This paper discusses the determination of the sound reduction index of a flexible partition mounted between two rooms at low frequencies, where the diffuse approximation of the sound field is no longer valid.
In this frequency range, the modal density of the rooms is not sufficiently high and the statistical approach does not properly describe the behaviour of the system.
It is, then, of particular interest to investigate the feasibility of reproducing experimentally a diffuse acoustic pressure field using an array of loudspeakers in the sound transmission suite.
This approach would allow the transmission loss measurements to be performed without limitations at low frequencies.
An analytical model based on modal equations has been used to show the influence of the measuring facilities in the determination of the transmission loss factor.
T. Bravo and S. J. Elliott
Modelling and Experimental Measurements in Acoustics III, Chapter 3: Building Acoustics. Published in 2003 par Wessex Institute of Technology (WIT) Press. ISBN 1-85312-975-5
