The Research On The Method Of Room Reverberation Analysis Based On Nearly Double Periodic M-sequences

Reverberation time is the most important part of room acoustics research and the most important reference of room sound quality evaluation. An effective, accurate and economical method of reverberation analysis is the premise and foundation of sou nd quality evaluation, acoustic testing of material, noise control and real time control of reverberation time by computer program.Reverberation measuring instrument are very expensive with a low degree of visualization. Reverberation measurement requires large amount of computation and storage. This thesis researched the algorithm of sound impulse response measurement and reverberation estimation for rapid analysis of reverberation, and designed a reverberation analysis system based on HY114 or HY114 B sound level meter, using Lab VIEW as the development platform. This system has realized the functions of the design of incentive sound source generator, the communication of hardware and software, calculating sound impulse response, 1/3 octave analysis and calculating reverberation time and other important parameters of room acoustics. It can also manage the measurement and analysis data, including graphical display, storage, classification, delete and output. This thesis is divided into five parts. First of al l, it expounded the domestic and international research status and development trend of reverberation measurement, and pointed out the significance of reverberation measurement and real time analysis system based on virtual instrument. Secondly, it researched the relevant theory of room reverberation, introduced the principle of noise measurement and reverberation measurement, focusing on the principle of reverberation time measurement by sound impulse response backward integration and deviation in reverberation measurement. Thirdly, it researched the method of sound impulse response measurement, focusing on the method of m-sequences, then proposed nearly double periodic m-sequences method based on the method of m-sequences, verified its feasibility by simul ation, compared the advantages and disadvantages of two measurement methods. It is demonstrated that nearly double periodic m-sequences method can achieve good effect in measurement of low order case, and less computation and storage than that in the m-sequences method. Fourthly, it researched reverberation estimation, focusing on the method of obtaining the attenuation curve of sound pressure level, and then introduced the method to estimate the reverberation time by the attenuation curve of sound pressure level. Finally, introduced the structure of the system, designed each functional modules of the software, expounded the concrete implementation of them on Lab VIEW, including display and user operation module, source control module, noise measurement modul e, data processing and analysis module, data management module and data output module.The design of reverberation analysis system in this thesis has a friendly interactive interface, simple operation, strong commonality. It is easy to implement function extension and modification and maintenance of late. It has a high degree of visualization,it is convenient for people to analyses reverberation. It can improve the penetration rate of reverberation measurement and analysis. It can measure reverberation time and other important parameters of room acoustics rapidly, and be used in reverberation estimation or real time reverberation monitoring to improve the interior sound quality.