The Research On Sound Power Measurement System Based On LabVIEW

Sound power is an objective quantity reflecting the radiated noise energy of the machine,and has become an important indicator of mechanical product quality.Its accurate measurement could help people understand the characteristics of noise sources,study the causes of noise,find and develop reasonable noise reduction measures.Aiming at the shortcomings of the traditional sound power measurement instruments mostly regarding the hardware as the core,such as high complexity,high price level,and less flexibility,and considering the current development trend of instrument virtualization,this thesis uses microphone,signal conditioning circuit,and DAQ(Data Acquisition Card)as the hardware platform,and combines the technology of computer,virtual instrument,and Access database to set up the sound power measurement system based on LabVIEW.In this thesis,the approximate calculation error of the average-time-averaged sound pressure level is discussed firstly.The maximum error calculation formula is deduced,and the approximate calculation condition stipulated in the national standard GB/T 1094-10-2003 is verified.It is pointed out that the standard has the limitation to the application scope of the approximate method.Moreover,the factors that affect the approximate calculation error are re-discussed.By modifying the case where the fluctuation range exceeds 5 dB,the application range of the approximate method is extended.Secondly,the frequency weighting is studied.The design of the frequency weighting filter is deduced,and LabVIEW implementation program is given and verified.Then,the octave analysis algorithm are introduced and the multi-sampling rate digital filter bank algorithm based on LabVIEW is emphasized.Meanwhile,the half-band filter and octave band-pass filters are designed,and the frequency band and times that need to be sampled at different sampling points are determined by the multi-sampling rate digital filter bank algorithm.Finally,through the analysis of the system requirements,the overall design of the system is provided.In addition,the software design of each function module,the reliability and optimization design are described in detail.The sound power measurement system designed in this thesis could realize the parallel processing and analysis of the multi-channel signal,and obtain the frequency weighting and octave band sound power level of the noise source.The measurement of sound power level conforms to ISO 3744-2010 requirements for the reflective surface engineering method.When the tolerance is less than 1dB,the scope of approximate calculation application conditions of the average-time-averaged sound pressure level could be extended from 5dB to lOdB by error correction.Simulation results show that the performance of the frequency weighting filters and the multi-rate octave filters meet the attenuation requirements of the class 1 filters specified by IEC 61672-1-2002 and GB/T 3241-2010,respectively.