Quantifying the Double Slope Effect in Coupled Volume Room Systems

Abstract

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.