Sound propagation over periodically grooved convex surfaces

• Propagation over grooved, convex surfaces is measured and modelled numerically. • Simulated and measured pulses show tails attributable to organ pipe resonances in the grooves. • Excess attenuation peaks correspond to higher pressure near the surface. • indicating a surface wave. • A high finite impedance on the grooves and curved surface is predicted to eliminate the surface wave. A numerical Boundary Element Method is used to investigate the propagation of cylindrical sound waves over rigid, grooved, convex surfaces at audio-frequencies. Laboratory measurements with broadband excitation and corresponding predictions reveal peaks in excess attenuation spectra. With short pulse excitation, measurements and predictions show delayed signals or “tails” following the main pulse arrivals. The spectral content of these tails corresponds to the peaks on the excess attenuation spectra and can be attributed to organ pipe (or quarter wavelength) resonance in the grooves. Predictions of the two-dimensional distribution of sound at the frequencies of these peaks show that the pressure field is restricted to a thin layer above the curved grooved surface, indicative of a surface wave which is eliminated by a very high finite impedance.