# Acoustic Glossary

## Noise Dose Terms, Definitions, Units, Measurements

The Noise Dose Criteria, in the UK is currently 85dBA and if anyone is exposed to a time weighted average noise level of 85 dBA during an 8-hour period their noise dose is 100%.

Employers must assess and identify measures to eliminate or reduce risks from exposure to noise, in order to protect the hearing of their employees.

The British and ISO Standards are based on the 3 dB exchange rate, which means noise levels of 88 dBA have twice as much energy as levels of 85 dBA. It follows that if 85 dBA = 100% noise dose, then 88 dBA = 200% noise dose and therefore the maximum exposure time is restricted to 4 hours per shift - ergo twice the level means half the time

Noise Dose is the total sound exposure normalized to an 8-hour working day.

The 8 hour level is known as the LEP,d (daily personal noise exposure) or LEX,8h.

The Noise Dose (in physical units) for the whole measurement duration of sound exposure is known as E (Pa2.h)

For a given period of time, an increase of 10 dB(A) in sound pressure level corresponds to a tenfold increase in the noise dose.

1 Pa2·h = 100% Noise Dose = 85 LAeq(8 h) = 85 dBA for 8 hours.
0.1 Pa2  =  74.9 LAeq,8 h
0.2 Pa2  =  78.0 LAeq,8 h
0.5 Pa2  =  81.9 LAeq,8 h
1 Pa2  =  84.9 LAeq,8 h  =  100% Noise Dose
2 Pa2  =  88.0 LAeq,8 h
5 Pa2  =  91.9 LAeq,8 h
10 Pa2  =  94.8 LAeq,8 h

The Noise Dose examples above assume the UK and EU default criterion time of 8 hours and exchange rate of Q = 3

Related Terms - alphabetic listing

Estimated Noise Dose is the exposure received if the measured level had existed for the specified criterion time.

Noise Damage Risk Criteria is the recommended maximum noise levels for given exposure periods.

Noise Dose % is the noise exposure expressed as a percentage of the normal allowable daily 'noise dose' collected during measurements on a worker with a noise dosimeter. Noise Dose % varies according to National Standards and is sometimes referred to as the % noise dose

Noise Dose Badge, a small device worn by operator to store fluctuating noise levels during working day, similar to a noise dosimeter.

Noise Dose Criterion Level is the maximum Leq sound level allowed for an 8-hour period and corresponds to the 100% noise dose value. Also used for calculating the noise dose % and the ProjDose

Noise Dose Criterion Time is the time in hours used to calculate noise dose %, normally 8 hours.

Noise Dose per Hour (DOHR), shows the dose exposure over each hour.

Noise Dose Threshold Level, some regulations specify that for the measurement of noise at work, the noise levels below a certain limit (the threshold) should be disregarded. Some noise dose meters therefore only sum up the contributions from the levels above the threshold and uses these values to calculate the noise dose parameters.

Noise Dosimeter. a pocket sized instrument designed to be worn during all or part of the day as a personal noise monitor in order to check an operator's personal exposure to workplace noise.

Also known as a noise dosemeter and a sound exposure meter

Noise Exposure Time, the time a person is exposed to noise during a workday - used for calculation of LEP,d (daily personal noise exposure).

Personal Hearing Protectors

Projected Noise Dose (NProjDose), uses the current noise dose value, logged during the present measurement, and projected forward to give the predicted 8 hour period, assuming the noise levels for the remaining time stays the same.