1. Occupational Noise Exposure
Hearing Conservation Training Program

2. آسیب های صوتی شنوایی

3. چه مدت میتوان در صداهای شدید حضور داشت
90 dbA
8 hrs
92 dbA
6 hrs
95 dbA
4 hrs
97 dbA
3 hrs
100 dbA
2 hrs
102 dbA
1.5 hrs
105 dbA
1 hr
110 dbA
0.5 hr
115 dbA
0.25 hr or less

4. 60 dB
صحبت روزانه و زنگ تلفن
70 dB
رستوران
80 dB
ترافیک شهری, صدا در کارخانه , vacuum cleaner.
90 dB
Subway trains, موتورسیکلت, workshop tools, lawn mower. 8 hrs
100 dB
اره برقی, pneumatic drill. 2 hrs
110 dB
مجالس عروسی ها ارکستری. 30 minutes
120 dB
Rock concert speaker sound, sandblasting, 15 minutes or less
130 dB
تیک آف هواپیما.
140 dB
شلیک گلوله Nerve damage occurs immediately
150 dB
rock music peak

5. Lawn mower
Sandblasting
Pneumatic drill

6. Did You Know?
About 30 million workers are exposed to hazardous noise on the job
Noise-induced hearing loss is the most common occupational hazard for American workers
Hearing loss from noise is slow and painless; you can have a disability before you notice it
If you must raise your voice to speak with someone only 3 feet away, you are in high (hazardous) noise.
It is 100% preventable

7. What Is Noise? Noise is any unwanted sound
By-product of many industrial processes, e.g. operating machinery
Exposure to high levels of noise may lead to hearing loss and other harmful health effects

8. Common Sounds may be louder than you think…

9. Signs of Hearing Loss
Do you ask people to speak louder so that you can hear?
Do you have to turn the TV or
Radio so loud that others
complain?

10. Temporary Hearing Loss Permanent Hearing Loss
- results from short term exposure to noise
- hearing returns when away from the noise
Permanent Hearing Loss
- results from exposure to a moderate or high level of noise over a long period of time
-hearing loss is PERMANENT
Noise induced hearing loss is a gradual loss of hearing sensitivity due to years of exposure to harmful noise.

11. Threshold Shifts Temporary Threshold Shifts (TTS)
Hearing returns to normal after noise exposure
Permanent Threshold Shifts (PTS)
Repeated noise exposure without a return
to normal 11

12. Non-Auditory Effects of Noise
Effects cardiovascular system
Effects the nervous system
Interferes with speech and concentration
Causes annoyance, stress, and fatigue
Reduces work efficiency
Lowers morale
Masks warning sounds
Illustration: Microsoft Clip Art 12

13. Effects of noise to inner ear
Hair cells in inner ear transmit noise signals to the brain
“ These are photos greatly magnified showing the hair cells in the inner ear. The photo on the right shows hairs on top completely destroyed by exposure to excessive noise. Usually the hair cells that detect higher pitches are damaged or destroyed first.”
Normal hair cells
Noise-damaged hair cells 5

14. Tinnitus From Noise Exposure
Exposure to high noise levels can also cause permanent ringing in the ear or “tinnitus”.
Tinnitus sufferers usually complain of constant whistling, squealing, roaring or buzzing in one or both ears.
Severe tinnitus may disrupt sleep, reduce concentration and cause irritability and depression.
“Tinnitus is difficult to treat. Many doctors will tell a person with tinnitus that “they just have to live with it” . There are several treatments that can provide some relief however, including certain drugs, masking devices worn in the ears, or other devices which help the brain ignore the sound. [More information on treatment on tinnitus can be obtained from the American Tinnitus Association in Portland, Oregon. Their phone number is or ] 7

15. Selection of Hearing Protection Devices
Hearing protection devices are selected according to:
Employee comfort
Level of noise exposure
Type of work being performed
Environmental conditions
Employee may select hearing protection from a variety of suitable
hearing protectors provided by employer.
NRR – Noise Reduction Rating
The purpose of the NRR is to give an indication of the amount of noise reduction that may be expected with a specific hearing protection device.
This number is to be used as a general guide only! The true amount of noise reduction depends on how the employee inserts the hearing protector into the ear.

16. Types of Hearing Protection Devices
Ear muffs
Foam insert earplugs
Semi-aural earplugs

18. Ear Muffs Disadvantages Advantages Higher cost
More protection at higher frequencies than earplugs
Durable, long lasting
Can be fitted on hard hat
Reusable
Disadvantages
Higher cost
Eye glasses can interfere with ear muff seal
May be uncomfortable in hot environments
Must be cleaned before use by another worker

19. Foam Insert Earplugs Disadvantages Advantages
More protection at lower frequencies than muffs
Inexpensive; disposable
Can be custom molded for individual worker
Reusable plugs are available
Disadvantages
Hands must be cleaned before inserting earplugs
Improper insertion reduces value

20. Semi-aural Caps Advantages Easy to insert May be used several times
Ideal for people going in and out of noisy areas
Disadvantages
Improper insertion reduces effectiveness
More expensive than ear plugs
Typically have lower than plugs or muffs

21. Fit, Use, and Care of Hearing Protection Devices
Employer must ensure proper initial fitting
Employer must supervise the correct use of hearing protectors
Hearing protectors must be replaced as necessary at no cost to employee, contact your supervisor
Hearing protection devices must be cleaned and stored according to the manufacturer’s specification\
Hearing protection devices can be cleaned with soap and warm water. Make sure that they are completely dry before putting them in your ears.

22. Audiometric Testing Monitors employee’s hearing over time
Baseline audiogram must be performed within first 6 months of work exposure ( 8 hour TWA ≥ 85 dBA)
Annual audiograms are required each year after baseline audiogram
Employer must pay for the cost of each required audiogram

23. Why Do Audiometric Testing?
Obtain a Baseline Audiogram for future comparison
Identify occupational hearing loss
Identify Standard Threshold Shifts (STS)
Standard Threshold Shift – a change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more.

24. Example of Audiogram
Chart: NCDOL-OSH Division

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