3-D Sound Image Reproduction Method Based on Spherical Harmonic Expansion for 22.2 Multichannel Audio

Kenta Iwai,Takanobu Nishiura,Hiromu Suzuki

doi:10.3390/app12041994

Abstract

In this paper, we propose a three-dimensional (3-D) sound image reproduction method based on spherical harmonic (SH) expansion for 22.2 multichannel audio. 22.2 multichannel audio is a 3-D sound field reproduction system that has been developed for ultra-high definition television (UHDTV). This system can reproduce 3-D sound images by simultaneously driving 22 loudspeakers and two sub-woofers. To control the 3-D sound image, vector base amplitude panning (VBAP) is conventionally used. VBAP can control the direction of 3-D sound image by weighting the input signal and emitting it from three loudspeakers. However, VBAP cannot control the distance of the 3-D sound image because it calculates the weight by only considering the image’s direction. To solve this problem, we propose a novel 3-D sound image reconstruction method based on SH expansion. The proposed method can control both the direction and distance of the 3-D sound image by controlling the sound directivity on the basis of spherical harmonics (SHs) and mode matching. The directivity of the 3-D sound image is obtained in the SH domain. In addition, the distance of the 3-D sound image is represented by the mode strength. The signal obtained by the proposed method is then emitted from loudspeakers and the 3-D sound image can be reproduced accurately with consideration of not only the direction but also the distance. A number of experimental results show that the proposed method can control both the direction and distance of 3-D sound images.

Highlights

Three-dimensional (3-D) sound field reproduction systems have become increasingly popular as video technology has advanced
To solve the problem for the original vector base amplitude panning (VBAP), we propose a novel 3-D sound image reproduction method based on spherical harmonic (SH) expansion [13]
We propose a novel 3-D sound reproduction method for 22.2 multichannel audio based on SH expansion [13]

Summary

Introduction

Three-dimensional (3-D) sound field reproduction systems have become increasingly popular as video technology has advanced. The 3-D sound field reproduction systems are classified with a psychoacoustics-based system and physical acoustics-based system. The binaural system and transaural system are traditional psychoacoustics-based systems [1]. Physical acoustics-based systems, such as wave field synthesis [1], are based on the Kirchhoff–Helmholtz integral and reproduce the sound field by using multiple loudspeakers. In [3], higher-order Ambisonics (HOA) is used to reproduce a 2-D sound field in the surrounding area by a circular loudspeaker array and cylindrical loudspeaker array. These researches depict the effectiveness of using loudspeaker arrays to achieve accurate sound field reproduction. We focus on a 22.2 multichannel audio [4] as multiple loudspeakers

Methods

Results

Conclusion