The Research On Key Technology Of Sound Power Measurement And Analysis Based On LabVIEW

The traditional sound power instrument has the following defects: high price, single function, complicated and time-consuming operation, and inefficient measurement; limited memory causes that the users have to delete history data when the memory is full, which makes the users cannot manage the measured data effectively; taking advantage of Liquid Crystal Display(LCD) to show the measured acoustic parameters, because of the screen size is limited, the LCD could only show finite parameters and cannot display data by personalized chart.Aiming at the shortcomings of traditional sound power instrument, and combining with the developing trend of the instrument at present, this thesis utilizes microphone, signal processing circuit, Data Acquisition(DAQ) Card and the sound power measurement and analysis software to set up the sound power measurement and analysis system. The system makes full use of the computer system’s powerful data processing ability. With the basic hardware support, sound power measurement and analysis software can realize various functions of the traditional sound power measuring instruments, which is a software developed on Lab VIEW software platform, including the functions of data acquisition, data processing and analysis, data management and browsing, report output, etc.This thesis consists of five parts: Chapter 1 is an introduction, which reviews the present research status and development trend of sound power measurement technology both at home and abroad, points out the significance of sound power measurement and analysis system based on Lab VIEW. Chapter 2 specifies a method for determining the sound power level of a noise source in situ in a reverberant environment, and the calculation process of octave-band sound power level with a single or multiple calibrated reference sound sources. Chapter 3 has a further study of the critical parameter of the comparison method in situ, which is a calculation method of the sound power level with frequency A-weighting applied using the octave-band levels based on multi-sampling rate. Meanwhile, the design of the anti-alias FIR filter and IIR octave band-pass filter is described in detail. Chaper 4 designs the octave band pass filter and anti-aliasing filter based on Lab VIEW, verifies the filtering characteristics of the designed filters by simulation experiments, and compares the analytical precision and computational complexity of the two methods of time-domain octave analysis. Chapter 5 introduces the structure of sound power measurement and analysis system, tells the working principle of the system, provides the overall design and functional module design of the sound power measurement and analysis system through analyzing the requirements of the system, and detailedly illustrates the design and realization mode of the data acquisition module, data processing and analysis module, data browsing module, report output module, etc.The sound power measurement and analysis system designed in this thesis has the following measuring functions at present: analyzing the octave spectrum of multi-channel acoustic signals in parallel, and measuring the sound power level of non-moving sound source. The practical operation results shows that the system has the following advantages: friendly human-computer interface, simple operation, less manual intervention, high automation, stable and reliable running, etc. The frequency attenuation characteristics of the octave filters which are designed in time domain octave analysis algorithm based on multi-rate meet the requirements for level 0 filter that is ruled by GB/T 3241-2010. The measurement of sound power level of mechanical equipment conforms to GB/T 16538-2008.