CN102914591A - Method for measuring sound absorption coefficient by time delay - Google Patents
Method for measuring sound absorption coefficient by time delay Download PDFInfo
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- CN102914591A CN102914591A CN2012104064342A CN201210406434A CN102914591A CN 102914591 A CN102914591 A CN 102914591A CN 2012104064342 A CN2012104064342 A CN 2012104064342A CN 201210406434 A CN201210406434 A CN 201210406434A CN 102914591 A CN102914591 A CN 102914591A
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Abstract
The invention discloses a method for measuring sound absorption coefficient by time delay and belongs to the field of noises. The method includes: arranging a first microphone and a second microphone right ahead a sound absorption material needing to be measured, respectively measuring the reflection sound pressure P1 and P2 of two positions, and then computing according to the steps: (1) computing the Laplace transformation at the first microphone and the second microphone to obtain P1(S) and P2(S); (2) computing; (3) defining x(t) and y(t); (4) performing Laplace transformation for the x(t) and y(t) to obtain X(s) and Y(s); (5) performing Laplace transformation to obtain the reflection coefficient R of the sound absorption material; and (6) computing to obtain the sound absorption coefficient of the sound absorption material. Compared with the prior art, the method is positive and obvious in effect. The method is simple and rapid and overcomes the defects of sound absorption coefficient measurement of sound absorption materials by a traditional standing wave method and a traditional reverberation-chamber method.
Description
Technical field
The invention belongs to the noise field, be specifically related to a kind of measuring method of acoustic absorbant acoustical absorption coefficient.
Background technology
Sqouynd absorption lowering noise is to utilize acoustic absorbant or sound absorption structure to reduce noise.The mechanism of acoustic absorbant sound absorption is: when sound wave incided acoustic absorbant, because the damping action of acoustic absorbant, a part of sound wave was absorbed by acoustic absorbant and consumes, and a part of sound wave is reflected back.Therefore, acoustical absorption coefficient is defined as the ratio of the acoustic energy of acoustic energy that acoustic absorbant absorbs and incident acoustic wave.Traditional acoustical absorption coefficient measuring method mainly contains standing-wave-tube method and Reverberation room method.The measuring principle of standing-wave-tube method is: plane vertical incidence sound wave can form standing wave in standing wave tube, thereby maximal value and the minimum value of acoustic pressure occur, obtains the acoustical absorption coefficient of acoustic absorbant according to the ratio of the acoustic pressure maximal value that measures and minimum value.But the acoustical absorption coefficient of measuring acoustic absorbant with standing-wave-tube method exists some shortcomings, mainly contains: can cause error when the maximal value of the search acoustic pressure of popping one's head in and minimum value 1.; 2. can not immediately obtain the acoustical absorption coefficient of acoustic absorbant, need time-delay; 3. to measuring just helpless such as the husky acoustical absorption coefficient of discrete material that waits; 4. the size of acoustic absorbant sample will cooperate with the precision size of standing wave tube, otherwise will bring very large error.The principle that Reverberation room method is measured the acoustical absorption coefficient of acoustic absorbant is the acoustical absorption coefficient that obtains acoustic absorbant by measuring the reverberation time, but the acoustical absorption coefficient of measuring acoustic absorbant with Reverberation room method also exists some shortcomings, mainly contain: 1. difference is very large sometimes to the measured value of the acoustical absorption coefficient of same material for each reverberation chamber, causes measurement result not have comparability; 2. the size of acoustical absorption coefficient changes with material area and in the variation of indoor location etc., and these materials might be greater than 1 at the acoustical absorption coefficient of medium-high frequency section.
Summary of the invention
The objective of the invention is for above-mentioned the deficiencies in the prior art, provide a kind of simply, the method for time delay measurement acoustical absorption coefficient efficiently.
Technical scheme of the present invention is carried out in the following manner: a kind of method of time delay measurement acoustical absorption coefficient, at first arrange the first microphone and second microphone in the acoustic absorbant dead ahead that needs are measured, respectively the reflecting acoustic pressure P at two places, both sides
1And P
2, calculate according to following step afterwards:
(1) Laplace transformation at calculating the first microphone and second microphone place obtains P
1(S) and P
2(S);
(2) Laplace transformation of the reflection coefficient on calculating acoustic absorbant surface
(3) define x(t) and y(t);
(4) with x(t) and y(t) carry out Laplace transformation and obtain X(s) and Y(s);
(5) will
Carry out Laplace and change the reflection R that obtains acoustic absorbant;
(6) acoustical absorption coefficient of calculating acoustic absorbant
Distance between distance, second microphone and the acoustic absorbant between described the first microphone and the second microphone equates.
Distance between described the first microphone and the second microphone is 5mm.
The present invention equidistantly arranges two microphones in the acoustic absorbant dead ahead that needs are measured, the sound wave that loudspeaker sends obtains the acoustic pressure at two microphone places behind acoustic absorbant two secondary reflections, the a series of computing of acoustic pressure process at two microphone places obtains the reflection coefficient of acoustic absorbant, obtains the acoustical absorption coefficient of acoustic absorbant through Computer Processing.The present invention compares with prior art, and its effect is actively with obvious.It has overcome the shortcoming that foregoing traditional standing-wave-tube method and Reverberation room method are measured the acoustic absorbant acoustical absorption coefficient, obtained a kind of simply, measuring method efficiently.
Description of drawings
Fig. 1 is measurement acoustical absorption coefficient schematic diagram of the present invention.
Fig. 2 is that acoustic absorbant surface reflectance of the present invention is measured and the FB(flow block) of calculating.
