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Noise & Your Ears

Noise is unwanted sound. Loud noise can damage your ears. Unfortunately, many believe that they can “get used to” loud noise, or can recognize the signs of damage before it becomes a problem. Noise can affect your ears in two ways. It can produce:

  • hearing loss by damaging the structures inside your ear
  • tinnitus continuous or intermittent ringing or noise heard inside the head.

Hearing loss can affect all areas of your life. Both hearing loss and tinnitus can cause irritability, fatigue, high blood pressure, and stress. At work, it can impair your ability to detect warning signals, hear clearly in meetings, and listen on the telephone. Noise-induced hearing loss normally takes place gradually, with no external signs of damage, and often without warning symptoms or pain. Fortunately, this type of hearing loss is preventable. The use of hearing protection will not bring back lost hearing, but it can stop further damage from occurring.

Decibel Level (dBA) Source
   
0 acute threshold of hearing - weakest sound
15 threshold of hearing
30 a whisper
45 rustling leaves, soft music
60 normal conversation
75 average radio or vacuum cleaner
*82 a very noisy restaurant, ACTION LIMIT
90 lawnmower, Sawzall
100 tractor, leaf blower, power saw
120 chain saw, jack hammer, rock concert
135 jet take-off, amplified music
140 gunshot, siren at 100 feet; threshold of pain
   
Note: Decibel = measure of loudness, more specifically pressure. The "A" scale is noise within human hearing range.

* Levels above 82 dBA require hearing protection.
The damage caused by noise can be temporary or permanent. Temporary hearing loss is hard to detect unless you have a hearing test performed. Most people don’t notice hearing loss until it becomes permanent. For example, you might notice that you can not hear consonant sounds, you might find it harder to hear the higher-pitched voices of women and children, or voices may seem muffled. As a participant in the Reed College Hearing Loss Prevention Program (HLPP), you will learn how to choose the proper hearing protection and how to limit your exposure to loud noises. You will also receive annual hearing tests to help track hearing loss and the program’s effectiveness.

In some circumstances, the Environmental Health and Safety (EHS) office will provide dosimetry. Dosimetry is sound monitoring that can give a more accurate picture of total noise exposures for a typical work shift.

Noise & Hearing Protection

Most people can be exposed safely to a sound source producing 82 dBA for a maximum of eight hours (Refer to the chart below for specific exposure limits). You should never directly expose your ears to sounds greater than 115 dBA.

For every 3 dB increase above 82 dBA, the permissible exposure time is reduced by half.

  • Example 1- If you used a lawnmower with an 85 dBA rating, you risk hearing loss after four hours of exposure. If the lawnmower had an 82 dBA rating, you could use the lawnmower for eight hours before reaching the same risk level.
  • Example 2- With a tool that produces a noise level of 88 dBA, you could work for a maximum of two hours per day. In this case you would arrange work schedules to allow you to rotate work activities at least every two hours so that no one person is exposed to a dangerous amount of noise. If, however, you use the appropriate hearing protection, you could bring your exposure level down below 82 dB for a full 8 hours of allowable exposure time.

The attached table only takes temporary hearing loss into consideration. Ears need a recovery period after being exposed to noise. If you were exposed to a noise level of 88 dBA for 2 hours, for example, the remaining 22 hours of that day's exposure should be at a noise level below 82 dBA. This allows the ear to recover from potential temporary hearing loss. This recovery period varies, depending upon the individual, the severity, and the length of exposure. Hearing usually returns almost completely in 12 to 14 hours provided there is no more noise exposure exceeding 82 dBA. Any hearing that does not return becomes permanent hearing loss. With repeated exposure, hearing loss worsens.

Types of Hearing Protection

Noise-induced hearing loss is irreversible. In order to ensure hearing preservation, you should use hearing protection during any activity that exposes you to noise above 82 decibels averaged over an 8-hour day (See first chart for some examples). The EHS office can provide you with a chart of the noise levels for machines in your department. Make sure the hearing protection you use is sufficient for the noise exposure.

