Industrial Paramedical Services hearing information services.
| See how hearing works by taking sound waves and
converting them into intelligible sounds. Click ear diagram image below to see the
complete visual story in large detail. 
| Case Study of Noise-Induced Hearing Loss. The audiogram below belongs to a man
whose hearing loss was caused by gunfire while serving in World War II. After the war, he
continued to be active in shooting sports. You can see that his hearing loss is most
pronounced in the areas critical to understanding speech. Symptoms of Hearing Loss:
- Hearing but not understanding
- Turning up the volume on the TV
- Must lip read to understand speech
- Cannot hear environmental sounds such as game calls, traps releasing, crickets, etc.
- Strained personal relationships, denial
- Social withdrawal
- Fatigue and stress
Keep in mind that conversational speech is approximately 60-65 dB, and the threshold of
pain is considered to be 140 dB. According to Dr. William Clark, Ph.D. senior research
scientist in charge of the NOISE LABORATORY at the Central Institute for the Deaf in St.
Louis, the damage caused by one shot from a .357 magnum pistol, which can expose a
shooter to 165 dB for 2msec, is equivalent to over 40 hours in a workplace with a 85dB
noise level.
Dr. Krammer continues to say that shotgun noise averaged slightly more
that 150dB. This is approximately 14dB beyond the threshold of pain, and more than
sufficient to cause sudden hearing loss with complications. Krammer adds that sound
pressure levels for the various pistols and ammunition tested yielded an average mean of
157.5 dB, which is greater than those previously shown for shotgun and rifle noise levels. |
| NOISE EXPOSURE
TIME LIMITATIONS |
| Noise Level |
Exposure Limits |
| 90 dB |
8 hrs |
| 95 dB |
4 hrs |
| 100 dB |
2 hours |
| 105 dB |
1 hour |
| 110 dB |
30 minutes |
| 115 dB |
15 minutes |
| GUNFIRE NOISE LEVELS |
| .38 Spl. |
156 dB |
| .44 Mag |
164 dB |
| ENVIRONMENTAL NOISE
LEVELS |
| 140 dB |
Space rocket at blastoff |
| 130 dB |
Jackhammer |
| 120 dB |
Ambulance siren
Amplified rock band
Thunder clap |
| 115 dB |
Sandblasting |
| 110 dB |
Woodworking shop |
| 100 dB |
Pneumatic drill
Chainsaw |
| 90 dB |
Lawn mower
Disco dance music
Shop tools
Truck traffic
Noisy restaurant |
| 80 dB |
City traffic
Loud music from radio |
| 75 dB |
Kitchen appliances |
| 70 dB |
Crowded restaurant |
| 65 dB |
Conversation speech |
| 60 dB |
Sewing machine
Typewriter |
| 50 dB |
Average home interior |
| 40 dB |
Quiet residential community |
| 30 dB |
Whisper at five feet |
| 20 dB |
Leaves rustling in a breeze |
| 10 dB |
Normal breathing |
| 0 dB |
Faintest sound heard by a human ear |
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| OSHA’s Hearing Conservation
Requirements Whenever
feasible, employers are required to reduce the noise at the source through engineering
solutions. When this is not possible or economically feasible, it is acceptable to use
hearing protection as a temporary solution. The term hearing conservation as defined by
OSHA includes the following aspects, which the employer is responsible to carry out:
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Monitoring of the noise environment. If
the TWA (Time Weighted Average) noise level is exceeding 85 dB(A), a hearing conservation
program is required. |
|
Selecting hearing protection devices
appropriate for the environment or environments at hand. Several different types of
hearing protectors are required to be offered to the employees, in order to introduce a
level of personal choice. The employer is responsible to pay for the original equipment as
well as replacements. The employees are required to use the hearing protection, and the
employer is responsible for the enforcement. |
|
Training and educating employees in the
proper use of hearing protection, the importance of full time use of hearing protectors
when working in a noisy environment. Education and training is considered an essential and
ongoing activity. |
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Establishing a baseline audiogram for each
noise exposed employee, and annual hearing tests thereafter in order to monitor the
effectiveness of the hearing conservation program. |
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Take corrective action when it is
concluded that noise induced hearing damage is occurring. Corrective action can entail
