Casella CEL CEL-281 - Manual (Page 27)

Table 1: Valid pairs of criterion and threshold levels
Criterion
% @* %# @* & @* &" @* &# @* ' @*
Threshold
% @* ℵ ℵ ℵ ℵ ℵ ℵ
%# @* ℵ ℵ ℵ ℵ ℵ
& @* ℵ ℵ ℵ ℵ
&# @* ℵ ℵ
' @* ℵ
2.2.3 Threshold
Most sound exposure legislation requires that all noise measured during
the measuring period be included in the calculation of noise dose. How-
ever, some legislation specifies that only values that exceed some pre-
scribed threshold be considered, so that sound levels below this value
will not be included in the calculation.
In the CEL-281, results can be calculated and displayed for up to five dif-
ferent threshold levels: 70 dB, 75 dB, 80 dB, 85 dB, and 90 dB. The in-
strument will accept the selection only of valid threshold levels, i.e.
levels that are equal to or less than the criterion levels selected; refer to
Table 1 for valid pairs of levels.
2,2.4 Exchange Rate "Q"
The Equal Energy Exchange Rate is that part of the fundamental
physical relationship which states that when the Energy Content of a
sound is doubled, an increase of 3 dB in the sound exposure level will be
observed. Therefore to maintain an equal noise dose, the exposure time
must be halved
This is the relationship specified by most sound standards, and is equiva-
lent to Q = 3. However, some legislation seeks to define noise dose in
terms of the Estimated Risk Of Hearing Damage.
CEL-281 Operator's Handbook - Page 19
_Introduction