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Parameter Explanations
Below are brief descriptions of the parameters available on all Sonus sound level
instruments. Refer to the glossary for more information if required.
Sound Pressure Level
The instantaneous Time and Frequency weighted rms sound pressure level in
decibels.
Depending on the instrument model the Time and Frequency Weighting may
both be changed.
The Noise at Work Regulations 2005 requires that frequency weighting ‘A’ is
used to determine noise exposures and that all peak values are taken using
frequency weighting ‘C’.
An example screen display may be: -
Equivalent Continuous Sound Level
This is more commonly known as Leq and is expressed in decibels.
It may be measured using Frequency Weighting ‘A’, ‘C’ or ‘Z’ and depending on
the Sonus model either of these can be selected.
The Leq is a time constantless parameter which means that it is calculated with
no Time Weighting applied.
Where an instrument is regarded as an integrating sound level meter, then Leq
will be available on the instrument.
To describe Leq, think of how the sound pressure level over a certain period is
likely to increase and decrease as people talk or maybe as machinery is being
used. Attempting to read this fluctuating sound on the meters display is
awkward.
Over the same period, the Leq will settle to an easy to read single value
representation having the same total sound energy of this varying noise over the
same time period. Measuring over longer time periods will therefore give more
accurate results.
LAF 91.3
Frequency Weighting
Time Weighting
