Research On Sound Power Measurement Based On Scanning Sound Intensity Technology

As an important acoustic parameter,sound power can provide a reliable basis for the noise estimation,used to locate the noise source and evaluate the energy of the noise.Accurate measurement of sound power is importan t for analyzing noise and developing noise reduction solutions.According to the measurement principle,the traditional measurement methods of the sound power are mainly divided into two kinds: the sound pressure method and the sound intensity method.The former mainly includes calculating the sound power by measuring the sound pressure.As the sound pressure is a scalar,the measurement result can only reflect the noise level of the measurement point,and it is impossible to judge the position of the noise source,the propagation form and the propagation direction.Thus it is difficult to obtain reliable analysis results.In addition,the current use of the sound pressure method needs strict requirements for the measurement environment,and it is hard to perform on-site measurements and high-precision measurements in the harsh environment.Through the sound intensity method,the sound power is obtained by measuring and then calculating the sound intensity.Sound intensity is a vector involving the concept of sound field,which can not only reflect the strength of noises,but also the propagation of noise energy from the sound source.Moreover,when the sound intensity method is used to measure the sound power,the requirements for the measurement environment are low and the measurement can be directly performed on site.The traditional sound intensity method for measuring sound power is limited by the disadvantages of hardware conditions.For example,a dual microphone probe is usually used as the sound intensity probe and the measurement accuracy of the dual microphone has a great influence on the result of the sound power measurement;measurement instruments are expensive;the accuracy is affected by manual operation,etc.These make the development of the method slow.In view of the importance of the sound power measurement in the noise field and the many problems existing in the measurement of sound power by the scanning sound intensity method,using a sound intensity measuring instrument,the sound power measurement technology based on scanning sound intensity method is studied and the error improvement method is proposed.The thesis is divided into five parts.The first one is the introduction of the research status and development trend of the domestic and abroad sound power measurement technologies.The superiority of the sound intensity method in measuring sound power among those sound power measurement methods is clarified.The second one is the introduction of the basic parameters of the noise measurement,including sound pressure,sound pressure level,sound intensity,sound intensity level,sound power and sound power level and the relevant principles and calculating methods.The basic principles and main methods of measuring sound power are given,especially the scanning sound intensity method.Two parameters of data spectrum analysis,1/3 octave and A weighting,are given,and the digital realization process is introduced.The third one is the introduction to the hardware composition of a sound intensity measuring instrument based on DSP+MCU dual-core designed for acoustic power measurement,mainly including data acquisition,data processing,human-computer interaction and power supply modules.The fourth one is the introduction to the processing and transmission process of sound power measurement data from the aspect of software design.The last one is the proposal of an improved method aimed at the errors in the process of processing the data in each part during the analysis of the measured sound power.