Volume 125, Issue 3, March 2009
Index of content:
- ARCHITECTURAL ACOUSTICS 
125(2009); http://dx.doi.org/10.1121/1.3075560View Description Hide Description
With the aim of quantifying sound-field uniformity in spaces of relatively low volume, four different configurations in terms of acoustic treatment and sound-field diffuseness were constructed and tested. In a diffuse sound field, reflections are not strongly correlated both to the original sound and to earlier reflections. The degree of correlation is embedded in the impulse response structure, but is not trivial to identify. The room impulse responses exhibit self-similarity and therefore may be treated as multifractal signals characterized by a singularity spectrum. The singularity spectrum contains a wealth of information about the acoustic field established in the room. The width of the singularity spectrum, in particular, is directly related to the complexity of the impulse response structure. The uniformity of the sound field in the room can be evaluated by examining the variation of the singularity spectra with position. A new definition for sound field diffuseness is given that is not based on the concept of the energy density. The proposed method is simple to apply, statistically robust, and provides a measure of diffusion independent of the room reverberation.
Analytical and experimental investigation on transmission loss of clamped double panels: Implication of boundary effects125(2009); http://dx.doi.org/10.1121/1.3075766View Description Hide Description
The air-borne sound insulation performance of a rectangular double-panel partition clamp mounted on an infinite acoustic rigid baffle is investigated both analytically and experimentally and compared with that of a simply supported one. With the clamped (or simply supported) boundary accounted for by using the method of modal function, a double series solution for the sound transmission loss (STL) of the structure is obtained by employing the weighted residual (Galerkin) method. Experimental measurements with Al double-panel partitions having air cavity are subsequently carried out to validate the theoretical model for both types of the boundary condition, and good overall agreement is achieved. A consistency check of the two different models (based separately on clamped modal function and simply supported modal function) is performed by extending the panel dimensions to infinite where no boundaries exist. The significant discrepancies between the two different boundary conditions are demonstrated in terms of the STL versus frequency plots as well as the panel deflection mode shapes.