Research Of Sound Intensity Measurement Based On DSP

Sound intensity measurement is an important measurement technology in the field of acoustics.It is widely used in sound power measurement,sound source direction determination,environmental noise monitoring and machine fault diagnosis and so on.At present,domestic sound intensity measurement system generally adopts the technical scheme of "sound intensity probe + signal conditioning circuit + data acquisition card + computer",which is expensive and not easy to carry,which seriously restricts the further application of sound intensity measurement technology in the field of acoustic measurement.In order to solve the above problems,this paper in HengYang HengYi Electric Company commissioned the development of the project "sound intensity measurement instrument research and development" support,carriy out the sound intensity measurement method research,on this basis,develop a portable sound intensity measurement instrument based on DSP.This paper mainly carries out the following four aspects of research work:(1)By comparing and analyzing the advantages and disadvantages of various sound intensity measurement methods,this paper mainly explains the principle of measuring the sound intensity by using the frequency domain p-p method and describes the digital realization process of this method.(2)Two implementation methods of the frequency weighting in the digital filter and the FFT are compared and analyzed,and their applicable applications are given.(3)According to the analysis of the existing octave analysis method-time domain bandpass filter bank algorithm and fixed sampling FFT algorithm,it is found that there are many defects such as large amount of calculation,poor real-time performance and large error in low frequency band,and it is difficult to meet the requirements of the measurement accuracy and real-time of the sound intensity measurement instrument to octave analysis.Therefore,this paper proposes an FFT octave analysis algorithm based on multiple sampling rate,improves the real-time performance of the system the measurement accuracy of low frequency band.(4)The hardware platform of "double microphone probe + signal conditioning circuit + PCM1804 + DSP(TMS320C6748)" is constructed,and the software design flow based on SYS/BIOS is given,the design of sound intensity measuring instrument is completed.Sound intensity measurement instrument has the functions of sound intensity level measurement,sound pressure level measurement,octave analysis and so on.By dividing the measurement tasks reasonably,the high precision real-time measurement analysis can be realized.The result of experiment show that the sound intensity level of A frequency weighting meets the requirements of the national metrology verification regulation JJG 992-2004 for the verification of first-level sound intensity meter,and the performance of multi-sampling rate FFT octave analysis meets the requirements of the national standard GB/T 3241-2010 for the first-level octave filter.