Research Of Sound Intensity Measurement And Analysis System Based On DSP

Sound intensity technology is an important measurement technology in the field of acoustics.It is widely used in sound power measurement,mechanical fault diagnosis,quality control,sound source location,sound intensity line measurement,environmental noise monitoring and analysis.Especially,it has unique advantages in sound power measurement and main noise source identification.In view of the wide demand and application of sound intensity measurement in acoustic field,the sound intensity measurement algorithm is researched,a real-time sound intensity measurement and analysis system based on DSP is designed in this work,and the measurement error of the system is analyzed in detail,on this basis,the effective method to reduce the error was proposed.The thesis consists of five parts.Firstly,the research status and development trend of sound intensity measurement technology at home and abroad are reviewed,and the research significance of sound intensity measurement and analysis system based on DSP is pointed out.Secondly,the current sound intensity measurement method is introduced,and the method of cross power spectral sound intensity measurement based on pairs of microphones is expounded.At the same time,the digital implementation process of the sound pressure level,sound intensity level,1/3 octave and A weighting is given.Thirdly,the hardware system based on ADC&DSP&MCU is built.The system consists of four functional modules:data acquisition unit,data processing unit,management unit and power supply unit,the detailed circuit design is given.Fourthly,the software design of the data processing unit is given.The method of analyzing the sound intensity spectrum in the frequency domain based on multi-sampling rate is introduced in detail.The attenuation characteristics of the filter are verified by simulation experiments.Fifthly,the error of the system is analyzed,and the finite difference error,phase mismatch error and noise floor interference are analyzed in detail.The sound intensity calculation method based on geometric mean sound pressure is proposed to reduce the finite difference error and phase mismatch error,a noise cancellation method based on power spectrum correction is proposed to reduce the noise floor interference.The sound intensity measurement and analysis system designed in this thesis has the following measuring functions:real-time measurement of sound pressure level and sound intensity level,providing 1/3 octave sound intensity spectrum analysis and A weighting results.Test results show that the frequency response of sound pressure and sound intensity satisfies the requirements of 1st class sound intensity measurement system defined in national standard GB/T 17561-1998.The 1/3 octave analysis performance meet the verification requirements of 1st class sound intensity measurement system specified in national metrological verification regulation JJG 992-2004.The characteristics of A weighting in line with the provisions of JJG 992-2004.