In Situ Measurement System Of The Sound Absorption Coefficient

Application of sound absorbing material is a very important kind of means to deal with the noise,sound absorption coefficient whitch is a parameter to measure the characterization of the sound material is now in attention of people.In this paper, we summarized the basic principle of the methods that we can use to measure the sound absorption coefficient and list the advantages and disadvantages of these method. Then on the principle of the two microphone method,we use single frequency signal that can be changed instead of white noise as the sound source to measure the sound absorption coefficient.Compared to the white noise signal source we use in the traditional way, the acoustic power of single frequency signal source is focus on one frequency point, so it is easy for us to deal with the influence of the broad-spectrum noise,it is helpful to realize the in situ measurement of sound absorption coefficient.This paper takes AT89c51 as the chip to control the working state of the other chips,and use tlv320aic23 b to transform the acoustic signal whitch is analog signal to digital signal,then tms320vc5402 can be the part that deal with the digital signal.On the basis that we talk above,we build the circuit for measuring the sound absorption coefficient that use the principle of two microphone method, and realize the reception of data that come from two way at the same time.In this paper I wrote the drivers for the chips that we used, and complete the program of the FFT and the formula.This paper gives some part of the source program and the flow chart, at the same time the program has been test by running in the hardware circuit.Finally,we verify the way that the difference of the phase and the ratio of the amplitude about the signal which we get from the two microphone influence the outcome of the system.At the same time, I complete the experiment recognising the frequency of the signal at a very short time.