Evaluation of Spherical Wavelet Framework in Comparsion with Ambisonics

TL;DR

This study compares the spherical wavelet framework with Ambisonics, showing SWF's superior spatial fidelity but highlighting its limitations in representing continuous wave directions.

Contribution

The paper provides a detailed comparison of SWF and Ambisonics, including perceptual metrics and various layouts, revealing SWF's advantages and current limitations.

Findings

SWF is rated more similar to the reference than Ambisonics.

SWF's performance depends on sphere subdivision.

SWF cannot natively represent waves arriving at continuous directions.

Abstract

Recently, the Spherical Wavelet Framework (SWF) was proposed to combine the benefits of Ambisonics and Object-Based Audio (OBA) by utilising highly localised basis functions. SWF can enhance the sweet-spot area and reduce localisation blur while still enabling a sparse representation of the complete sound field, making storage and transmission more efficient. Initial vector analysis and listening test of SWF have shown promising results; however, these findings are limited to very specific conditions and do not include perceptual metrics. The present study investigates SWF in greater detail, comparing it with Ambisonics. The comparison was carried out using IACC, ITD, and ILD estimations, as well as listening tests with ecologically valid sound sources. Various reproduction layouts: regular polyhedron, t-design, and Lebedev grid with their corresponding Ambisonics orders and channel counts were evaluated. Results indicate that SWF is rated significantly more similar to the reference than Ambisonics is, in terms of overall spatial and timbral fidelity; however, it is considerably dependent on the subdivison of the sphere. Moreover, it cannot natively represent a wave arriving at a continuous direction. Possible solutions are proposed.