1. LAeq,T or LAV measured &
2. Duration of exposure (minutes)
to get the Noise Dose and LAeq,8hr (aka TWA) calculation.
(Criteria Level = 85 dB, Exchange Rate = 3 dB, Threshold = none/80 dB)
|LAeq,T / LAV (dBA)||ExpDuration (minutes)||NoiseDose (%)||LAeq,8hr (aka TWA)|
(Reference: MOM Noise monitoring reports submission)
For Svantek noise dosimeters and Supervisor users, please example see below:
Example: 12 hrs work shift.
Instrument setting was set at 8 hrs.
Use "What if" panel inside Svantek Supervisor Software to adjust Projected Time to 12 hrs.
Use PrTWA (as LAeq,8hr) in noise monitoring report.
Ensure that noisy period of work is sampled during dosimetry measurements. Measurement duration should be about 80% of work shift as mentioned inside WSH Guidelines for HCP (2nd revision, 2014), pg35.
"For practical reasons, it may not be possible to measure the noise levels over the entire working day. In these cases, measurements should as far as possible, be taken during the major part of the day (~80% of the work shift) and at least cover all significant periods of noise exposure."
Noise dose (D) is used as an indication of a percentage of the permissible noise exposure limit.
It is defined as the sum of fraction of exposure time at specific sound pressure level (ti) to the permissible exposure time (Ti) at that level.
Dose is expressed as a percentage of a maximum permissible daily exposure to noise. The sum of the fractions is the noise dose expressed in % with 100% being the permissible criterion sound level.
The permissible exposure time (T) in hours is related to the exposure sound pressure level (SPL) by the following formula.
*source: WSHC (2013) Workplace Safety and Health Guidelines - Statutory Medical Examination. (page 35)
Further readings about Leq and Lavg, "A practical comparison of occupational noise standards - TINGAY and ROBINSON, 2014, Inter-noise 2014"
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