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Therefore as (LCeq – LAeq) = 0.2
PNR
19
25 19
−
4
103.4 103.2
−
2
−
(
)
⋅
−
:=
PNR = 21.7 dB
To find the A-weighted level at the ear subtract the PNR from LAeq: -
A-weighted level at ear = LAeq - PNR
A-weighted level at ear = 103.2 – 21.7 = 82 dBA
4dB Correction applied = 86dBA
In accordance with the Control of Noise at Work Regulations 2005, the
predicted level of noise with hearing protection must be increased by 4dB,
therefore the quotable predicted noise level taking into account the worn
hearing protection is 86dBA.
Protection Calculation – SNR Method
This is the easiest but generally the least accurate method for calculating
hearing protection.
Simply measure the C-weighted energy equivalent sound level.
LCeq = 101.0 dBC
Take the manufacturers ear protector data: -
SNR = 28 dB
To find the C-weighted level at the ear subtract the SNR from LCeq: -
C-weighted level at ear = LCeq - SNR
C-weighted level at ear = 101.0 – 28 = 73 dBC
4dB Correction applied = 77dBC
Note: As the SNR method requires C-weighted Leq (LCeq) and A-weighted Leq
(LAeq) is a requirement of risk assesments then the HML method should be
used in preference to the SNR method.
Leq
See ‘Energy Equivalent Sound Level’.
Minimum rms Level (L
min
)
This is the lowest root-mean-square sound pressure level measured over the
measurement time period.
