Vox -01 Operating Manual page 50

8.2. Noise curves
The "noise curves" module implements a series of measurement methods to evaluate noise
levels, based on sets of standardized spectral curves. The objective of these methods is to
set criteria in terms of a single-number rating, while taking the spectral characteristics of
noise into account.
The following methods are implement
Noise Rating (NR). This is an ISO-standardized (ISO-1996) method. Although the
method is being pushed into the background by successive updates to the relevant stand-
ards, it is still seeing a fair amount of use, in particular in Europe.
Noise Criteria (NC). This method is frequently used in the United States, mostly for
evaluating background sound in buildings and for specification of desired levels in
advance of construction. Different versions of the NC have been in circulation since the
1950s; the VOX-01 implements the version standardized through ANSI S12.2:2008.
Preferred Noise Criterion (PNC). This is a variant of NC, not included in ANSI S12.2,
but proposed originally by Beranek et al (1973) to yield a better correspondence with per-
ceived annoyance by putting more emphasis on the lowest frequency bands and highest
frequency bands.
Balanced Noise Criterion (NCB). Standardized through ANSI S12.2:1995, similar in pur-
pose and application to NC; apparently intended upon its introduction to replace NC.
Room Criteria (RC). This method is primarily used to quantify noise from HVAC systems
in buildings. In addition to the single number rating (e.g. RC-35) a spectral classification of
the signal is also given: Neutral (N), Hiss (H), Rumble (R) and Rattle and Vibration (RV).
Room Criteria mark II (RCII). Updated version apparently intended to eventually replace
RC curves.
The Room Noise Criterion (RNC) method is currently not implemented on the VOX-01.
Each method has its own series of preferred limits, depending on the purpose of the room
in which it is measured. ANSI S12.2 contains table of recommend maximum NC and RC
values, and additional information is available through an abundance of online resources.
A full list of these recommend limits is beyond the scope of this manual.
As part of the calculations, various intermediate metrics are calculated including the Speech
Interference Level (SIL).
50 VOX-01 Operating Manual