Procedure in Auditorium Design

Abstract

Discussion is confined to general-purpose auditoriums equipped with a stated number of fully upholstered chairs in a given floor area. Bounding surfaces of low absorptivity are stipulated. The design procedure is outlined as follows (1). The total absorption provided by the upholstered chairs, two-thirds audience, stage opening, and the hard room surfaces is estimated. From a chart that combines the Knudsen and Harris curve of optimum reverberation time with Beranek's curves of Sα as a function of volume and reverberation time there is found the volume that will yield optimum reverberation time with the total absorption estimated in the foregoing. (2) A ceiling profile that will, with the given floor area, yield the above optimum volume and, at the same time, give the most satisfactory distribution of reflected sound is developed by successive trials. A mathematical instrument that greatly facilitates the foregoing process is described. The rear wall is shaped to provide beneficial reflections to the rear seats. Optimum reverberation time and transmission efficiency are achieved in a minimum volume and without waste of sound energy in added absorption. Auditoriums designed according to the foregoing procedure have been found to provide excellent speech transmission and satisfactory hearing of music. No electrical amplification has been found necessary in auditoriums of upward of 1000 seats.