HEARING PROTECTION DEVICES

Approved Types of HPD’s: Earplugs .Pre-formed Single Flange Triple Flange Quad Flange Combat Arms Ear Plugs .Hand-formed Noise Muffs Ear Canal Caps Helmets

Pre-Formed (Vinyl) Earplugs Single Flange (No longer manufactured): Noise Reduction Rating (NRR)=23dB 5 color-coded sizes: White (Extra Small) Green (Small) Orange (Medium) Blue (Large) Red (Extra Large)

Pre-Formed Earplugs (cont.): Triple Flange: NRR= 26dB 3 color coded sizes: Green (Small) Orange (Medium) Blue (Large)

Pre-Formed Earplugs (cont.): Quad Flange: NRR= 25dB

NRR=19-28dB, depending on fit characteristics. Hand Formed Foam Earplugs NRR=19-28dB, depending on fit characteristics.

Ear Canal Caps: Noise Reduction Rating (NRR)=18dB NRR is extremely variable with this HPD

Noise Reduction Rating (NRR)=25dB Circumaural Noise Muffs Noise Reduction Rating (NRR)=25dB

HPD Selection Considerations: Only approved protection is acceptable Selection should be based on Advantages/disadvantages Work environment Attenuation NRR

NRR ?

The NRR describes: the average sound level reduction (attenuation) provided by a hearing protection device (HPD) in a laboratory test.

Manufacturers of HPDs are required by the Environmental Protection Agency to have various products tested in order to obtain an NRR prior to placing them on the market.

Actual noise reduction achieved under field conditions using any HPD will be much lower than the assigned NRR.

Adjustment of the assigned NRR may need to be made before a device is prescribed for field use.

A. WEIGHTING-SCALE ADJUSTMENT .If workplace noise levels are determined by using the A scale (dBA) on the monitoring instrumentation, the assigned NRR must be reduced by 7 dB before being subtracted from the actual measured TWA noise levels to determine the legal "adequacy" of the device

B. DERATING OSHA derates NRR (after weighting-scale adjustment) by one-half (50%) for all types of HPDs to determine the "relative performance."

B. DERATING ( cont.) NIOSH recommends a variable scheme for derating For example, Earmuffs are derated 25% formable earplugs are derated 50% all other earplugs are derated 70%

THESE RESULT IN: “Predicted field attenuation” or “relative performance” of the device.

C. COMBINING HPDS - The NRRs of the combined devices are not added together to determine the total noise reduction. - OSHA advises that 5 dB is to be added after thweighting- scale adjustment is applied to the device with the higher NRR (but does not require the 50% derating described earlier).

As a practical matter, Double protection is inadequate When TWA noise exposures exceed 105 dBA.

An Example of Reducing the NRR 8-hour TWA noise exposure: 93 dBA NRR of hearing protectors: 29 dB

1. Subtract 7 dB from the NRR: 29 dB - 7 dB = 22 dB 2 1.Subtract 7 dB from the NRR: 29 dB - 7 dB = 22 dB 2.Divide by 2: 22 ÷ 2 = 11 dB 3.Subtract 11 dB from the 8-hour TWA noise exposure: 93 dB - 11 dB = 82 dB 4.Decide if 82 dB ( “Protected Exposure”) is below the PEL for noise