GTM-Grup de recerca en Tecnologies Mèdia, La Salle, Universitat Ramon Llull, C/Quatre Camins 2, 08022 Barcelona, Catalonia, Spain.
J Acoust Soc Am. 2013 Sep;134(3):1899-907. doi: 10.1121/1.4817905.
Parametric loudspeakers are often used in beam forming applications where a high directivity is required. Withal, in this paper it is proposed to use such devices to build an omnidirectional source of sound. An initial prototype, the omnidirectional parametric loudspeaker (OPL), consisting of a sphere with hundreds of ultrasonic transducers placed on it has been constructed. The OPL emits audible sound thanks to the parametric acoustic array phenomenon, and the close proximity and the large number of transducers results in the generation of a highly omnidirectional sound field. Comparisons with conventional dodecahedron loudspeakers have been made in terms of directivity, frequency response, and in applications such as the generation of diffuse acoustic fields in reverberant chambers. The OPL prototype has performed better than the conventional loudspeaker especially for frequencies higher than 500 Hz, its main drawback being the difficulty to generate intense pressure levels at low frequencies.
参数扬声器常用于需要高指向性的波束形成应用中。然而，本文提出使用这种设备来构建全向声源。已经构建了一个初始原型，即全向参数扬声器（OPL），它由一个球体组成，球体上放置了数百个超声波换能器。OPL 发出可听见的声音是由于参数声阵列现象，并且由于近距离和大量的换能器，产生了高度全向的声场。在指向性、频率响应以及在混响室中产生漫射声场等应用方面，与传统的十二面体扬声器进行了比较。OPL 原型的表现优于传统扬声器，特别是在高于 500Hz 的频率下，其主要缺点是在低频时难以产生强烈的声压级。
