Casella CEL-35X dBadge Users Handbook – Page 39
Where PNR is the predicted noise level reduction provided by the
hearing protection. For example, if from the CEL-352 dBadge
‘Plus’ the values were:
L
Ceq
102.4dB L
Aeq
98.6dB
Therefore, as the L
Ceq
– L
Aeq
value is greater than 2:
PNR = M – x (L
Ceq
– L
Aeq
– 2)
From the example of the hearing protector mentioned above:
PNR = 25 – x (102.4
– 98.6
– 2)
PNR = 25 – 1 x 1.8
PNR = 25 – 1.8
PNR = 23.2dB
The A-weighted SPL at the ear = L
Aeq
– PNR
The A-weighted SPL at the ear = 98.6 – 23.2 = 75.4 = 75dB(A)*
*Note: some countries assume that ‘real world factors’ will
effectively reduce the effectiveness of hearing protection. For
example, in the UK a further standard 4dB is taken off the PNR, so
in this case the value at the ear would be 79dB(A).
(25-17)
8
(M-L)
8
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