Comments on draft ANSI S12.2, American National standard on criteria for evaluating room noise

Abstract

In 1995, American National Standard S12.2‐1995 on room noise criteria was issued. Two methods for specifying and evaluating room noise were presented, the NCB noise‐criterion curves [J. Acoust. Soc. Am. 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 on speech interference level and loudness level, while the RC curves were derived from experimental studies in offices where the HVAC noise was low enough that there were no complaints from room occupants. The NCB curves were applicable to rooms ranging from concert halls to factory spaces, while the RC curves were largely restricted to office, hospital, and residential spaces. The two sets were incompatible at low frequencies and low sound levels. The NCB curves assumed that the HVAC noise was free of surging and strong turbulence. The RC curves demanded lower levels at low frequencies, thus permitting some degree of surging and turbulence. The new draft standard specifies two methods for evaluating room noise, the NC [Noise Control 3, 19–27 (1957)] and the RNC methods [Noise Control Eng. J. 48, 85–96 (2000)]. The former (NC) have found widespread use and the latter (RNC) bridges the differences between the NC (and NCB) and the RC criteria curves. This paper comments on the promise of the new RNC method and compares measured data were available.