Sound radiation from convex and concave domes in an infinite baffle

Abstract

The sound radiation from convex and concave rigid diaphragms represented by portions of a spherical surface was investigated for the purpose of modeling a direct radiator loudspeaker. Pressure responses, radiation impedances, directivity patterns, and some other characteristics were obtained and compared with those of a circular flat diaphragm of the same radius. While the on axis pressure response of the rigid flat piston remains constant, the response of the convex dome decreases for about ka?1.0 as the height of the dome increases. The concave dome has a wide smooth peak around ka=1.5 and several peaks and dips for larger values of ka. The radiation resistance of the convex dome increases by the rate of 12 dB/oct or less up to ka=2.0 and remains constant in the higher frequency regions. On the other hand, the radiation resistance of the concave dome has its largest peak at the frequency corresponding to the peak of sound pressure response. The directivity patterns of either the convex or concave dome do not have minima with zero sound pressure and their radiation patterns are generally wider than those of the circular plate. All these results are well explained by the energy flow and pressure distribution near the radiator.