Importance of Hearing Protection

Hearing loss is a function of exposure time, the average sound level, and the peak level of very loud sounds. Exposure to excessive noise from industrial machinery, heavy construction equipment and vehicles, power tools, aircraft, gunfire, motorcycle and auto race tracks, dental drills, sporting events, fireworks, rock concerts, marching bands, and music from a player's own instrument or nearby instruments can cause hearing loss depending on the intensity and duration of the noise. Some persons are more susceptible to hearing loss from high-level sound than others.

Some workers obviously need high-attenuation earplugs. Shipbuilders, flight crew who stand behind jet aircraft on the flight deck, and army tank operators usually fall in this category. Such individuals can't get enough attenuation for proper protection even with plugs and earmuffs combined. But, many industrial workers can be adequately protected with as little as 10 dB of attenuation: the majority of eight-hour equivalent noise exposures fall between 85 and 95 dB. Some of these workers receive earplugs that provide too much attenuation, and as a result they do not insert them deeply in their ears because they can not hear speech clearly enough. These persons risk hearing damage, but have compromised so they have auditory awareness of sounds around them.

The cochlea has two types of hair cells, inner and outer. The outer hair cells appear to provide the ear's sensitivity to hear quiet sounds. Inner hair cells appear to provide all the information to the brain. It has been suggested that high-intensity noise causes extensive damage to the inner and outer hair cells; long-term lower-level noise causing the same audiometric loss may show predominately outer hair cell loss. What this implies is that the type of noise exposure may determine the severity of future communication problems.

Tinnitus (ringing in the ears) and temporary hearing loss can occur from a single concert, sporting event or sudden loud noise like a firecracker. In rare cases, permanent hearing loss results from such auditory insults. Even if a temporary hearing loss recovers over a period of hours to days, there is a risk that repeated exposure to loud noise will result in permanent hearing loss.

It is important that hearing protection is carefully selected for each individual, based on the intensity level, duration, and type of noise exposure.

Allowable Weekly Sound Exposure To Be Safe

Recommended Maximum Weekly Exposure (NIOSH, 1998)

Sound level (dB) Exposure type No protection Using ER•20s
60 Conversation SAFE -
80-85

Noisy restaurant
Vacuum cleaner
Average factory

40 HRS. SAFE
88 Circular saw
Loud party
Motorcycle
20 HRS. SAFE
94 Subway
Riding mower
5 HRS. SAFE
97 Live band 2.5 HRS. 40+ HRS.
100 Sporting event
Chain saw
Snowmobile
1.25 HRS. 40+ HRS.
112 Blues bar/Rock concert 5 MINS. 8 HRS.
115 Ambulance siren 2.5 MINS. 4 HRS.
Above 125 dB you are at risk for any period without maximum protection
140 Jet engine
Gun shot
Firecracker
INSTANT LOSS  

Allowable Daily Exposure (OSHA and NIOSH)

source level in dB 85 88 90 92 94 95 97 100 105 110 115 120
OSHA 16   8 6   4 3 2 1 1/2 1/4 1/8
NIOSH 8 4     1 3/4 1/2 1/4        

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.

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