Minimum Required Levels Of Protection For Various Noise Levels:
82 dBA or below voluntary
83 - 88 dBA HPD requiredNRR19 or above
89 - 94 dBA
HPD required NRR29 or above
95 - 96 dBA HPD required NRR33
97 -101 dBA
HPD required NRR33 earplugs with earmuffs
> 101 dBA Consult with the EHS Office
There are several types of hearing protection aids that offer varying levels of noise reduction depending on your needs. The amount of noise reduction, or protection factor, is measured as a Noise Reduction Rating (NRR). The higher the number the more protection it provides. Be aware of the difference between the rating of hearing protection and the actual protection it affords. To calculate the actual protection: take the rating, subtract 7, then divide by 2. For example, an earmuff rated at 31 actually provides 12 dB of protection [31 – 7 = 24; then 24 ∏ 2 = 12].

Earmuffs: Earmuffs are the easiest form of hearing protection to remove and put back on. They resemble stereo headphones. The soft plastic cushions, filled with foam or liquid, should form a good seal to your head to exclude noise. If you wear glasses with wide temples, you may want to choose another type of protector. Wipe the cushions clean with a damp rag when they become soiled. Check the cushions often, and replace them if they become stiff, worn, cut, or torn. Do not modify your muffs in any way. The highest protection factor in earmuffs that are readily available is NRR31. Use good quality muffs purchased from a reputable company. Examine them for comfort, construction, seal, and NRR. Contact the EHS office for information on where to purchase quality hearing protection devices.

Disposable Earplugs: Disposable plugs are commonly made of expandable foam and fit snugly inside the ear canal. Your ear canals as well as earplugs can differ in size. Find one that fits comfortably for you. Once inside your ear canal, earplugs expand to form a good seal. The highest protection factor available is NRR33. Always inspect them before reinsertion. Throw away damaged or dirty earplugs.

Disposable Earplug Fitting Instructions

To Avoid Hearing Damage, Plan Your Day!

When in a high noise environment,

  • Arrange to rotate job duties with coworkers before reaching the exposure limit.
  • Use hearing protection.
  • Remember to protect your ears while you’re off the job. Loud music, lawnmowers, motorcycles, chain saws, jet skis, and many other devices can damage your hearing.

This can help to eliminate individual over-exposure. Use the attached table to determine noise exposure limits. Never exceed these limits.

Step 1: Before fitting any earplugs, make sure your hands are clean. Hold the earplug between your thumb and forefinger. Roll and compress the entire earplug to a small, creaseless cylinder. Straighten your ear canal by using your other hand to reach over your head and pull up and back on your outer ear.

Step 2: Insert the earplug and hold for 20 to 30 seconds so the earplug can expand and fill your ear canal.

Step 3: Test the fit. In a noisy environment, and with earplugs inserted, cup both hands over your ears and release. You should not notice a significant difference in the noise level. If the noise seems to lessen when you cup your hands over your ears, your earplugs are probably not fitted properly. Remove and refit following instructions. Check periodically to be sure that the fit is still snug.

Step 4: Always remove earplugs slowly, twisting them to break the seal. If you remove them too quickly, it could cause pain and damage your eardrum.

Reusable Earplugs: Reusable plugs are preformed to fit the ear. Usually made of a flexible rubber or silicon, they may be flanged or cone-shaped. Some come joined by a cord so that they're not easily lost. You can wear reusable plugs safely for 1 to 6 months, or more depending on the type. Replaced them if they become hard, torn, or deformed. Inspect and clean them often with warm soapy water. Rinse well. Store the dry plugs in the case supplied.

Combination Use of Earplugs and Earmuffs: The combination of earmuff & earplug use will give you more protection than either one alone. Any secondary form of ear protection will add 5 dBA to the total. To calculate, use the higher-rated protective device as the base, and add 5 for the other form. For example, use of NRR33 earplugs and NRR 29 earmuffs will bring your total protection to 18 dBA (33-7=26; 26∏2=13 13+5=18). You can use combination protection for noise levels up to 101dBA.

 

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