Larson Davis SoundAdvisor 831C Reference Manual page 204

Community Noise
Equivalent Level
(CNEL, L )
den
Criterion Duration
(Tc)
Criterion Sound
Exposure (CSE)
Criterion Sound
Level (L )
c
Daily Personal
Noise Exposure
(L )
EP,d
SoundAdvisor Model 831C
A rating of community noise exposure to all sources of sound that differentiates
between daytime, evening and nighttime noise exposure. The equation for it is

1
----- -

L = 10log
24
den 10

The continuous equivalent sound level is generally calculated on an hourly basis
and is shown in the equation as L. The levels for the hourly periods from midnight
to 7 a.m. have 10 added to them to represent less tolerance for noise during
sleeping hours. The same occurs from 10 p.m. to midnight. The levels for the
hourly periods between 7 p.m. and 10 p.m. have 5 added to them to represent a
lessened tolerance for noise during evening activities. They are energy summed
and converted to an average noise exposure rating.
It is the time required for a constant sound level equal to the Criterion Level to
produce a Noise Dose of 100%. Criterion Duration is typically 8 hours.
Example: If the Criterion Level = 90 dB and the Criterion Duration is 8 hours, then
a sound level of 90 dB for 8 hours, will produce a 100% Noise Dose. See Noise
Dose. Standard: ANSI S12.19
The product of the Criterion Duration and the mean square sound pressure
associated with the Criterion Sound Level when adjusted for the Exchange Rate.
It is expressed in Pascals-squared seconds when the exchange rate is 3 dB, where
q is the Exchange Rate Factor. See Exchange Rate.
Standard: ANSI S1.25
It is the sound level which if continually applied for the Criterion Duration will
produce a Noise Dose of 100%. The current OSHA Criterion Level is 90 dB.
Standard: ANSI S12.19
It is the level of a constant sound over the Criterion Duration that contains the
same sound energy as the actual, unsteady sound over a specific period. The
period is generally shorter, so the sound energy is spread out over the Criterion
Duration period.
Example: If the Criterion Duration = 8 hours and the specific period is 4 hours and
the average level during the 4 hours is 86 dB, then the L
T 2


1
 
-- -
L = qLog 10

avg 10
T

T 1

0700 1900
 
  10  
L + 10 L
i i
10 + 10
0000 0700
CSE = T c 10


 L p t    q 

dt



2200 2400
 
  10 
10 L + 5
i
+ 10 + 10
1900 2200
L c q 
= 83 dB.
EP,d

  10 
L + 10

i

C-2