Spatial alignment of acoustic sources based on spherical harmonics radiation analysis

The radiation pattern of sound sources such as loudspeakers, musical instruments, the human voice and machines is of importance in a wide range of applications. Recently, radiation analysis has been studied by measuring the sound field around the source using spherical microphone arrays, and computing the spherical harmonics spectrum of the radiated sound field. However, the latter may change with the positioning of the source inside the measurement array, leading to a potential difficulty in determining the acoustic radiation pattern consistently. This paper presents the theoretical analysis of the spherical harmonics spectrum of spatially translated sources, and proposes several measures for the deviation of sources from their acoustic center. These measures can then be used for spatial alignment of sources, overcoming inconsistency due to misalignment.