Abstract:

ANSI S12.2-1995, ``Criteria for Evaluating Room Noise,'' permits two different sets of criterion curves for evaluating room noise---room criterion (RC) and balanced noise criterion (NCB)---with little guidance as to the selection. These different procedures can have significant impacts on the cost of designs, especially in the low-frequency regions, since the difference in the criteria is more than 10 dB in the 16- and 31-Hz octave bands at lower levels. The authors suggest there are sufficient data to support a modification to ANSI S12.2, resulting in a single evaluation procedure based on the strengths of each of the two existing procedures. The authors suggest establishing room criterion curves for steady noise without abnormal temporal or spectral characteristics, with correction factors for noises with abnormal features. The suggested criteria for steady noise are the NCB curves based on time-average octave band sound pressure levels, and as a starting point, the correction factors for low-frequency tones and fluctuation differences between the NCB and RC curves. Analyses of currently funded research and re-examination of existing cases can determine the exact correction factors and measurement techniques to quantify these abnormal characteristics. A revised ANSI S12.2 could have basic criterion curves for steady, continuous, and broadband room noises, which could be used for design with correction factors to these basic criterion curves for sounds with abnormal characteristics. [See NOISE-CON Proceedings for full paper.]