2. HEARING PROTECTION DEVICES

3. 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

4. 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)

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

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

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

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

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

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

11. NRR ?

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

13. 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.

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

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

17. 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

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

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

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

21. 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).

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

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

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