Embodiment
A kind of method of time delay measurement acoustical absorption coefficient is at first arranged the first microphone and second microphone in the acoustic absorbant dead ahead that needs are measured, respectively the reflecting acoustic pressure P at two places, both sides
1And P
2, calculate according to following step afterwards:
(1) Laplace transformation at calculating the first microphone and second microphone place obtains P
1(S) and P
2(S);
(2) Laplace transformation of the reflection coefficient on calculating acoustic absorbant surface
(3) define x(t) and y(t);
(4) with x(t) and y(t) carry out Laplace transformation and obtain X(s) and Y(s);
(5) will
Carry out Laplace and change the reflection R that obtains acoustic absorbant;
(6) acoustical absorption coefficient of calculating acoustic absorbant
Distance between distance, second microphone and the acoustic absorbant between described the first microphone and the second microphone equates that its equidistant effect is better, and measurement result is better.Distance between described the first microphone and the second microphone is 5mm.The shape length of acoustic absorbant sample is 800mm, and width is 800mm.
Pi, Pr represent incident acoustic wave acoustic pressure in the sound field and the acoustic pressure of reflective sound wave,
It is the time of acoustical impedance.
By accompanying drawing as can be known, the incident sound pressure at the first microphone place is P(1), second microphone place incident sound pressure is P(2), its Laplace transformation is respectively:
The Laplace transformation of the reflection coefficient on acoustic absorbant surface
Can be expressed as:
Definition
With
For:
(4)
With formula (4), in (5)
With
Carry out Laplace transformation, obtain:
(7)
With formula (1), (2) substitution formula (6):
With formula (1), (2) substitution formula (7):
By formula (8), (9), (3) obtain:
Formula (10) is carried out obtaining after the Laplace inverse transformation reflection coefficient on acoustic absorbant surface
:
(11)
Obtain the reflection coefficient on acoustic absorbant surface
After, just can obtain the acoustical absorption coefficient of acoustic absorbant
:
(12)。
Claims (3)
1. the method for a time delay measurement acoustical absorption coefficient is characterized in that: at first arrange the first microphone and second microphone in the acoustic absorbant dead ahead that needs are measured, respectively the reflecting acoustic pressure P at two places, both sides
1And P
2, calculate according to following step afterwards:
(1) Laplace transformation at calculating the first microphone and second microphone place obtains P
1(S) and P
2(S);
(2) Laplace transformation of the reflection coefficient on calculating acoustic absorbant surface
(3) define x(t) and y(t);
(4) with x(t) and y(t) carry out Laplace transformation and obtain X(s) and Y(s);
(5) will
Carry out Laplace and change the reflection R that obtains acoustic absorbant;
(6) acoustical absorption coefficient of calculating acoustic absorbant
2. the method for time delay measurement acoustical absorption coefficient according to claim 1 is characterized in that: the distance between distance, second microphone and the acoustic absorbant between described the first microphone and the second microphone equates.
3. the method for time delay measurement acoustical absorption coefficient according to claim 2, it is characterized in that: the distance between described the first microphone and the second microphone is 5mm.
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| CN2012104064342A CN102914591A (en) | 2012-10-23 | 2012-10-23 | Method for measuring sound absorption coefficient by time delay |
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| CN2012104064342A CN102914591A (en) | 2012-10-23 | 2012-10-23 | Method for measuring sound absorption coefficient by time delay |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103675104A (en) * | 2013-11-26 | 2014-03-26 | 同济大学 | Method and device for measuring random incidence sound-absorbing coefficient/sound-absorbing quantity of material |
| CN103728378A (en) * | 2013-12-28 | 2014-04-16 | 中原工学院 | Method for measuring sound absorption coefficient by virtue of cepstrum |
| CN112782283A (en) * | 2019-11-07 | 2021-05-11 | 北京小米移动软件有限公司 | Sound absorption capacity measuring method and device |
Citations (3)
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|---|---|---|---|---|
| SU1265488A1 (en) * | 1985-07-17 | 1986-10-23 | Белорусский институт механизации сельского хозяйства | Device for measuring mean sound absorption coefficient of closed volume |
| CN101696955A (en) * | 2009-10-16 | 2010-04-21 | 西安交通大学 | Device for testing sound absorption performance of porous metal material under variable parameter temperature field |
| JP2012052987A (en) * | 2010-09-03 | 2012-03-15 | Takenaka Komuten Co Ltd | Sound adsorption coefficient measuring device, sound characteristics measuring device, method and program |
-
2012
- 2012-10-23 CN CN2012104064342A patent/CN102914591A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU1265488A1 (en) * | 1985-07-17 | 1986-10-23 | Белорусский институт механизации сельского хозяйства | Device for measuring mean sound absorption coefficient of closed volume |
| CN101696955A (en) * | 2009-10-16 | 2010-04-21 | 西安交通大学 | Device for testing sound absorption performance of porous metal material under variable parameter temperature field |
| JP2012052987A (en) * | 2010-09-03 | 2012-03-15 | Takenaka Komuten Co Ltd | Sound adsorption coefficient measuring device, sound characteristics measuring device, method and program |
Non-Patent Citations (1)
| Title |
|---|
| 朱从云: "主动吸声降噪理论与方法研究", 《中国博士学位论文全文数据库》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103675104A (en) * | 2013-11-26 | 2014-03-26 | 同济大学 | Method and device for measuring random incidence sound-absorbing coefficient/sound-absorbing quantity of material |
| CN103728378A (en) * | 2013-12-28 | 2014-04-16 | 中原工学院 | Method for measuring sound absorption coefficient by virtue of cepstrum |
| CN112782283A (en) * | 2019-11-07 | 2021-05-11 | 北京小米移动软件有限公司 | Sound absorption capacity measuring method and device |
| CN112782283B (en) * | 2019-11-07 | 2023-05-30 | 北京小米移动软件有限公司 | Suction capacity measuring method and device |
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Application publication date: 20130206 |