The LEP,d is the level of personal noise exposure that a worker is exposed to in a day, normalised to an 8-hour work period. The letters in the term LEP,d refer to level, exposure, personal and daily respectively. If a worker’s shift is shorter or longer than 8 hours, the calculation of the LEP,d takes the shift length into account and gives the average sound level for an equivalent 8 hour shift. This means that a worker’s LEP,d can be easily compared to the exposure limits set out by the Control of Noise at Work Regulations, which specify exposure limits for an 8-hour period.
The dose is the noise exposure expressed as a percentage of the total allowable daily noise exposure.
SNR stands for single number rating. It is a single number, given in decibels, that allows a comparison of the attenuation provided by different hearing protectors. The noise level that reaches a user’s ear can be estimated by subtracting the SNR from the external noise level (in dB(A)).
A-weighted decibels, dB(A), are the units of sound exposure limits as specified by the Control of Noise at Work Regulations. Mandatory hearing protection zones are defined by areas where the sound pressure level reaches a daily or weakly average value of 85 dB(A).
C-weighted decibels, dB(C), are a unit of sound exposure. Whereas as the A-weighted decibels, dB(A), are used for general purpose noise measurements, the C-weighted decibel measurements are more closely correlated to way that humans perceive loud sounds.
The LAeq is effectively the average sound level over a given period of time. It has units of A-weighted decibels, dB(A).