Analysis of absorption in situ with a spherical microphone array

Measured values of acoustic absorption often vary between the laboratory and the field due to deficiencies in standard measurement methods. This paper introduces a new method of measuring acoustic absorption in the field using a spherical microphone array. Plane-wave decomposition is used to separate direct energy from reflected energy when the array is placed adjacent to the absorptive sample. Additional signal processing techniques including the Dolph-Chebyshev beampattern and Delay-and-Sum processing are introduced and used to improve the method. The method is verified by simulation for normal and oblique incidence and by experiment for normal incidence.