Question

An employer needs to reduce noise exposure so that an employee can work on a machine generating 117 dBA for 1 hour. What noise reduction rating should the employer seek to stay within allowable limits and have a 50% safety factor?

FA = field attenuation (approximate) in dBA

NRR = noise reduction ration in dBA

FA= (NRR-7)/2

Answer 1

Given sound level : 117dbA for 1 hour

We need to calculate the NRR (Noise reduction rating) that will make employer's ear safe and have 50% safety factor.
The 50% safety factor for 1 hour of noise, leads to the sound level of 90dBA

(The difference between dB and dBA is, dB = sound pressure level, dBA = sound pressure level weighted curves for human ears, to dBA plays more significant role than dB in case of noise reduction).

So, the noise should be less than or equal to 90dBA, thus, we need to reduce (117-90 = 27 dBA)

using formula:

Noise Reduction Rating rating should the employer seek to stay within allowable limits and have a 50% safety factor = 61.

Upvote, if the answer was helpful. Have a nice safe day.