Pulse Technique Applied to Acoustical Testing

Abstract

The lack of validity of the diffusion assumption makes it desirable to search for further means of assessing the acoustical properties of a room rather than a criterion based solely upon reverberation time. A pulse technique is devised to study transient sound in a room. An electroacoustic system was constructed for generating sound pulses and for receiving and recording such pulses after transmission through a room. Sound pulses were introduced into a room and the resulting sound field was measured at a number of positions. Acoustical testing includes the transient response in a lecture room, the determination of absorption coefficient of a wall, and the trace of a sound path in a room. A pulse statistical analysis was made. A steady-state decay curve was constructed using known values of reverberation time. The deviations from this steady-state decay in transient pulse measurements (over the peaks and troughs) were measured for 35 terms. A “mean value” decay curve was constructed from the average of the deviations. From the transient curve and the “mean value” curve, a rms deviation was obtained. The rms deviations for several positions in a lecture room and at different frequencies were computed.