Sound transmission loss of rectangular and slit-shaped apertures: Experimental results and correlation with a modal model

Abstract

Among noise control techniques, enclosures are widely used. It is known that enclosure acoustic efficiency is strongly influenced by the presence of openings or leaks. Modeling of diffuse field sound transmission loss (TL) of apertures and slits is therefore critical when the enclosure acoustic performance characteristics need to be predicted with confidence either for design or for modifying existing enclosures. Recently, a general model for diffuse field sound TL of rectangular and circular apertures has been developed and validated with respect to existing analytical or numerical models. This paper presents an experimental validation of this new model. The aim was to develop a simple, reliable tool for predicting enclosure insertion loss using statistical energy analysis. Twelve out of the 15 test configurations were found to be reliable and were compared with theoretical models, which in fact correlate closely (without adjustment) with the experimental work.

Sound radiation from an aperture in a rectangular enclosure under low modal conditions

“…The next step is the calculation of the velocity distribution at the aperture [Eq. (10)]. Finally, the pressure outside the enclosure can be found using Eq.…”

“…7,8 Some of the referenced models could be applied to calculate the radiation from apertures on enclosure boundaries if multiple oblique incidence plane waves are considered in the incidence region as was experimentally demonstrated by Oldham and Zhao 9 for circular and slit-shaped apertures or, more recently, by Trompette et al, for rectangular and slitshaped apertures. 10 Other work has addressed the effect of the reverberant room in the incidence region, as, for example, Davy,11 who considered an aperture in a thin wall of a 2D room. In his paper, the sound pressure at the aperture is a continuous function of the incidence angle and the sound absorption coefficient of the room, and the impedance of the aperture was assumed to be a function of the radiation efficiency.…”

Prediction of the spatial characteristics of higher mode sound transmission through a periodic slit screen

“…It was also noted that there was strong cross modal coupling between the (0,0) plane wave mode and higher order even-even modes and that for aspect ratios greater than one, the transmission models based only on plane waves may not be sufficient even at low frequencies, due to the low values for the cut-on frequency of the first higher order mode. Sgard and co-researchers [10] continued the analysis by performing experimental validation tests. Results were presented for both rectangular apertures and slits and good comparison was found between measurements on apertures and estimated results.…”

Modal-based prediction of sound transmission through slits and openings between rooms

“…Finally, in [28] a more general model that can take into account any opening shape is proposed. The presentation of the model is preceded by an extensive literature review and comparisons with experiments in [31].…”