Sound field synthesis for psychoacoustic research: In situ evaluation of auralized sound pressure level

Abstract

The use of virtual acoustic environments has become a key element in psychoacoustic and audiologic research, as loudspeaker-based reproduction offers many advantages over headphones. However, sound field synthesis methods have mostly been evaluated numerically or perceptually in the center, yielding little insight into the achievable accuracy of the reproduced sound field over a wider reproduction area with loudspeakers in a physical, laboratory-standard reproduction setup. Deviations from the ideal free-field and point-source concepts, such as non-ideal frequency response, non-omnidirectional directivity, acoustic reflections, and diffraction on the necessary hardware, impact the generated sound field. We evaluate reproduction accuracy in a 61-loudspeaker setup, the Simulated Open Field Environment, installed in an anechoic chamber. A first measurement following the ISO 8253-2:2009 standard for free-field audiology shows that the required accuracy is reached with critical-band-wide noise. A second measurement characterizes the sound pressure reproduced with the higher-order Ambisonics basic decoder, with and without max rE weighting, vector base amplitude panning, and nearest loudspeaker mapping on a 187 cm × 187 cm reproduction area. We show that the sweet-spot size observed in measured sound fields follows the rule kr≤N/2 rather than kr≤N but is still large enough to avoid compromising psychoacoustic experiments.