| Abstrakt: |
Measurements were conducted to investigate the departure from linearity of sound decays in partially reverberant rooms-that is, rooms, such as are found in office buildings and residences, that are less reverberant than laboratory reverberation chambers. The extent to which the nonlinearities in the decay curves could be reduced by means of an ensemble-averaging procedure was determined. Decay curves for five partially reverberant rooms, ranging in size from 45 to 425 m3, were tape recorded and played back at reduced speed into a real-time analyzer. Decay measurements were also performed in the NBS 425-m3 reverberation chamber. It was found that ''smooth'' decay curves, displaying a curvature characterized by a monotonically decreasing decay rate, could be obtained provided that the ensemble averages included decays recorded at several source and receiver locations. Thus, the rate of decay at any point in time for partially reverberant rooms could be precisely and unambiguously determined. The magnitude of the curvature was such that the percentage difference between the early decay rate and the decay rate averaged over a 25-dB range varied from approximately 2% to 40%, with the greatest differences occurring in rooms containing an absorptive ceiling and floor or an opening connecting them to other rooms. [ABSTRACT FROM AUTHOR] |
