Acoustical Features of the Addition to the Physics Building at the University of Texas

Detailed description is given of the acoustic designs used in the addition to the Physics Building at the University of Texas. Sound absorption is included in the lecture rooms in the form of an acoustic blanket behind a pierced glazed brick wall to give a broadly resonant absorption with maximum coefficient at 500 cps of 0.60, reducing to 0.40 at 125 cps and to 0.25 at 4000 cps, and in the form of a slit absorber having a resonance at about 400 cps with coefficient of 0.55, reducing to 0.45 at 125 cps and 0.33 at 4000 cps. Sound diffusion and projection in these lecture rooms is secured by sound reflectors over the speaker's position, nonparallel side walls, and light fixture coves in the ceiling. Sound absorption in some of the laboratories is provided by use of functional absorbers each using an acoustic blanket free on one side and confined by a perforated hardboard on the other. Measurements on two such rooms show a resonant absorption is obtained with peak frequency at 500 cps, and with apparent absorption coefficient near unity at the peak, dropping to 0.70 at 125 cps and to 0.50 at 4000 cps.