2.5D Sound Field Reproduction Using Higher Order Loudspeakers

Abstract

Using 3-Dimensional (3D) sound sources as secondary sources to 2-Dimensional (2D) sound field reproduction, it is termed 2.5-Dimensional (2.5D) sound field reproduction which is currently drawing broad interest in acoustic signal processing. In this paper we propose a method to reproduce a 2D sound field, using a circular array of 3D High Order (HO) loudspeakers, which provides a mode matching solution based on 3D wave field translation. Using the spherical addition theorem, we first obtain a spherical harmonics representation of a 2D sound field reproduced by an array of HO loudspeakers. Then, the corresponding relationship between the reproduced sound field and the desired sound field is established by spherical/cylindrical harmonic expansions. Finally, the modal weights of HO loudspeakers are designed by using a least squares method. Simulation results show that the proposed method extends the reproduction region and significantly reduces the required minimum number of loudspeakers over the other referenced methods.

Reproduction of Nearby Sound Sources Using a Modified Distance Coding in Higher Order Ambisonics

“…where the truncation order /2 r max M er k    [13], e = exp(1) = 2.718 and K max is the maximum wavenumber corresponding to maximum frequency. J m (k s r)e imϕ is the basis function of cylindrical harmonic expansion.…”

“…, is given by P r (x) K = P d (x) K (14) By introducing (13) and (10) β s (17) where # represents the Hermitian Transpose, and I is a [(2M+1)×(2M+1)] identity matrix. Note that γ is the regularization control parameter and γ = 0 indicates the minimum energy solution of (17).…”

2.5D Near-field Reproduction in Higher Order Ambisonics

“…Recently, HOA has been related to the implementation of 2.5D sound field reproduction, where HOA is based on the cylindrical/spherical harmonic representations of sound fields. In these methods, 3D higher order loudspeakers [11] and 3D point sources are selected as the secondary sound sources. Nevertheless, most implementations of 2.5D HOA don't consider the near-field reproduction problem.…”