Spatial Sound Encoding Including Near Field Effect: Introducing Distance Coding Filters and a Viable, New Ambisonic Format

Abstract

Higher Order Ambisonics have been increasingly investigated in the past years, and found promising as a rational, scalable and flexible way to encode, transmit and r ender 3D sound fields. Nevertheless, studies concer ning virtual source imaging or natural 3D sound encoding mainly focussed on the directional encoding of plane waves , and neglected the near field effect of finite distance sources though it's present in any ordinary sound f ield. This paper highlights that with near field, the inf inite bass-boost affecting ambisonic components makes the currently accepted format unviable. By introducing from the e ncoding stage a near field compensation of reproduc tion loudspeakers, a viable, modified ambisonic format i s defined, distance-coding filters are designed, an d higher order ambisonic recording and synthesis become practicable.