A “composite” stepped plate for use in highly directional parametric array loudspeakers

Abstract

It has been shown that stepped plate radiators with appropriately designed steps can be used in highly directional parametric array (PA) loudspeakers [Hwang and Moon, 170th Meeting of the Acoustical Society of America, 138(3), 1801(2015)]. To improve the performance of the PA loudspeaker, a relatively thin plate with steps needs to be adopted for its higher power efficiency. However, the natural frequencies of the plate and the corresponding mode shapes depend on the mass of the steps. Hence, it can be difficult to design a stepped plate suitable for use in PA loudspeakers. In this paper, we propose a novel plate design, with steps composed of a stiff, lightweight, polymer material. The steps were fabricated with a thickness of 2.3 mm from a polymer material with an elastic modulus of 1 GPa, a Poisson ratio of 0.23, and a mass density of 540 kg/m3 on the plate with a thickness of 1 mm. Experiments and simulations were carried out to determine the acoustic characteristics of our fabricated “composite” stepped plate. [Work supported by NRF 2016R1E1A2A02945515).]