The Behavior of Sound in a Bounded Space

Consideration of the currently received theories of sound behavior in a room brought to light some severe anomalies. A concrete model of a rectangular room was constructed such that the number of boundaries could be varied. The steady-state and transient responses were investigated for different boundary configurations, and these were compared, firstly with predictions from the classical normal mode model, and secondly with digital computations from the impulse response, based on image model. The normal mode concepts were found to give a misleading picture of sound behavior, whereas the time-domain model was able to account for all results including those at frequencies comparable with the boundary dimensions where the normal mode model is usually substantiated. This model has also led to the prediction and verification of some unexpected phenomena in the fine structure of transient waveforms which, in the light of recent work on the hearing mechanism may well be responsible, in part, for our subjective response to an environment. The material in this paper is shared with this session and the F. V. Hunt Memorial Session I.