Noise Dose : Definitions, Terms, Units and Measurements.
Noise Dose is the measured Sound Exposure Level normalized to an 8-hour working day.
% Dose is the Noise Exposure expressed as a percentage (%) of an 8-hour working day. In the UK the 100% level is 85 dBA using the
3 dB Exchange Rate. Dose% varies according to National Standards.
Daily Exposure Level - LEX,8h is the
Sound Exposure averaged over 8 hours.
The Noise at Work Directive 2003/10/EC : defines the following limit and action values:
Exposure Limit Values - ELV : the LEX,8h = 87 dB(A) and LCpeak = 200 Pa respectively.
Upper Exposure Action Values : the LEX,8h = 85 dB(A) and LCpeak = 140 Pa respectively.
Lower Exposure Action Values : the LEX,8h = 80 dB(A) and LCpeak = 112 Pa respectively.
LCpeak is the maximum value of the
C-weighted, instantaneous noise pressure.
see also Daily Personal Noise Exposure - LEP,d below.
LEX,8h is the Leq - Equivalent Continuous Sound Level corrected for the length of the working shift, in this case 8 hours.
Daily Personal Noise Exposure : LEP,d is the averaged A-weighted
noise exposure level for a nominal 8-hour working day and is for assessing the noise exposure of a employee during a working day. It is also known as LEX,8h.
LEP,d is calculated from the measured Sound Exposure, the Exposure Time and a Reference Time of 8 h.
If the Leq is measured over 8 hours then Leq and LEP,d and LEX,8h would all be the same.
The European Directive recommends LEX,8h is adopted from 2006 onward.
see also Leq - Equivalent Continuous Sound Level
DOHR : Dose per hour - shows the dose profile for each hour.
Dose% is the amount of noise expressed as a percentage of the normal allowable daily collected during a measurement on a worker with a noise dosimeter.
Dose% varies according to National Standards
Dose Badge : small device worn by operator to store fluctuating noise levels during working day. Similar to a Dosimeter.
Dose per Hour : DOHR : shows the dose exposure over each hour.
Dosimeter : a pocket sized instrument designed to be worn during all or part of the day as a personal monitor in order to check an operator's personal exposure to workplace -
: Sound Exposure Meter
EAL : Exposure Action Level
ELV : Exposure Limit Value
Estimated Dose : the exposure received if the measured level had existed for the specified Criterion Time.
Exposure Time : the time a person is exposed to noise during a workday - used for calculation of LEP,d - Daily Personal Noise Exposure.
Noise Dose : D : the
Sound Exposure expressed as a percentage (%) of a fixed level for the working day.
If the noise limit is 85 dBA and a person is exposed to a constant or
Sound Pressure Level of 85 dBA for eight hours, then the result is a 100% noise dose.
ISO use an energy-based average for noise dose calculation, based on the 3 dB
Exchange Rate. This means a noise level of 88 dBA has twice as much energy as a level of 85 dBA.
So if 85 dBA = 100%Dose = 8 hours exposure, then 88 dBA = 200% exposure so only a maximum of 4 hours is allowed per shift
The 3 dB exchange rate is also used in the UK, and the 8 hour average level is known as the
Daily Personal Noise Exposure LEP,d or
The Sound Exposure (in physical units) for the whole measurement duration of Dose is known as E (Pa².h)
Leq = 10 lg(Dose/100 x 8/T) + 85 dBA : where T = measurement time in hours.
LEX = 10 lg(Dose/100) + 85 dBA : where T = measurement time in hours.
The Noise Dose examples above assume the UK and EU default Criterion Time of 8 hours and Exchange Rate : Q = 3.
see also : Projected Dose and Threshold Level
Noise Dose Meter : Sound Exposure Meter also known as Noise Dosemeter and Noise Dosimeter.
Noise Dose per Hour : DOHR - shows the dose exposure over each hour.
Noise Dosimeter : a pocket sized instrument designed to be worn during all or part of the day as a personal monitor in order to check an operator's personal exposure to workplace noise - see Sound Exposure meter.
NProjDose : Projected Dose : uses the current
Noise Dose value, logged during the present measurement, to be projected forward to give the predicted 8 hour period, assuming the sound levels for the remaining time stays the same.
Threshold Level : most regulations specify that for the measurement of noise at work, the sound levels below a certain limit (the threshold) should be disregarded. A Noise Dose Meter, therefore only sums up the contributions from the levels above the threshold and uses these values to calculate the
Noise Dose parameters.
See also :
PSEM Personal Sound Exposure Meter
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