Method for measuring sound absorption coefficient by time delay

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 [0001] The invention belongs to the field of noise, and in particular relates to a method for measuring the sound absorption coefficient of a sound-absorbing material. Background technique [0002] Sound absorption and noise reduction is the use of sound-absorbing materials or sound-absorbing structures to reduce noise. The sound absorption mechanism of sound-absorbing materials is: when a sound wave is incident on the sound-absorbing material, due to the damping effect of the sound-absorbing material, part of the sound wave is absorbed and consumed by the sound-absorbing material, and part of the sound wave is reflected back. Therefore, the sound absorption coefficient is defined as the ratio of the sound energy absorbed by the sound-absorbing material to the sound energy of the incident sound wave. Traditional sound absorption coefficient measurement methods mainly include standing wave tube method and reverberation chamber method. The measurement princ...

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Problems solved by technology

However, there are some shortcomings in measuring the sound absorption coefficient of sound-absorbing materials with the standing wave tube method, mainly as follows: 1. Errors will be caused when the probe searches for the maximum and minimum values ​​of the sound pressure; 2. The sound absorption of the sound-absorbing material cannot be obtained immediately 3. The measurement of the sound absorption coefficient of loose materials such as sand is powerless; 4. The size of the sound-absorbing material sample must be precisely matched with the size of the standing wave tube, otherwise it will cause a large error

The principle of measuring the sound absorption coefficient of the sound-absorbing material by the reverberation chamber method is to obtain the sound absorption coefficient of the sound-absorbing material by measuring the reverberation time, but there are some shortcomings in measuring the sound absorption coefficient of the sound-absorbing material by the reverberation chamber method, mainly There are: 1. The measured value of the sound absorption coefficient of the same material in each reverberation chamber is sometimes very different, so that the measurement results are not comparable; 2. The size of the sound absorption coefficient varies with the change of the material area and its indoor position. change, and the sound absorption coefficient of these materials in the middle and high frequency bands may be greater than 1

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