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

Abstract

This project utilizes computational modeling to study the effects of varying two architectural parameters, absorption ratio and aperture size, in a realistic coupled volume concert hall. Coupled volumes have been shown to exhibit non-exponential sound energy decay profiles, referred to as double slope effect. A number of objective metrics ͑T30/T15, LDT/T10, decay ratio, and ⌬L͒ have been used to quantify the double slope effect of the profiles generated in the virtual hall. T30/T15 and LDT/T10 showed similar trends across all hall configurations, indicating decreasing double slope effect with increasing coupled volume absorption ratio for each aperture size, and producing highest values at a specific aperture size for each absorption ratio. Generally, LDT/T10 provides finer resolution than T30/T15 when analyzing the decay profiles in this study. Results from the two metrics derived from Bayesian analysis, decay ratio and ⌬L, seem less consistent. Subjective testing has also been conducted to determine the effect of varying the two architectural parameters in the hall, and multidimensional scaling analysis shows that, in general, listener preference is inversely proportional to the level of double slope effect, with the highest levels of preference occurring at low and medium levels of double slope effect. Recommended design guidelines for coupled volume halls are provided based on these computational and subjective results.

Bayesian characterization of multiple-slope sound energy decays in coupled-volume systems

“…At three strategic receiver positions, the width of the aperture opening and absorption coefficients of the coupled volume surfaces are adjusted according to the geometrical and acoustic parameters published in Ref. 16. This section takes one representative case for aperture size 0.5% as an example result from CATT-ACOUSTIC TM software.…”

“…The study used a computational simulation produced using ODEON TM simulation software throughout the work to investigate a number of aperture sizes and absorption ratios between the main hall volume and a surrounding reverberation chamber, ranging from 0.5% to 10% opening area relative to the total surface area. 16 This paper utilizes the architectural and acoustic specifications 16 as listed in Table III, to create a geometrical-acoustics model using CATT-ACOUSTIC TM . The hall design is a generic implementation of the coupled chamber typology established by halls such as the Kultur und Kongresszentrum, Luzern and Meyerson Symphony Center, Dallas.…”

“…Some recent investigations in acoustics of coupled-volume systems directly utilized the approaches documented in early work [10][11][12] without examining their validity for coupled-volume applications. These investigations applied the ratio of two decay rates [14][15][16] to quantify double-slope decays. For example, a recent publication 16 has utilized a ratio between the late decay time (LDT) estimated from a level range between -25 and -35 dB and a decay time quantity T 10 between À5 and À15 dB, as a quantifier for characterization of non-single-exponential energy decay functions.…”

“…These investigations applied the ratio of two decay rates [14][15][16] to quantify double-slope decays. For example, a recent publication 16 has utilized a ratio between the late decay time (LDT) estimated from a level range between -25 and -35 dB and a decay time quantity T 10 between À5 and À15 dB, as a quantifier for characterization of non-single-exponential energy decay functions. However, experimentally measured room-acoustics data and computersimulated results from realistic concert hall and theater configurations have demonstrated that steady-state energy decays are often more complicated than a double-slope decay model.…”

Mismatches between objective parameters and measured perception assessment in room acoustics: A holistic approach

“…The choice of the particular type of spatial representation can be considered to be the most important part of the "modelling", and is applied together with a specific MDSalgorithm on the set of proximities. In the field of room acoustics, these techniques have been utilized in concert audition assessments [18], and more recently for a variety of purposes: to assess the perceptual similarity between auralizations, using both measured and simulated binaural room impulse responses [19]; for perceptions of double-slope decay profiles from auralized impulse responses of virtual hall configurations [20]; and for subjective evaluations with auralizations from on-site room impulse responses [21].…”