Objective assessment of concert hall acoustics using Temporal Energy Analysis

While for concert halls there are preferred ranges of values for the objective measures described in ISO3382-1, a method for comparing measured sound levels with theoretically expected values is proposed here. The theoretical values are based on the revised theory of sound level, with both measured and theoretical values plotted against source-receiver distance. The discussion concentrates on mid-frequency behaviour. The comparison can be made for early sound (less than 80 ms delay), late sound (greater than 80 ms delay), total sound level (G, strength) and the early-to-late sound index, C80. A composite of four graphs, one for each quantity, is suggested. The early and late levels can be considered from an objective standpoint as determined by the auditorium design, while the total level and early-to-late index relate to subjective response. Four case studies are presented which illustrate both typical behaviour and divergences from revised theory due to design features in the halls themselves. This Temporal Energy Analysis is proposed as an additional method for assessing acoustic behaviour with the advantage of illustrating behaviour at different locations within the auditorium.