Design Of Multifunctional Sound Level Meter Based On TMS320VC5502

To adapt to the great changes of the sound level meters in application scope and using function and meet the increasingly growing needs of the users, this thesis designs a multi-functional sound level meter with octave analysis and calculation of the commonly used noise assessments which include equivalent sound pressure level, sound exposure level, sound statistical level and noise because of the characteristics of the traditional sound level meters with single function, little noise rating of simultaneous measurement and being not sufficient and accurate in representational noise.First of all, this paper does researches and analyzes the main functions of the sound level meters including frequency-weighting, octave analysis and time-weighting. To reduce the errors of frequency-weighting in sound level meters based on bilinear transformation, an design method of frequency-weighting in sound-level meters based on particle swarm optimization(PSO) algorithm is introduced. By using PSO method to do search optimization on the IIR filter coefficient of the frequency weighting and the swarm intelligence of the cooperation and competition from the group, it can achieve the optimization design of the frequency weighting. By using the filter bank to do octave analysis, this thesis has introduced the design process of the octave filter bank in MATLAB, the octave analysis process based on down sampling and the digital design method of the time-weighting.Then, fully considering the requirements of the functions and applications of the sound level meters in the market, according to the current situation and development tendency home and abroad, this thesis has designed a kind of hardware solution to sound level meter based on the method of ACD+DSP+ARM. PCM1804, which is a 24-bit delta-sigma stereo A/D converter with fully differential analog voltage input produced by TI company is used as the A/D converting unit.TMS320VC5502, which is high performance and is a low power digital signal processing chip also produced by the TI company, is used as the hardware execution unit of the core algorithm in the sound level meters which improves the performance of the sound level meter in real-time. STM32F407 is applied in management unit to provide sufficient hardware resources in optimization user interface and functional design of the sound level meters.Finally, as a kind of software design for multi-function, the sound level meter is able to calculate the energy equivalent sound pressure level, statistical sound pressure level, noise exposure, noise dose and other commonly used noise assessment, even frequency analysis in one-third octave bands or in octave bands. Auto repeat measurement is designed for noise sensitive areas and 24 hours monitoring is designed for the serious noise pollution areas, both of which can store measurement results and the data can be uploaded to the PC for later analysis or management.The test result indicates that this kind of sound level meter meets the standard of class 1 instruments and the errors of each measurement are less than 0.1d B. The frequency weighting and linear errors meet the standards of GB/T 3785.1 2010 requirement for grade 1 sound level meter, octave filter errors meet the standards of GB/T 3241-2010 to the requirement of grade 1 filter.