Audience and Seat Absorption in Large Halls

Abstract

From detailed acoustical studies made in over 40 large concert halls and opera houses in 15 countries, absorption coefficients are derived for audience, chorus, and orchestra areas, unoccupied seating areas, plaster walls and wood walls. It is postulated that the absorbing power of a seated audience, chorus or orchestra in a large hall is proportional to the floor area it occupies. This postulate is validated for audience densities of between 4.5 and 8.5 sq ft per person, including aisles, and for halls with volumes between 200 000 and 1 500 000 cu ft. The “area” concept as opposed to the “per person” concept of audience absorption explains the serious differences reported repeatedly in the literature between reverberation times calculated during design and those measured after completion of the halls. This paper also presents graphical relations between empty and fully occupied hall reverberation times; shows the effect of seat design on empty hall reverberation times; and gives typical reverberation time vs frequency characteristics for fully occupied halls. The results of this study may not be applicable to rooms whose volume, shape, and materials are substantially different from the large concert halls and opera houses included this study.