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FAQs on Noise Protection

Definitions, Hazards & Selection

Q: What is the difference between earplugs and earmuffs? protectors” as used in the provision means protectors that are
A: Earplugs are simple to use, less expensive than muffs and comfortable to wear and that offer sufficient attenuation to
more comfortable in hot or damp work areas. Ear muffs are prevent hearing loss.
easier to fit, generally more durable than plugs and have -How to find out the attenuation As per OSHA 1910.95 app B
replaceable parts. In areas where noise levels are very high, For Single Protection
muffs and plugs can be worn together to give better When using a sound level meter set on the C-weighting network:
protection. A. Obtain a representative sample of the C-weighted sound levels
Q: Will the eardrums be poked out with earplugs? in the employee's environment.
A: That is unlikely for two reasons. First, the average ear canal is B. Subtract the NRR from the C-weighted average sound level to
about 1inch long. The typical ear plug is between 1/2 to 3/4 of obtain the estimated A-weighted TWA under the ear protector.
an inch long. So even if you insert the entire earplug, it would
still not touch the eardrum. Secondly, the path from the Estimated Exposure (dBA) = TWA (dBC) - NRR
opening of the ear canal to the eardrum is not straight. In fact,
it is quite irregular. This prevents you from poking objects into Single Protection Example:
the eardrum. 1. C-weighted TWA=108 dBC, ear plug NRR =32
Q: If earplug and earmuff are used together, will the NRR be 2. Estimated Exposure= 108 – 32 =76 dBA
total of both the equipments? This hearing protection is considered adequate, as it is below the
A: Earplugs worn in combination with earmuffs, helmets or 85 dBA threshold.
communications headsets, typically provide greater protection
than either device alone. However, the attenuation of the For dual protection (ear muffs and plugs are used
simultaneously) use the following:
combination is not equal to the sum of the individual A. Determine the laboratory-based NRR for the higher rated
attenuation values. protector (NRRh).
For example, at 1000 Hz the combination of a 19 dB plug and B. Add 5 dB to the field-adjusted NRR to account for the use of the
a 21 dB muff does not yield 40 dB overall, but rather about second hearing protector.
31dB. The simplified solution would be to add 10 dB over the C. Subtract the remainder from the TWA as follows:
highest device viz 21 dB+10 dB=31 dB. Estimated Exposure (dBA) = TWA (dBC) - (NRRh + 5)
Q: What is the unit measurement of noise?
A: It is calculated in Decibel (dB). For every 5 dB increase, the Dual Protection Example:
noise is louder by double. 1. TWA=110 dBC, plug NRR=29, and muff NRR=19 dB
2. Estimated Exposure = 110 - (29 +5) = 76 dBA
NRR – Noise Reduction Rating. It is a laboratory-derived numerical This hearing protection is considered adequate, as it is below the
estimate of the attenuation that is provided by the protector. 85 dBA threshold.
Note:
Attenuation - Attenuation refers to the damping or decrease of If A weighted TWA is set in the sound level meter then
noise levels as a result of wearing Hearing Protector Devices deduct value of 7 from NRR Hearing Protection.
(HPDs).
Suitable Hearing Protector - The term “suitable hearing
Acoustic Measuring System
EARMUFFS EARPLUGS
Headband

Ear cup Cushion

Sound damping material

Attached to a helmet

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