Perception of loudness in directional sound fields

Abstract

An often utilized assumption in room acoustics is that the room produces a diffuse field, in which sound is uniformly distributed in space and arrives at the listener equally from all directions. This assumption greatly simplifies many calculations, e.g., Sabine's reverberation time (RT). However, the reverberant field, particularly the early part of the impulse response in typical concert spaces, is highly directional. Hence, the diffuse assumption leads to errors, for example, in the prediction of loudness when using omni-directional measures. Lateral reflections contribute to perceived loudness more than their omni-directionally measured sound energy. This is due the filtering of the head and torso, which amplify reflections from lateral directions more than others, particularly at high frequencies. Listening test results will be presented that demonstrate this effect. Spatial analyses of concert hall impulse responses demonstrate the practical applicability of this finding and make evident the relevance of the effect.