A new approach to low-frequency room noise criteria

Abstract

There are three different and conflicting room criteria methods that are widely used by consultants today: room criterion (RC), balanced noise criterion (NCB), and noise criteria (NC). The RC procedure is documented in ANSI S12.2-1995 ‘‘Criteria for evaluating room noise’’ and the ‘‘1995 ASHRAE Applications Handbook;’’ the NCB procedure in ANSI S12.2; and the NC ‘‘tangency’’ method in the ‘‘1991 ASHRAE Applications Handbook.’’ There are significant differences in the three criteria, especially for low frequencies, which can impact the costs both of new designs and of remedial actions to existing facilities. In order to promote a resolution to these differences, NOISE-CON96 and NOISE-CON97 held special technical sessions on room noise criteria. Based on our analysis of published research and on experiences dealing with other noise sources, the authors suggest an approach to resolve the low-frequency differences: (1) establish basic room criterion curves for noises without abnormal temporal or spectral characteristics, and (2) apply correction factors to the measured data to account for abnormal features before comparison to the basic criterion. This paper presents details of the suggested approach, the status of revisions to ANSI S12.2 and to the ASHRAE handbook, and other ongoing research.