Volume 128, Issue 3, September 2010
Index of content:
- ARCHITECTURAL ACOUSTICS 
A theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls128(2010); http://dx.doi.org/10.1121/1.3463802View Description Hide Description
This paper describes the development of a theoretical framework for quantitatively characterizing sound fielddiffusion based on scattering coefficient and absorption coefficient of walls. The concepts of equivalent scattering area, equivalent scatter reflection area, average scattering coefficient and average scatterreflection coefficient are introduced in order to express all walls’ capability of scatter in a room. Using these concepts and the mean free path, scatter-to-absorption ratio, mean scatter time and diffusion time are defined in order to evaluate degree of diffusion of a space. Furthermore the effect of spatial scattering objects to sound fielddiffusion is formulated. In addition the time variation of specular and scattered components in a room impulse response is formulated. The verification of these characterization methods was performed with computer simulations based on the sound ray tracing method. The results supported that the ideas presented are basically valid.
128(2010); http://dx.doi.org/10.1121/1.3463817View Description Hide Description
A numerical investigation is performed into the diffusive effects of cylinders positioned in front of a Schroeder diffuser. A regular line of cylinders is shown to offer notable improvements to diffusion from a periodic Schroeder device, provided lateral cylinder spacing is incommensurable with the Schroeder period width. Further investigation considers angular dependence and low frequency results in greater detail, as well as the effects on narrowband and modulated Schroeder devices. An optimization procedure is subsequently performed to investigate the effects of an irregular cylinder arrangement, which provides further diffusive benefits.
Room volume classification from room impulse response using statistical pattern recognition and feature selection128(2010); http://dx.doi.org/10.1121/1.3467765View Description Hide Description
Classification of the room volume from the room impulse response(RIR) can be useful in acoustic scene analysis applications, using RIR that is provided directly, or estimated from audio recordings. Current methods for estimating the room volume from the RIR require the source-to-receiver distance, and may be sensitive to differences in absorption. A room volume classification method is presented that does not require the source-to-receiver distance, and which is potentially robust to differences in absorption. Room volume features are defined that are related to the room volume and may be extracted from the RIR. Gaussian mixture models are trained to model room volume classes. Room volume is classified according to a maximum likelihood criterion that is normalized with a background model. Feature selection is performed with different classification error criteria. Both simulated and measured RIRs were examined, achieving an equal error rate of 0.1% and 19.1%, respectively.