The Application Of Three-dimensional Sound Intensity Method In Measuring Sound Absorption Coefficient

Measuring the sound absorption coefficient of materials is an important part of architectural acoustics measurement.The traditional methods to measure the absorption coefficient include standing wave tube method and reverberation chamber method.In this paper,based on the vector characteristics of the measured three-dimensional sound intensity,a four-microphone sound intensity probe is used to calculate the corresponding sound absorption coefficient by measuring the amplitude of the sound intensity reflected by the tested specimen and the total reflector plate respectively.This method does not need to destroy the material and has low requirements for the measurement environment.It can not only measure the sound absorption coefficient of any Angle within the range of 0°?90° but also can measure the incident angle at the same time.The research is mainly carried out from the following four aspects: firstly,the theoretical research on the measurement of sound absorption coefficient by three-dimensional sound intensity method.Starting from the measurement of sound absorption coefficient of one dimension sound intensity with two probes,the research gradually explores the measurement system of three dimension sound intensity with four probes,and establishes a theoretical framework for the following experimental research.Secondly,Matlab is used to conduct numerical simulation of the theoretical system to preliminarily explore the accuracy of the measurement system.Additonally,the influence of frequency,incident Angle,material absorption coefficient and other factors on the accuracy of the whole measurement system is explored with the help of the computer's fast computing power so as to better determine the following experimental research direction.Thirdly.Labview is used to build a simple and easy to understand experimental operation software system,so that the surveyor can get the desired measurement results more conveniently.Lastly,the measurement system shall be verified in the laboratory so as to further explore the accuracy and effectiveness of the measurement system.Finally,the simulation results show that the measurement error of the sound absorption coefficient of the system is related to the measured frequency,the sound absorption coefficient of the measured material and the incident Angle.The directional error of the measurement system is related to the frequency and incident Angle of measurement.The experimental results show that the error range between the absorption coefficient and the simulation value of the measurement system is ± 0.02? ± 0.10 at the frequency of630Hz?4000Hz,the directional error range is 1° to 6°,and the directional error range from0° to 80° is 1° to 3.5°,which meet the requirements of measurement accuracy.So this measurement system has certain feasibility.