Development of a Time-Efficient Approach to Measure the Acoustic Impedance of Industrial Insulating Materials.

Abstract

This study presents a development on a time efficient approach to measure the Acoustic Impedance of Industrial Insulating materials using an impedance tube with single moveable microphone and a white noise generator. The standing wave method is used to measure the acoustic properties (absorption coefficient and acoustic impedance) of sound absorbing materials. In order to use a burst of white noise instead of individual stationary sine waves, a signal processing technique was developed. The algorithm is based on the equation of simple harmonic motion, but uses distance as a variable, instead of time. This innovative method allows measuring at frequency resolutions as low as 5 Hz in a reasonably short amount of time. This is an advantage, as the classical standing wave method uses frequency resolutions of one-third of octaves for measurements, as otherwise time would be prohibitive. Experimental results are validated with those measured with the sine wave generator using one-third of octave frequencies by comparing their behaviours.