Casella CEL CEL-281 - Manual (Page 30)

A Projected Sound Exposure can be calculated when a sample ex-
posure has been obtained over a period that is different from the stand-
ard eight hour working day.
For example if the exposure determined during a measured part of the
standard day is expected to continue for the remainder of the day, the
sample can be projected for the whole day as follows:
E A,d = E A,Te
d
T e
(Pa 2
h )
Where:
E A , Te = Measured exposure over sample
period T
e in (Pa
2
h),
d = Length of actual working day in hours,
T e = Exposure time of sample in hours.
The CEL-281 calculates both % dose and projected % dose values for
an eight hour day only.
The relationships between sound exposure (E A ), noise dose (D) with
90 dB criterion, and daily sound exposure level (L EP,d ) for a normalised
eight hour working day are illustrated in Figure 1.
2.2.6 Distribution
This is a statistical determination of how often any particular event oc-
curs during a given survey found by dividing the total range of events re-
corded in a survey into separate events (or groups of similar events).
Such Statistical Distribution information is presented in the form of
a Histogram showing the number of times the event or group oc-
curred on a Frequency axis plotted against events or groups identified
on the other axis. Frequency is often replaced by Percentage Fre-
quency, which is the proportion of the total survey taken up by the
event.
Page 22 - CEL-281 Operator's Handbook
Introduction_