5958_MCA Noise v2_4.indd - Institute of Sound and Vibration ...

Code of Practice for Controlling Risks due to Noise on Ships
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Absorption coefficient
The proportion of incident sound energy that is absorbed by a surface or
a material.
Action Values and Limit Values
The 2007 Noise Regulations list Lower and Upper Exposure Action Values
and Exposure Limit Values. These values are given as Daily Personal Noise
Exposure L EP,d or Weekly Personal Noise Exposure L EP,w ; these exposures
are measured in A‑weighted Sound Level L Aeq . There is also a C‑weighted
instantaneous peak sound pressure level L Cpeak . If these levels are reached,
various actions are to be taken by employer and employee.
The Lower Exposure Action Values are:
80 dB(A) L EP,d or 80 dB(A) L EP,w i.e. a personal noise exposure of
80 dB(A measured on a daily or weekly basis, or
135 dB(C) L Cpeak i.e. a peak sound pressure level of 135 dB(C).
The Upper Exposure Action Values are:
85 dB(A) L EP,d or 85 dB(A) L EP,w , or
137 dB(C) L Cpeak .
The Exposure Limit Values are:
87 dB(A) L EP,d or 87 dB(A) L EP,w , or
140 dB(C) L Cpeak .
Neither limit value may be exceeded.
Ambient noise
The background noise or prevailing general noise in an area or compartment.
Assumed protection
Of a personal hearing protector, at a specified frequency. In British practice,
the mean attenuation minus the standard deviation for a typical group of
wearers, as determined by a standard procedure. In reality, an optimistic
estimate of protection.
5958_MCA Noise v2_4.indd 54 26/2/10 10:02:12