Single-value frequency-average measures of early decay time and clarity index to predict reverberance and clarity

Abstract

The most accepted acoustical parameters for the assessment of concert hall acoustics are summarized in the Annex A of the ISO 3382-1 standard, along with recommendations that are important for the practical application of these parameters. These recommendations have their origin in the practical experience of acoustical consultants and a few scientific studies, and further research is needed to properly validate them. In particular, more information is needed on how to average the octave-band values of acoustical parameters to obtain single-value frequency-average measures (SVFA) that are better correlated with the associated perceptual aspects. In this study, SVFA measures of early decay time (EDT) and clarity index (C80) were obtained by means of a listening test in which 24 subjects rated a set of stimuli in terms of reverberance and clarity. The participants listened to auralizations of orchestral music convolved with measured spatial room impulse responses in an anechoic chamber using third-order Ambisonic reproduction. The results of the listening test indicate that the mid-frequency, 500 and 1000 Hz, octave-band average of EDT and the average of the 4000and the 8000 Hz octave bands of C80, have the highest sensitivity in the prediction of reverberance and musical clarity, respectively.