Room transfer function measurement from a directional loudspeaker

Abstract

Room transfer function (RTF) is the room response observed at a particular listening point due to an impulse generated from an omnidirectional point source. Typically, measured RTFs in practice are often erroneous due to the directivity of the measurement loudspeaker. This paper formulates a spherical harmonic based parameterization of the room response for a directional loudspeaker, and provides a direct approach to derive the point to point RTF using measurements from a directional loudspeaker. Simulation results are presented for 2 directional loudspeakers with an active frequency bandwidth of 200 − 4000 Hz.

Spherical harmonics based generalized image source method for simulating room acoustics

“…Note that for a given loudspeaker, its order can be determined by N ¼ dkRe, whereR is the radius of the smallest sphere enclosing the physical speaker. 34,35 We assume the order N and outgoing soundfield coefficients b nm (k) are known for the loudspeaker of interest. Based on spatial soundfield theory, the spherical harmonic coefficients beyond this order can be assumed to be negligible.…”

3D exterior soundfield capture using pressure and gradient microphone array on 2D plane

“…The spherical harmonic expansion of pressure for an exterior soundfield at a point (r, θ, φ) produced by a source at the origin O can be derived as [13] …”