Perceptual evaluation of approaches for binaural reproduction of non-spherical microphone array signals

Abstract

Microphone arrays consisting of sensors mounted on the surface of a rigid, spherical scatterer are popular tools for the capture and binaural reproduction of spatial sound scenes. However, microphone arrays with a perfectly spherical body and uniformly distributed microphones are often impractical for the consumer sector, in which microphone arrays are generally mounted on mobile and wearable devices of arbitrary geometries. Therefore, the binaural reproduction of sound fields captured with arbitrarily shaped microphone arrays has become an important field of research. In this work, we present a comparison of methods for the binaural reproduction of sound fields captured with non-spherical microphone arrays. First, we evaluated equatorial microphone arrays (EMAs), where the microphones are distributed on an equatorial contour of a rigid, spherical 1. Second, we evaluated a microphone array with six microphones mounted on a pair of glasses. Using these two arrays, we conducted two listening experiments comparing four rendering methods based on acoustic scenes captured in different rooms2. The evaluation includes a microphone-based stereo approach (sAB stereo), a beamforming-based stereo approach (sXY stereo), beamforming-based binaural reproduction (BFBR), and BFBR with binaural signal matching (BSM). Additionally, the perceptual evaluation included binaural Ambisonics renderings, which were based on measurements with spherical microphone arrays. In the EMA experiment we included a fourth-order Ambisonics rendering, while in the glasses array experiment we included a second-order Ambisonics rendering. In both listening experiments in which participants compared all approaches with a dummy head recording we applied non-head-tracked binaural synthesis, with sound sources only in the horizontal plane. The perceived differences were rated separately for the attributes timbre and spaciousness. Results suggest that most approaches perform similarly to the Ambisonics rendering. Overall, BSM, and microphone-based stereo were rated the best for EMAs, and BFBR and microphone-based stereo for the glasses array.

Spatial Subtraction of Reflections from Room Impulse Responses Measured with a Spherical Microphone Array

“…Depending on the specific microphone array and sound field assumptions, three non-parametric binaural rendering methods are considered state-of-the-art: magnitude-least-squares-optimal rendering (magLS) [5], [35], [36], beamforming-based binaural reproduction (BFBR) [37], [38], and binaural signal matching (BSM) [39], [40]. The most recent iterations of these methods often combine ideas of the approaches, e.g., in [41] BSM was implemented with magnitude optimization at high frequencies and [39] combines BFBR and BSM. Differences between specific implementations of the methods depending on assumptions on the microphone array and the sound field are thus often greater than general differences between the methods.…”

Six-Degrees-of-Freedom Binaural Reproduction of Head-Worn Microphone Array Capture

“…Examples of studies involving the direct binaural reproduction of head-worn arrays in the eyeglasses form-factor include the use of LS [37] or MagLS [38] solutions, which aim to fit the array directivities directly to the target binaural directivities. A general parametric spatial enhancement solution was also explored recently in [39], which demonstrated improved spatial accuracy over alternative signalindependent algorithms.…”