BEAM-TRACING PREDICTION OF ROOM-TO-ROOM SOUND TRANSMISSION AND THE ACCURACY OF DIFFUSE-FIELD THEORY

Abstract

This paper validates the applicability of the classical diffuse-field prediction formula of room-to-room sound transmission used by many practitioners using energy- and phase-based beam-tracing models. An existing beam-tracing model for empty, parallelepiped rooms with specularly-reflecting surfaces has been adapted to predict room-to-room sound transmission between the source and receiver rooms separated by a common partition. For simplicity, initially sound transmission through the homogeneous common wall is modelled as one locally-reacting homogenous partition with frequency-independent transmission loss. The energy-based beam-tracing model has been validated in both source and receiver rooms through existing results from ODEON in the literature and by comparing the prediction results with CATT-Acoustic room-to-room sound transmission model. The phase-based beam-tracing model has been validated in the source room in comparison with COMSOL predictions. The new models are then used to investigate the accuracy of the classical diffuse-field formula in both source and receiver rooms. The diffuse-field prediction formula is found quite accurate in both the rooms in the beam-tracing prediction for cubic room shape and uniform absorption of all the room surfaces (i.e. for diffuse sound fields); however, it’s accuracy decreases significantly with changes in the shape of the room and the distribution of its surface absorption (i.e. more non-diffuse sound fields).