Spatial perception of sound fields recorded by spherical microphone arrays with varying spatial resolution.

The area of sound field synthesis has significantly advanced in the past decade, facilitated by the development of high-quality sound-field capturing and re-synthesis systems. Spherical microphone arrays are among the most recently developed systems for sound field capturing, enabling processing and analysis of three-dimensional sound fields in the spherical harmonics domain. In spite of these developments, a clear relation between sound fields recorded by spherical microphone arrays and their perception with a re-synthesis system has not yet been established, although some relation to scalar measures of spatial perception was recently presented. This paper presents an experimental study of spatial sound perception with the use of a spherical microphone array for sound recording and headphone-based binaural sound synthesis. Sound field analysis and processing is performed in the spherical harmonics domain with the use of head-related transfer functions and simulated enclosed sound fields. The effect of several factors, such as spherical harmonics order, frequency bandwidth, and spatial sampling, are investigated by applying the repertory grid technique to the results of the experiment, forming a clearer relation between sound-field capture with a spherical microphone array and its perception using binaural synthesis regarding space, frequency, and additional artifacts. The experimental study clearly shows that a source will be perceived more spatially sharp and more externalized when represented by a binaural stimuli reconstructed with a higher spherical harmonics order. This effect is apparent from low spherical harmonics orders. Spatial aliasing, as a result of sound field capturing with a finite number of microphones, introduces unpleasant artifacts which increased with the degree of aliasing error.

Interaural cross correlation in a sound field represented by spherical harmonics.

Spatial impression is an important acoustic quality of concert halls. An accepted objective measure for spatial impression is the interaural cross-correlation (IACC) coefficient. Recently, spherical microphone arrays have been studied for room acoustics analysis and music recordings. This study presents a theoretical formulation for the computation of IACC using spherical-harmonics representations of the sound field, as measured by spherical microphone arrays, and spherical-harmonics representation of head-related transfer functions (HRTFs), taken from HRTF databases. As spherical microphone arrays typically use a finite number of microphones, they may not be able to capture the complete spatial information in a sound field. Therefore, the effect of limited spherical-harmonics order on the accuracy of IACC approximation using the proposed method is studied using simulated and measured data. The method presented in this paper can be further used to study the effect of limited spatial information on the spatial perception of sound fields.