further education and training in the use and importance of full time use of hearing
protection. Using hearing protectors better suited to the environment and the
individual. Using administrative controls, which simply means to reduce the exposure time
for the employee in question. If these efforts fail, an employee may be transferred to a
quieter job. |
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The above summary of OSHA’s hearing
conservation requirements is not intended to be complete. The complete regulation (29CFR-1910.95) is available on the internet. |
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OSHA’s Permissible Noise
Exposure
- 90 dB
- 92 dB
- 95 dB
- 97 dB
- 100 dB
- 102 dB
- 105 dB
- 110 dB
- 115 dB
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- 8.0 hours
- 6.0 hours
- 4.0 hours
- 3.0 hours
- 2.0 hours
- 1.5 hours
- 1.0 hours
- 30 minutes
- 15 minutes
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- How to use the NRR
When the dB(C) noise level is known, you don‘t have to adjust the
NRR:
Noise level at ear: dB(C) - NRR =< 90 dB (*)
When the noise level is known in dB(A) the NRR must be reduced by 7 dB:
Noise level at ear: dB(A) - [NRR –7] =< 90 dB (*)
(*) If a threshold shift (hearing damage) exists the noise level at the ear must be 85
dB or less.
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- Overprotection can be a problem!
Selecting a high NRR hearing protector for an environment where only good
high frequency attenuation is needed, will lead to unnecessary insulation and
communications difficulties.
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- Field Attenuation It has been
proven in many studies that hearing protectors are not as effective in the field, as the
laboratory numbers indicate. In the laboratory the hearing protectors are used correctly,
while in many field situations they are not. Employees are either not trained or motivated
to make the effort to use the protectors in a correct way. NIOSH recommends a de-rating of
50-70% for earplugs and 25% for earmuffs.
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- Is Your Program Working? How
do you know if your hearing conservation program is working? The answer is in your annual
audiograms. If they do not show any new noise induced hearing damage, your program is
working.
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What is Tinnitus?
Tinnitus is a ringing, buzzing, hissing or other head noise that does not come from
an external source.
What is the cause of tinnitus?
One of the most common causes is exposure to loud noise.
Workplace noise can cause hearing loss and tinnitus. If those exposed to loud sound do not
wear proper hearing protection devices, they may find they gradually lose their hearing
and suffer from tinnitus. Excessively loud sound can also be from music, power tools and
chain saws, gunfire, explosives, and motorcycles.
Tinnitus may only be an annoyance for some people; however, for
others it is a chronic condition, which can cause sleeplessness and lack of concentration.
This can be a serious problem that can be avoided by proper precaution.
A person who tells a physician about tinnitus may be told to
“Go home and live with it.” This is possible for some, but others need
treatment. Feeling there is no cure for tinnitus can turn a benign symptom into a feeling
of helplessness and despair. Negative counseling which provides no hope can actually
increase the patient’s perception of tinnitus as he feels it will go on forever, may
get worse and cannot be effectively treated.
There is help! There is a national organization dedicated to
silencing tinnitus. Any person suffering from tinnitus should con tact the American
Tinnitus Association (ATA) at 1-800-634-8978. They will be told about tinnitus clinics
throughout the United States that work with patients in alleviating tinnitus. Self-help
groups sponsored by the ATA provide information and support. American Tinnitus Association
has their materials available for the worker who says that tinnitus is causing distress,
sleeplessness and affecting his or her work. Provide the employee with ATA’ s website
information, http://www.ata.org.
The information on this site is reliable so the individual is not reading anecdotal
information from unknown sources.
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