Influence of White Noise in the Measurement of Acoustic Impedance of Some Industrial Insulating Materials.

Abstract

This study presents the influence of White Noise in the Measurement of Acoustic Impedance and Absorption Coefficients of some Industrial Insulating Materials using white noise generator instead of one-third of octave or sine wave and impedance tube with single moveable microphone. The standing wave method is used to measure the acoustic properties (absorption coefficient and acoustic impedance) of sound absorbing materials. A burst of white noise and a signal processing technique was used. The algorithm is based on the equation of simple harmonic motion, however,distance was used as a variable, instead of time. This measurement allows frequency resolutions as low as 5 Hz in a reasonably short amount of time. Although the frequency resolution of 5 Hz and distance of 1cm may not have affected the sampling rate for each time of measurement, but these features of the frequency resolution and distances used does affect the results by the responses of the signals that is produced.