Influence of Diffusivity on the Transmission Loss of a Single‐Leaf Wall Free

Sound transmission loss tests on single‐leaf walls have shown deviations from theoretically predicted values calculated for a random‐incidence sound field acting on an infinitely large wall. Better agreement was obtained with the introduction of an upper bound for the integration with respect to the angle of incidence in order to obtain an average value for the transmission loss. Nevertheless, minor deviations persist, especially in the vicinity of the coincidence frequencies. In the present paper, the influence of diffusivity has been investigated by means of a random vibration method. The representation of the exciting pressure is given by the cross‐correlation function in time and space. For a true random‐incidence field, the function is given by $φρr(r,ω) = sin(kr)/kr$⁠, where k is the wavenumber and r the distance between the points under consideration. This has been generalized to fit the wide range of correlation relations met in practice. Computations show that relatively large deviations from the random‐incidence condition effect an upward shift of the transmission loss curve, but make only minor changes in its shape.