Coupled Volume Concert Hall Research Articles

Generative acoustics in architecture

The researchers share three studies in parametric, generative, and iterative architectural acoustics. (1) A real-time parametric model shapes a geometrically complex ceiling plane with grips in order to visualize first-order reflections so that early arriving strong reflections may be directed to the audience and late-arriving echoes may be avoided. (2) A ray-tracing software model pivots door openings so that a coupled volume concert hall can be calibrated to establish the “sweet spot” range of aperture sizes that are more likely to produce a double-sloped sound decay. (3) A custom-designed auralization software simulates sound transmission loss so that designers may hear the (relative) noise isolation of different assemblies.

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

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 DeltaL) 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 DeltaL, 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.

Quantifying the Double Slope Effect in Coupled Volume Room Systems

Coupled volume spaces are typically defined as a main volume connected to an auxiliary volume through an acoustically transparent aperture. Given certain architectural parameters, coupled volumes can exhibit a non-exponential sound energy decay, referred to in this paper as double slope effect (DSE). This paper provides an overview and comparison of several quantifiers of DSE. Four numeric DSE quantifiers, T30/T15, LDT/EDT, Decay Ratio, and ΔdB were used to analyze the energy decays produced in a computational model of an existing coupled volume concert hall. Each quantifier's ability to indicate changes in DSE was determined through comparative analysis. LDT/EDT was found to differentiate most between the levels of DSE in the sample decay curves. T30/T15 was also able to demonstrate changes in DSE, although not with the same level of sensitivity as LDT/EDT. Decay Ratio and ΔdB as determined from Bayesian analysis results did not indicate any DSE across the four cases studied; further research is recommended on applying Bayesian analysis to decay curves from realistic coupled volume scenarios.

Multivariable analysis of energy decay in coupled volume rooms: How can we objectively describe what we perceive in coupled volume performance spaces

The behavior of coupled volumes in room acoustics is commonly characterized by multiple slopes observed in sound energy decay curves, as measured (or modeled) using an omnidirectional receiver. This characterization is often limiting and can not adequately explain the change in character of sound energy decay with time that we perceive as listeners in music performance spaces that employ coupled volumes. By investigating energy decay as a function of several independent variables, including time, frequency, and direction of energy arrival, we seek to forge new objective measures that relate to what a listener actually hears in a coupled volume concert hall. We will discuss relevant geometry and materials of several coupled volume performance spaces designed by Artec Consultants Inc, describe subjective phenomena we have observed in these halls, and present results of our ongoing investigation of new objective metrics geared to better characterize coupled volume music performance spaces.

Comparison of Measured and Computer-Modeled Objective Parameters for an Existing Coupled Volume Concert Hall

This paper details the comparison of a built coupled volume concert hall and a computer-generated model of the hall. Coupled volume spaces typically have an auxiliary volume connected to the main volume through an acoustically transparent aperture. In this type of space, architectural parameters such as volume size and surface absorption can be designed to produce a non-linear reverberant decay, known as double-slope decay. Objective reverberation and clarity parameters were calculated for the sound fields measured in the built hall and predicted in the computer modeled hall. These objective parameters were compared between the two modalities for several configurations of the hall to determine the accuracy of the computer modeling prediction scheme for coupled volume spaces. The results showed a high level of computer model accuracy in the high frequency range, with differences in reverberation parameters being less than 1 just noticeable difference (jnd). Lower frequencies proved computer modeling to be less accurate, particularly for the clarity parameter, which had differences up to 8 jnd.

Double Sloped Decay: Subjective Listening Test to Determine Perceptibility and Preference

Can music listeners, both experienced and inexperienced, distinguish a double-sloped decay from a Sabine decay? Do they prefer the double slope? A simulated space, based on an actual built coupled-volume hall, was conceived in room acoustics software to create double sloped and classic Sabine auralizations. The simulated decays were compared with in situ measurements taken in a built coupled volume concert hall for validation. The impulse responses generated were convolved with an anechoic musical recording, grouped in pairs, and played for subjects. Participants listened to the recorded pairs over headphones and were asked to determine (1) if the two recordings sounded different, (2) which recording was more likely to have a double slope or had a more dramatic double slope, and (3) which of the two recordings they prefer. The more a recording diverged from a standard Sabine decay, the more likely the respondents were to identify that recording as having a double slope. When asked to identify a preference, subjects were no more likely to select a recording with a double-sloped decay, than a Sabine decay.

