A STUDY OF BARRIER ATTENUATION BY USING ACOUSTIC IMPULSES

Acoustic impulses with a duration of about 2 ms have been used to measure the attenuation of full-sized barriers, including thin edges, wedges, and wide barriers. A technique involving two microphones was used which permits the direct comparison of the diffracted and undiffracted pulse waveforms. This allows the attenuation to be determined with an accuracy of better than 1 dB over the range 700 Hz-12 kHz from a single measurement set. The experimental results are compared with predictions from a variety of approximate and exact diffraction theories. As impulses involve both phase and magnitude information, they form a rigorous test of the theories. One advantage of the experimental technique is that it permits effects due to nonideal features, such as supporting struts, to be rapidly observed.