An efficient modal approach to characterize the diffuseness of the sound field in a rectangular room is presented. Using two simple descriptors, the correlation function and the spatial uniformity of the pressure field, a practical and convenient tool is proposed to study the diffuse field in the room. A precise criterion has been given in terms of the least permissible number of room modes to achieve an adequate diffusion. It has been shown that the criterion is in great accordance with the well-known “Schroeder frequency” limit for the diffuse field. Detailed calculations of the correlation function are presented to show the importance of the Δk/k correction terms to the well-known sin(kR)/kR prediction. A new closed form for the correlation function is thus derived. A discussion about the importance of having more than one descriptors is also presented. It is shown that a diffuse field can be established in a room with strong modal behavior under certain assumptions.

PACS. 71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.) - 71.10.Fd Lattice fermion models (Hubbard model, etc.) - 75.40.Mg Numerical simulation studies,

The modeling of the diffuse field sound transmission loss (TL) of apertures has been rarely considered in the literature. The aims of this paper are (i) to give a comprehensive review of the existing models, (ii) to propose a general efficient and rigorous numerical method to predict the diffuse field TL of apertures of rectangular and circular cross section, (iii) to provide the reader with numerical results regarding this indicator together with its relation with the normal incidence case for various geometrical configurations, and (iv) to conclude on the relevance of using such a sophisticated model compared to more classical normal incidence ones. The proposed approach is based on the description of the sound field inside the aperture in terms of propagating and evanescent acoustic modes. The radiation of the aperture is accounted for using a modal radiation impedance matrix. The coupled problem is solved in terms of modal contribution factors. The convergence of the approach is then investigated and the model is validated by comparisons with existing models for various configurations and excitations. Several numerical examples are provided regarding the normal incidence and diffuse field TL for various apertures and the relationship between these two indicators is discussed.

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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.

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