Transient modal behavior in coupled-room scale models

Abstract

This paper presents an experimental study of the behavior of low frequency sound propagation in acoustically coupled volumes. The experiments are carried out in an eighth-scale model of two coupled volumes with an automated high spatial-resolution scanning system. Both sound pressure and two-dimensional particle velocity are measured in terms of room impulse responses at each scanning position over densely defined two-dimensional grids covering the entire area of the two coupled rooms, thus enabling the visualization and analysis of sound energy flows in relation to time. Through these measurements, and with the aid of a simulation model, this paper will discuss the low frequency modal behavior of sound energy flows within the two coupled rooms of differing volumes with respect to both the time and frequency domain. Consequently, the distribution of vortices in the room due to the two-dimensional active sound intensity vectors calculated pointwise across the coupled space will be separately analyzed via mapping onto the aforementioned sound energy flow map. Rounding off the paper is a discussion on the specific instances where vortices may appear in one or both of the coupled rooms and the frequencies at which these modal phenomena exist.