Air-borne acoustic surface waves generated over a periodic rough surface

A surface composed of regularly-spaced rectangular strips is known to produce airborne acoustic surface waves that travel slower than the speed of sound and attenuate in the propagation direction with the square root of distance. Further laboratory measurements of propagation over a regular array are reported which seem to indicate the possibility of more than one surface wave. A code based on the Boundary Element Method has been extended to the time domain. It has been used to compare the data and to explore the surface wave effects. Varying the spacing, thickness and height of the strips is shown to affect the magnitude and frequency content of the air-borne surface waves generated by the periodic strip surface.