The Influence of Diffuse-Field Equalization on the Perception of Spatial Aliasing Introduced by Spherical Microphone Arrays

When a sound field is sampled by a finite number of microphones, the upper-frequency range of the recorded content is affected by spatial aliasing. The frequency beyond which aliasing-induced artifacts occur is related to the distance between a microphone and its nearest neighbors. In this study, ambisonics signals of order N = 7 were encoded from simulated recordings made by virtual spherical microphone arrays of varying characteristics (radius, sampling scheme, and sampling grid order). A diffuse-field equalization, the role of which is to lessen the aliasing-induced spectral coloration, was also considered in the tested conditions. These aliased stimuli were then compared with unaliased stimuli of order N = 7. Results showed that the diffuse-field equalization had a great impact on the perceived differences. A perceptual threshold was calculated in order to determine whether aliasing artifacts are likely to be audible based on the amount of aliasing-induced encoding error.