On the Local Plane Wave Methods for in Situ Measurement of Acoustic Absorption

In this paper we address a series of so-called local plane wave methods (LPW) to measure acoustic absorption. As opposed to other methods, these methods do not rely on assumptions of the global sound field, like e.g. a plane wave or diffuse field, but are based on a local plane wave assumption. Therefore, the LPW methods can be used for any given surface/absorbing material and any arbitrary sound field. The absorption coefficient can be calculated based on a measurement of the acoustic pressure in a number of points in the vicinity of the absorbing surface. The local plane wave methods are illustrated by some numerical and experimental examples.