Selected Problems in Architectural Acoustics

The paper discusses a number of undesirable acoustic effects together with measures which have to be taken to avoid or ameliorate these conditions. The first problem discussed deals with the absorption of high-frequency sound in air, the change of high-frequency reverberation with relative humidity of the air in a specific enclosure, and the average surface absorptivity required in this room to provide constant reverberation time for frequencies above 1000 cycles. Noted also is the energy reduction of high-frequency sound with change in reverberation and the air attenuation of high-frequency sound as a function of distance. In another problem the effects of sound interference are pictured as a function of the distance between source of sound and the point of observation and attention is drawn to the interference-reducing effect of surfaces not too highly reflective. After a comparison between "optic" and "acoustic diffusers," there is cited and pictured graphically the (Rayleigh) solution to the problem of the interference effect produced by a wall of sinusoidal cross section.