Absorption and aperture size effects on subjective response to complex computer modeled coupled volume systems

A typical coupled volume concert hall consists of a large, absorbent main volume linked to a smaller, reverberant auxiliary space through a series of acoustically transparent openings. This type of space can exhibit a nonexponential sound decay, a phenomenon that is referred to as the double slope effect (DSE). An imagined, realistic coupled volume concert hall has been computer modeled, and room impulse responses of the space have been obtained. Several configurations of the hall were conceived in which the absorption and aperture size were modified. Paired-comparison tests were conducted to determine listener preference for the sound fields developed from auralizations of the configurations. The results from this subjective testing were statistically analyzed using multidimensional scaling methods. The analysis showed that listener preference increased with decreasing DSE, with highest preference levels for low and medium DSE. These results will be presented and contrasted with objective parameters calculated from the room impulse responses of the computer-modeled configurations.

Subjective response to absorption and aperture size variations in complex computer-modeled coupled volume systems

Computer models of an imagined but realistic coupled volume concert hall have been made to obtain room impulse responses for several different configurations of the space. A coupled volume concert hall is typified by a large, absorbent main volume linked to a smaller, reverberant auxiliary space through a series of sonically transparent openings. Absorption and aperture size have been modified in this study to create each configuration of the virtual hall. Auralizations of the configurations have been used in paired-comparison tests to determine listener preference for the various sound fields, including some that exponentially decay and others that show a double-sloped decay. The results from this subjective testing were statistically analyzed using Thurstone Case V and multidimensional scaling methods. These results will be presented and contrasted with objective parameters extracted from the impulse responses generated by the computer modeled-configurations of the hall.

Coupled Volumes: Secondary Room Reverberance and the Double-Sloped Decay of Concert Halls

The coupled volume concert hall and its signature double sloped sound decay aim to partially reconcile the often-competing qualities of clarity and reverberance. A concert hall is conceived with a fixed geometric volume, form, and aperture size. A coupled volume is attached and its materiality is established as variable. Both statistical and geometric relative analyses suggest a highly sensitive relationship between the coupled volume reverberation time and the double-sloped condition.

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

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.

Exposure and materiality of the secondary room and its impact on the impulse response of coupled-volume concert halls

How does sound decay when one room is partially exposed to another (acoustically coupled)? More specifically, this research aims to quantify how operational and design decisions impact sound fields in the design of concert halls with acoustical coupling. By adding a second room to a concert hall, and designing doors to control the sonic transparency between the two rooms, designers can create a new, coupled acoustic. Concert halls use coupling to achieve a variable, longer, and distinct reverberant quality for their musicians and listeners. For this study a coupled-volume shoebox concert hall is conceived with a fixed geometric volume, form, and primary-room sound absorption. Aperture size and secondary-room sound absorption levels are established as variables. Statistical analysis of sound decay in this simulated hall suggests a highly sensitive relationship between the double-sloped condition and (1) architectural composition, as defined by the aperture size exposing the chamber and (2) materiality, as defined by the sound absorptance in the coupled volume. The theoretical, mathematical predictions are compared with coupled-volume concert hall field measurements and guidelines are suggested for future designs of coupled-volume concert halls.

Five sensitivities of the coupled volume/double sloped system

Stop chord measurements taken in an existing coupled volume concert hall, established statistically-based formulas, ray-tracing-software simulations, and headphone listening perception/preference studies imply a fickle relationship between the coupled volume concert hall, the double-sloped sound decay, and the listener. The two halls examined in this study suggest five sensitivities of the system: (1) To produce a double sloped sound decay, the coupled volume must be exceedingly more reverberant than the main hall to which it is attached. (2) To produce a double sloped sound decay, the sonic aperture linking the coupled volume to the main hall must be exceedingly small. (3) Maintaining low levels of background noise—always essential when designing spaces for music listening—is especially important if the double sloped impulse response is to be perceived above the noise floor. (4) Listeners who sit near the apertures probably hear something different than those who sit nearer to the center of the hall. (5) It is unclear whether subjects taking a paired comparison test prefer a double sloped auralization to a classic Sabine auralization.