Etymotic Research er-4b Broschüre

61 Martin Lane, Elk Grove Village, IL 60007   
847-228-0006

Conventional earplugs attenuate more in the high frequencies than in the low and mid frequencies, which makes

music and voices unclear and unnatural. Deeply inserted foam earplugs can provide 30-40 dB of attenuation, although
typically only a small amount of sound reduction is needed.

Noise-induced hearing loss is a function of exposure time, the average sound level and the peak level of very loud

sounds. OSHA set industrial limits of 8 hours per day at 90 dBA. NIOSH recommends a maximum allowable exposure of
40 hours per week at 85 dBA.

1) Earmold impressions that are not long enough (past the second bend)
2) Earmolds received from the earmold lab that are not long enough 

Deep earmold impressions (past the second bend of the ear canal) are required because earmolds that do not seal

deeply in the bony portion of the ear canal can create the occlusion effect. A shallow earmold can increase the occlusion
effect by as much as 15-20 dB at low frequencies. Silicone impression material is recommended. Vented otoblocks
decrease the likelihood of discomfort or damage to the ear during removal of deep 
impressions. If a remake is necessary because of the occlusion effect, it may be 
helpful for the person to vocalize “oo” or “ee” while the impression is setting.
Open-jaw impressions are also an option.

Etymotic Research produces a hand-held Occlusion Effect Meter which quickly 

quantifies the occlustion effect and earmold leakage. This information can reduce the 
need for remakes.

The EPA requires manufacturers to print a noise reduction rating (NRR) on all non-custom earplugs. The NRR 

for ER-20s is 12 dB, but actual clinical measurements of properly inserted ER-20s indicate that these earplugs 
provide almost equal sound reduction (20 dB) at all frequencies. The required formula used to determine NRR 
includes an adjustment for individual variability and for those persons who do not wear ear protection as instructed.
Many investigators have found no consistent rank order correlation between the real-world NRRs and labeled NRRs.
NRR is computed from laboratory data that are not representative of the values attained in the real world by actual users.

OSHA and NIOSH values listed above are given 
in daily exposure limits. According to the OSHA
standard, a person can be exposed to a 95 dB 
environment for 4 hours before risking hearing
damage. With 10 dB of protection that person 
can be exposed to 95 dB for 16 hours per day.
NIOSH values are more conservative.
For maximum protection, foam earplugs, muffs or 
other hearing protection devices are recommended.