Acoustic emissions from convected wave packets

作者：Obrist Dominik^*

来源：Physics of Fluids, 2011, 23(2): 026101.

DOI：10.1063/1.3540693

Localized acoustic sources can often be modeled by wave packets. It has been recognized for a long time that the particular structure of these wave packet sources has a strong influence on the character of the acoustic emission to the far field. In the present work, we study the acoustic emission patterns with respect to the phase velocity, group velocity, size, and aspect ratio of the wave packet sources. To this end, the acoustic problem is formulated on the basis of Lighthill's acoustic analogy and then recast to the geometrical problem of conic sections. This leads to the notion of elliptic (subsonic), parabolic (sonic), and hyperbolic (supersonic) acoustic emission patterns. The resulting geometric theory for acoustic emissions from wave packets includes phenomena such as Mach waves, bi- and superdirectivity, Doppler shift, and silent directions.

• 出版日期2011-2