Comments on Draft ANSI S12.2, American National Standard on Criteria for Evaluating Room Noise

摘要

In 1995, American National Standard S12.2-1995 on room noise criteria was issued. Twomethods for specifying and evaluating room noise were presented, the NCB noise-criterioncurves (J.A.S.A. 86, 650-664, 1989) and the RC curves (Noise Control Eng. J. 45, 243-250,1997). The NCB curves were derived from the characteristics of hearing with emphasis onspeech interference level and loudness level, while the RC curves were derived fromexperimental studies in offices where the HVAC noise was low enough that there were nocomplaints from room occupants. The two sets of curves are incompatible at low frequenciesand low sound levels. The NCB curves assumed that the HVAC noise is free of surging andstrong turbulence. The RC curves demanded lower levels at low frequencies, thus allowingleeway for surging and turbulence. The new draft standard specifies two different sets of criteriacurves, namely NC and RNC. The NC set (Noise Control 3, 19-27, 1957) closely resembles theNCB curves but instead has found wide-spread use in practice, and the RNC (Noise Control Eng.J. 48, 85-96, 2000) bridges the differences between the NCB and RC curves, the amount ofbridging depending on the degree of surging and turbulence. This paper discusses the use of thenoise rating methods in the standard and their relation to the older methods