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Acoustic simulations of complex virtual environments typically are created with geometrical-acoustics techniques. Such simulations can be augmented with edge diffraction modeling for improved accuracy, but not without a significant increase in processing time due to the additional propagation paths which must be considered and the computational complexity of the diffraction calculations. However, for a given modeling scenario, the contribution of a diffracted path to the overall impulse response can vary over a large range, suggesting that certain diffracted paths can be ignored, or culled, to reduce processing time with a limited effect on the accuracy of the simulation. In this talk, we first analyze the effects of diffraction culling through a precomputed, amplitude-based ranking scheme. We then describe a simple procedure for identifying and culling insignificant diffraction components during a virtual-acoustic simulation which approximates the performance of the precomputed ranking. Through numerical and subjective analysis, we show that a significant percentage of diffracted paths can be ignored if the retained paths are those which lead to the highest-amplitude diffraction components, although the audible effects of such diffraction culling are dependent on the input signal.

Spin classes utilize sound systems that generate levels in excess of 115 dBA, with subwoofers to match. Gyms located in office buildings feature Olympics style weight lifting technique that involves dropping 200 lb (or more) barbells from shoulder or overhead positions. Medicine balls get thrown at walls and floors. More “typical” sources of airborne and structureborne noise—treadmills, aerobics classes, weight machines, and the like—contribute to the din. The authors will present experiences and lessons learned from actual field experience with fitness centers located in commercial, residential, and mixed-use developments. Data will be presented on the effectiveness of mitigation methods installed in real buildings to attenuate airborne and structureborne noise. The session will include a discussion of the various types of fitness franchises and associated acoustic concerns, illustrated by case study examples from the authors’ acoustical consulting experience.

Auralization has become a valuable tool to explore the acoustics of spaces and activities that no longer exist. Generally, acoustical archaeology has explored a fairly limited number of sources in a space to determine specific acoustical aspects of the sound of the spaces and to separate intentionally designed acoustical phenomena from the often unintended effects of the architecture. We have expanded this technique to recreate the entire soundscape of a specific event, in this case John Donne’s 1622 Gunpowder Plot sermon at Paul’s Cross, outside St. Paul’s Cathedral in London as it was prior to the fire of 1666. This work augments ambisonic auralization techniques with techniques borrowed from computer-aided music composition and audio production to create an immersive acoustical environment for the purpose of exploring the experience of listeners at many positions in a crowd that can be varied in size in real time. The paper outlines the role of geometric acoustics modeling, real-time convolution, randomized and statistically derived sound event triggers, and other techniques employed to auralize a soundscape that includes the sermon, crowd response, and the ambient sounds of pre-Industrial London.