NTi Audio XL2 Sound Level Meter - Manual (Page 112)

112
Noise Curves
12 SIL Measurement Result
The speech interference level (SIL) result is shown at noise
curve types NC-2008 and NC-1995
1 . It is calculated by
averaging the octave-band sound pressure levels at 500
Hz, 1000 Hz, 2000 Hz and 4000 Hz. If the measured spec-
trum in any octave band does not exceed any of the octave
bands of that NC(SIL) curve, the spectrum is designated
NC(SIL). If one or more octave-band levels exceed the
NC(SIL) curve, then the NC curve number may differ to the
SIL value, as the NC rating for that spectrum must be de-
termined using the tangency method.
13 Large Fluctuations
This reports any large fluctuations at low frequencies
for the Room Noise Criteria RNC in accordance with
ANSI S12.2-2008. If one or more displayed measurement
results exceed the limits, then large fluctuations exist. Con-
cluding the LEQ levels in the octave frequency bands be-
low 300 Hz are automatically “penalized” at the RNC mea-
surement.
14 Correction Values
The noise curve type RNC uses these correction values
based on the measured fluctuation results to determine
the RNC curve result.