Coupled Volumes: Aperture Size and the Double-Sloped Decay of Concert Halls

Abstract

The coupled-volume concert hall and its signature double-sloped sound decay attempt to reconcile the often-competing qualities of clarity and reverberance. By wrapping a room with another more reverberant room, and allowing for apertures to control the sonic transparency between the two rooms, designers use coupling to provide a sound field that is variable, longer, distinct, and performance-piece-specific. For this study a coupled-volume concert hall (based on an existing hall) is conceived with a fixed geometric volume, form, and materiality. Aperture size is established as variable. The simulated hall undergoes statistical and geometric (ray tracing software) analysis. Results show disparity in the absolute decay patterns projected by the two methods; however, both statistical and geometric relative analyses suggest a highly sensitive relationship between the aperture size exposing the coupled-volume and the double-sloped condition. To test the model, simulations are compared to real-room measurements taken in a coupled volume concert hall. I. INTRODUCTION: Researchers have established an inverse relationship between the important acoustical qualities of clarity and reverberance. 1,2 Once considered anathema to quality acoustics, 3 the double-sloped sound decay has recently received attention as a possible method of simultaneously achieving clarity with reverberance in concert halls. By allowing a musical note to decay rapidly at first, each successive note may be perceived as a *Expansion of: Ermann, M., Johnson, M., and Harrison, B., "Aperture size, materiality of the secondary room and listener location: Impact on the simulated impulse response of a coupled-volume concert hall," (From the 145 th meeting of the ASA, Nashville).

Optimum absorption and aperture parameters for realistic coupled volume spaces determined from computational analysis and subjective testing results

“…[7][8][9][10][11][12][13][14] Of particular note, Nijs et al 9 compared scale and computational model results of coupled volume spaces and listed several best practice techniques for increasing the fidelity of the computational simulations. These techniques have been implemented in the computational work described in this paper.…”

“…Harrison and Madaras 10 found that T30/T15 values were highest for smaller aperture opening sizes, and increased with larger coupled volume sizes. Ermann 13 used a similar ratio of T60/ T15 in his work, wherein he studied the effect of aperture size and coupled volume absorption on DSE using numerical and CATT ACOUSTIC ͑version 8.0b͒ models of an imagined coupled volume concert hall. His work showed that having an average absorption coefficient ͑␣ ͒ in the coupled space less than 0.02 ͑␣ Ͻ 0.02͒ produced significantly higher T60/ T15 values than 0.02Ͻ ␣ Ͻ 0.05.…”

On the use of a diffusion model for acoustically coupled rooms

“…Since Davis's initial work, 1 several models have been proposed such as statistical theory, 1-8 statistical energy analysis, 9,10 modal theory, [11][12][13] finite-element methods, 14 and ray-based models. 8,[15][16][17][18][19][20][21][22] Despite being based on the diffuse-sound-field theory assumption, the statistical theory has been compared satisfactory with experimental 2,15,20,21,23 and numerical results. 8,21,22 Nevertheless, different authors question the ability of the statistical theory to deal with room modes, geometric and acoustic details, as well as nondiffuse sound field.…”

Simulated Sound-Fields in a Multi-Configurable Auditorium

“…However, as a further aspect of the widespread use of computers in architecture (Oldham, Rowell, 1987), computer simulations are replacing these physical models since their algorithms are becoming not only easier to use but also cheaper and more accurate. Nowadays, the wide range of existing commercial computer programmes, whose validity can be directed towards a variety of scientific aspects (Ermann, 2005;Rychtáriková et al, 2011), incorporate highquality auralizations. A major effort is being invested in research for the refinement of these auralizations (Torres et al, 2001;Calamia et al, 2008; Zahorik, 2009) in acoustic virtual-reality applications, and for the recreation of the sound of both multiple future virtual acoustic environments of spaces and of ancient scenarios for archaeological purposes (Vassilantonopoulos, Mourjopoulos, 2009).…”