Design Of A Measurement System For Material Absorption Coefficient

The main acoustic properties of the material is sound absorption, so how to measure the sound absorption coefficient preciser and faster has an important significance about the design of acoustic material and noise measurement.The main method of the sound absorption coefficient measurement including standing wave ratio method, transfer function method, the reverberation chamber method. Through the summary and comparison to the above three methods, this paper given the difference, advantages and applicable conditions of the three kinds of measurement method. This paper also given specific dual-microphone transfer function measurement of the material absorption coefficient, solve the problem of mismatch and phase distortion of the channel between the microphone. The experimental results show that this system has a high measurement accuracy, can be realized the absorption coefficient measurement rapidly and accurately.In hardware design, according to national standard, the paper designed two sets of impedance tube for different frequency bands, determined the Parameters of impedance tube such as wall thickness, microphone position, microphone spacing, specimen tube, rod and sample holder etc.About the software, according to the two-microphone transfer function method and NI graphical editing language LabVIEW software, as well as the sound pressure signal from the power spectrum and cross-power spectrum, design a set of sound absorption coefficient measurement system to achieve the accurate measurement of the absorption coefficient of materials.Finally, between signal and wide broadband sound source condition, the paper discuss the test results of the measured absorption coefficient.