This Standard provides three primary methods for evaluating room
noise: a survey method, an engineering method, and a method for
evaluating low-frequency fluctuating noise. Two methods for
evaluating room noise—RC (room criterion) and NCB (balanced noise
criterion) curves—were the basis of the previous ANSI S12.2-1995
standard, and RC is included briefly for informational purposes in
Annex D. All of the methods assume that the measured noise is free
of tones. (ANSI S1.13-2005 Annex A gives an accurate method for
assessing the presence of prominent discrete tones using narrow
The three primary methods are:
1. The survey method that employs the A-weighted sound
2. The engineering method that employs noise criteria (NC)
3. The method for evaluating low-frequency fluctuating noise
using room noise criteria (RNC) curves.
This Standard also contains one ancillary set of criteria curves
for evaluating acoustically induced vibrations or rattles.
Requirements are given in the body of the Standard for
determining whether a:
1. Measured or estimated A-weighted sound level satisfies a
specified noise criterion.
2. Set of octave-band sound pressure levels satisfies a
specified noise criterion (NC) curve.
3. Time-series of octave-band sound pressure levels satisfies a
specified room noise criterion (RNC) curve.
4. Table of octave-band sound pressure levels that, when
modulated by fluctuations at low frequencies, may cause perceptible
vibrations or rattles in lightweight constructions.
Annex A presents examples of the use of RNC for evaluating
measured or estimated sound level spectra in rooms.
Annex B presents a discussion of RC, NC, NCB, and RNC
Annex C contains recommended noise level specifications for
various occupied activity areas.
Annex D contains the procedures for use of the room criteria
Annex E contains criteria for recording studios and other
No guidance is given for the selection of equipment or the
methods for measuring noise levels to be evaluated by the