Design Of Noise Measurement And Analysis System Based On Sound Card

Noise measurement plays an important role in controlling or using noise. Measurement of noise can be used in various fields.Hardware measurement instruments are used in traditional way, but the hardware instruments had a long design cycle and a single function. It is difficult to write communication protocol for computer. In order to reduce the difficulty of instrument design and simplify the measuring process, in this thesis a measurement noise analysis system based on sound card was designed through multiple application technology such as sound card, virtual instrument, ActiveX and digital signal processing technology etc.The thesis introduced FFT and digital filter method which were the calculation methods of octave and third octave. For the sake of improving the Signal-to-noise ration, second wavelet transform filter was put forward on the basis of ameliorating Mallat algorithm in wavelet transform.On that foundation, the Mutirate digital filters to calculate octave and 1/3 octave along with second wavelet transform filter were designed by using LabVIEW and testified by simulation.Based on the realization of Multirate digital filters to calculate octave and 1/3 octave and second wavelet transform filter, the noise measurement and analysis system was built by LabVIEW and sound card. The system can calculate the evaluation of the amount of noise, including frequency weight, time weight, peak pressure, Leq, LDN, sound exposure level, and realize the measurement data display, storage and report generation which is convenient for future reference. The system was applied in fault analysis of automobile engine to test the practicability.The noise measurement and analysis system based on sound card can effectively improve the Signal-to-noise ration and the measurement of noise meet the equirement of JJB1034-2005 acoustic Metrological Terms and their definitions and other national measurement standards. Compared with the multi rate sampling FFT method?the results of octave and 1/3 octave can not only be in accordance with the provisions of GBT 3241-2010 octave filter but also have higher resolution of low frequency noise signal. Automobile engine fault diagnosis experiments show that, the noise measurement and analysis system can accurately judge whether the fault occurs.