광대역 파라메트릭 어레이 음원을 위한 새로운 스텝 플레이트 트랜스듀서

Abstract

A parametric array is a nonlinear conversion phenomenon of a medium that can generate a high-directionality sound beam with a small sound radiation source than directly generated sound. The high-directionality sound generated in air can develop the personal sound spaces that send a voice or music to a particular person without the use of other devices, such as earphones, headphones, or wireless tools. Generally, the parametric array phenomenon does not spread widely because the sound pressure levels of the sound generated by a parametric array are extremely low. Because of this, the wideband frequency response of the sound generated by the parametric array should be considered for loudspeaker applications. In order to make a high directionality sound by a parametric array, both high-intensity, high-efficiency sound generation and a wideband frequency response sound from the radiation source must be achieved. Some of the available parametric array loudspeaker products have been analyzed, developed, and commercialized using an array-type sound source to generate a high-intensity, high-directionality sound beam. However, array-type transducers require uniform characteristics, such as resonance frequencies and sound pressure levels. The price of the fabrication of these array transducers is high. The stepped plate transducer, which consists of a Langevin transducer, a horn, and a radiating plate with steps, can generate the required high-intensity, high-directionality sound beam on the acoustic axis by using a transducer that is manufactured by the unit structure type. This study investigated the use of the stepped plate transducer to make a parametric array source that generates sound with high intensity, high-directionality, and a wide bandwidth. The stepped plate transducer has a larger radiation area than its driving components, which is called the Langevin transducer, for high acoustic radiation efficiency with high-intensity sound generation. The stepped plate transducer, which has two different resonance frequencies (f1 = 77.5 kHz, f2 = 87.4 kHz), was designed for a wide bandwidth, and the three different heights of the steps on the plate (ts1 = 2.28 mm, ts2 = 2.14 mm, ts3 = 2.02 mm) were designed for high-directionality sound beams. The fabricated stepped plate transducer demonstrated a 50 ± 3 dB sound pressure level at the difference frequency wave in the 4 kHz ~ 19 kHz frequency range (with equalization), and a 4.2 ~ 5.1° half-power beam width was shown for the high-directionality sound beam. The acoustic radiation efficiency of the transducer was 23% at its second resonance frequency (f2), and the results of the thin plate design confirmed that the radiation efficiency can be increased. This type of simple, unit structure-type transducer has high potential in sound privacy fields and carries low costs.