Spartan 821/721 Manual
Glossary
C-2
C Minus A, C–A
This measurement is an average level (L
avg)
of frequency-weighted values. It’s
application to the measured sound signal enhances the low-frequency components. It’s
the result of subtracting the A-weighted average level (L
avg
) from the C-weighted
average level (L
avg
) for the same measured signal.
Community Noise Equivalent Level (CNEL, L
DEN
)
L
DEN
, a rating of community noise exposure to all sources of sound that differentiates
between daytime, evening and nighttime noise exposure. The equation for L
DEN
is:
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 a penalty of 10 dB 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 a penalty of 5 dB 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.
Criterion Duration (Tc)
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
Criterion Sound Exposure (CSE)
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
Exchange Rate (Q), Exchange Rate Factor (q), Exposure Factor (k)
.
Standard: ANSI S1.25
Criterion Sound Level (L
c
)
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
L
DEN
10log10
1
24
------
10
Li 10
+
10
0000
0700
10
Li 10
0700
1900
10
Li 5
+
10
1900
2200
10
Li 10
+
10
2200
2400
+
+
+
=
CSE T
c
10
L
c
q
-----
=
