Sound Source Directivity Estimation in Spherical Fourier Domain from Sparse Measurements

Real sound sources have unique directional properties unlike simple idealised sources such as monopoles. Measur-

ing the directivity patterns of sound sources typically involves measuring sound power using pressure microphones

on a spherical grid surrounding the source. This approach is not very practical and is costly due to hardware

requirements. This paper proposes a reduced-complexity source directivity measurement approach. The spherical

harmonic decomposition of the sound field at a small number of measurement points around the source is first

obtained. Both pressure and its higher-order spatial derivatives are then calculated to estimate source directivity that

best matches a fixed-order model. The proposed approach is validated to assess its utility using eight second-order

measurements around a loudspeaker. The estimated directivity functions closely matched the manufacturer data,

particularly at low and mid-frequency bands.