The Performance of a Public Address System as a Function of Auditorium Absorption

This paper summarizes the work done in connection with public address systems at the University of Texas, particularly in Gregory Gymnasium, an auditorium of one million cubic feet capacity, seating eight thousand people. The results of sound pressure measurements are given, as they show the nature of absorption in the auditorium and the resulting effect on acoustic regeneration and the frequencies at which “singing” takes place. Methods of reducing acoustic regeneration are discussed, which, in the case of Gregory Gymnasium, permit the public address system to establish a sound pressure of approximately twenty bars in the rear of the room, with microphone on the stage and a small orchestra playing.