Sound-Strength Driven Parametric Design of an Acoustic Shell in a Free Field Environment

Abstract

Focusing on the issues of sound propagation in a free field condition and on the concept of uniform sound energy in an outdoor performance environment, our research aimed to develop a computer-aided process for the generation of reflective acoustic surfaces to be used as concert-shells, a computational design tool for acoustic form-finding. The project is ultimately aimed to investigate the acoustic potential of complex and doublycurved surfaces through the analysis of the Total Relative Sound Level / Strength parameter (G), with reference to the proposed values set by M.Barron, based upon the source-receiver distance and the subsequent subjective judgments on loudness. A simplified and fast ray-tracing acoustic simulation algorithm was developed in combination with parametrically controlled shape variations of the reflective surfaces. Sound energy uniformity evaluation function considering the direct and reflected sound components was written in order to define and evaluate the rate of distribution uniformity of sonic energy over an audience. This evaluation function was used in a genetic algorithm that enabled us to explore a wide set of surface morphologies which allowed us to isolate the fittest one to our specific uniformity requirements. At the end of the genetic search, an acoustic simulation plug-in called Pachyderm was employed with both NURBS and mesh-based acoustic simulations in order to validate the genetically selected surfaces with specific reference to G values. A further step of resultant data visualization and human selection was necessary to compare the output data and to evaluate the final surfaces from an architectural perspective. 32 Sound-Strength Driven Parametric Design of an Acoustic Shell in a Free Field Environment

Integrating acoustic simulation in architectural design workflows: the FabPod meeting room prototype

“…However, and perhaps more critically, as this workflow integrates analysis in the CAD design environment, this gives the potential to set up iterative optimization processes that could be linked to generative processes and this has been demonstrated in other research. 62,63 As more designers begin using computational methods and realizing their potentials, this type of workflow will become more prevalent.…”

“…Through the use of parametric or computational scripting, geometry modification can be linked to evaluation processes to allow for design performance optimization. 62,63 The workflow, as it is not fully integrated, is also difficult to use as a sketch tool; it does not allow for a quick analysis of many different options. Workflow 1 required a simplification of the complex geometry of the hyperboloid cells to a triangulated geometry (see Figure 14).…”

Measurements of stage acoustics in four configurations of an open-air performance acoustic shell

“…Acoustic shells [1,2] have been attractive for different open-air performances from the reuse of ancient spaces [3][4][5] to other experimental and commercialized solutions [6][7]. Besides the challenging acoustic conditions of the audience, concert halls need to provide a proper acoustic environment to the musicians on stage.…”

Émergence de morphologies pour l’acoustique des espaces de performance

“…Dans le cas de l'acoustique architecturale des salles de concert, l'optimisation d'une forme par un algorithme génétique monocritère a été effectuée en usant de la théorie de la préférence subjective en maximisant un indice composé de la somme des 4 facteurs orthogonaux (Sato et al, 2004 ;Ando, 2009) et par la maximisation de la puissance sonore (Palma et al, 2014). Un algorithme génétique multicritère a été utilisé pour l'optimisation d'une shoebox selon les indices acoustiques G, EDT et C80 3 estimés d'après simulation, sans considération pour les critères de spatialité (Echenagucia et al, 2014).…”