Audience and Chair Absorption in Large Halls. II

Abstract

Three alternate methods for considering the absorbing power of audience seating areas in the calculation of reverberation time in concert halls are treated. The absorption of audience seating, unoccupied and fully occupied, is expressed in terms of (1) equivalent sound-absorption coefficient αeq, (2) absorption per unit floor area (with edge corrections), αT, and (3) absorption per person aT. Recent data by Meyer, Kuttruff, and Roy, by Kosten, and by Kath and Kuhl are integrated with the author's data to yield new tables of αeq, αT, αS, αR, aT, and aS, where αR is the absorption coefficient of the nonseated areas of a hall, and αS and aS are the absorptions of unoccupied seating on a per-unit area and per-seat basis, respectively. The data show that total audience absorption increases in direct proportion to audience area (uniform distribution of persons and well-upholstered seats assumed), nearly independently of persons in the area. The halls studied have a range of seating densities from 5 to 8 sq ft of floor space per person and have normally diffuse sound fields.