Coupling of sound spaces by plane surface harmonics and its application to sound source characterization

Abstract

The coupling of two acoustical spaces via an interface surface can be done using the concept of surface impedance. The latter can be constructed by expanding the sound field across the interface into a truncated series of suitably chosen elementary surface functions. The prediction of air-borne sound emitted by a sound source into an arbitrary receiving space can then be done by defining a virtual interface surface around the source and by characterizing the source as well as the receiving space across it. With respect to this surface the source can be characterized by its blocked sound pressure and its surface impedance; in such a case the receiver is characterized by its own surface impedance. Each of these three quantities is expressed by a number of continuous spatial functions. While the interface surface can have any geometry the paper focuses on interfaces made of one or several plane rectangular surfaces. The approach is demonstrated by the cases of a multi-point source and of a vibrating box source.