Dissertation > Industrial Technology > General industrial technology > Acoustic engineering > Acoustic measurements

Research on the DSP Based Real-time Sound Intensity Measurement System by Use of the Two-microphone Cross Spectral Method

Author JinCheng
Tutor ChenZhangWei
School Zhejiang University
Course Mechanical and Electronic Engineering
Keywords Cross-spectrum sound intensity measurement Sound intensity error analysis Real - time signal analysis Spectrum estimation Octave analysis DSP
Type Master's thesis
Year 2007
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Relative to the a mature sound pressure measurement techniques, sound intensity measurement technique or a young acoustic measurement means. Sound intensity is defined as the process of wave propagation space per unit area on the transmission of sound power, it points to the direction of propagation of sound. Can be obtained for a sound source, as long as the envelope surface of the sound intensity vector for integration, surrounded acoustic power of the sound source, interference noise can be offset outside the measurement region can therefore be accurately in ordinary circumstances Determination of Sound Power. Using sound intensity direction information contained can easily identify the sound source and the acoustic energy distribution and dissemination. Sound intensity measurement technology has been in the determination of sound power, the main noise source identification, determination of the acoustic characteristics of the material has played a very important role. Therefore, the study of sound intensity measurement theory, and on this basis to develop a real-time sound intensity measurement and analysis system suitable for China has a very important significance. The subject a comprehensive comparison of the advantages and disadvantages of the existing sound intensity measurement technology to achieve a variety of ways, innovative use of the three parts of the Sound Intensity Probe DSP multi-channel signal analysis system and PC-based real-time sound intensity measurement system hardware architecture dual-microphone probe used to obtain two-way sound pressure signal, multi-channel DSP processing system for real-time sound digital signal processing, including FFT computation, the sound intensity octave spectrum calculation, the A-weighted sound power spectrum calculation; PC machine for data storage, display, and some of the subsequent processing. The hardware structure of the full advantage of the fast DSP computing capability and powerful PC graphics display capabilities, to achieve the most optimization purposes. Software algorithms on this subject prior to FFT calculation, the digital sound pressure of the two measurement channels, respectively, as the real part and the imaginary part of the composition as a plural, the plural first FFT calculation, and then separated from the calculation result obtained road sound pressure spectrum, using this method only through a spectrum transform calculation and simple addition and subtraction operations can also get dual microphone sound pressure of the digital spectrum, and greatly reduce the computation amount. Error compensation, subject geometric average sound pressure instead of the usual arithmetic average sound pressure dual-microphone method to calculate the sound field sound pressure level, so not only can effectively reduce the high frequency sound intensity measurement error, the error of the finite difference played a compensation effect, but also greatly reduces the amount of calculation in the calculation of the sound pressure spectrum. The experiment proved that the system met the design requirements in sound intensity measurement accuracy and real-time.

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