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Daily Personal Noise Exposure Level
This is more commonly known as Lep,d or Lex and is expressed in decibels.
The Lep,d represents the total noise received by an employee over the working
day and is therefore not only a function of the noise level but also of the time the
employee is exposed to it.
It is calculated using the Leq and is an essential parameter for Noise at Work
assessments.
The time period an employee is exposed to the noise level is commonly known as
the Exposure Time and this can be adjusted on your instrument to give partial
Lep,d levels for the employee. Exposure Time on your Sonus instrument is
displayed as ET. The Lep reading on your Sonus instrument is the Lep,d for the
given Exposure Time (ET) as set on the instrument. If an ET value is not entered
than the Measurement Time (MT) is used in the calculation instead.
As an example, an employee may undertake a total of 4 tasks throughout their
working day and each task taking 2 hours. The noise levels for each task will
therefore be recorded and the Exposure Time set to how long the employee is
subject to this particular task, in this case 2 hours.
The total Lep,d can then be calculated using the 4 partial Lep,d levels. This is
possible using the Exposure Calculator function within the software dBdataPro.
It is the total Lep,d that is used to compare with Exposure Action values and
Exposure Limit Value as stated in the Noise at Work Regulations. In the UK the
noise exposure limit and action values are as follows: -
80dBA = Lower Action Value
85dBA = Upper Action Value
87dBA = Limit Value
Remember that the longer the noise level is recorded over then the more
accurate the result will be although it is possible to take valid Lep,d readings
from short recordings of 5 minutes assuming all the variations in the noise
emissions are captured.
Also be aware that low noise levels with Exposure times over a longer period
may give the same Lep,d as noises with higher levels with Exposure Times over a
shorter period.
An example screen display may be: -
Lep 82.0