed, associated period is got 30～50ms during work.
Arithmetic unit is preferably realized by hardware, and is high-speed to obtain.
Owing to have " ring " phenomenon near the maximum of correlation function, the maximum of also need and be close to when judging compares.
The convergence preferred design becomes speed variable, presses the method for least squares convergence.
For eliminating the additional interference that produces because of " neutralisation process ", add a recursion filter in addition.
Hasten to select format filter for use in order to add rapid convergence.
The frequency response of feedback factor is not a straight line, so will add compensation.Compensation is finished by sef-adapting filter is double.
The bandwidth of whole system will suit, correlation curve meeting " ring " when narrow, and what some Frequency point was just offset when wide is not thorough.
Under the nonrandom signal operating state, test calculating online with the method for statistics.
Claims (1)
- The correlation principle that the present invention is based on primary sound and feedback sound detects, thereby draws the related parameter that has of feedback sound, uses the feedback sound in the sef-adapting filter elimination compound voice then.Therefore the technology of asking for protection has:1, suppressing to use coherent detection aspect the acoustic feedback.2, suppressing to use sef-adapting filter aspect the acoustic feedback, promptly eliminate feedback sound with linear method of subtracting each other.3, when coherent detection, quote the notion of fuzzy mathematics, and use the correlation function of correlation function, first order derivative, the correlation function of second derivative simultaneously.4, filter is by the least square method convergence.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 85100784 CN85100784A (en) | 1985-04-01 | 1985-04-01 | Feedback acoustic suppressor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 85100784 CN85100784A (en) | 1985-04-01 | 1985-04-01 | Feedback acoustic suppressor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN85100784A true CN85100784A (en) | 1986-09-24 |
Family
ID=4791429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 85100784 Pending CN85100784A (en) | 1985-04-01 | 1985-04-01 | Feedback acoustic suppressor |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN85100784A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101273616B (en) * | 2005-09-01 | 2013-01-02 | 西门子企业通讯有限责任两合公司 | Method and apparatus for multiparty collaboration enhancement |
-
1985
- 1985-04-01 CN CN 85100784 patent/CN85100784A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101273616B (en) * | 2005-09-01 | 2013-01-02 | 西门子企业通讯有限责任两合公司 | Method and apparatus for multiparty collaboration enhancement |
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