Purdue University
Cooperative Extension Service
West Lafayette, IN 47907

Protect Your Hearing

F. R. Willsey
Professor Emeritus of Agricultural Engineering

Most people think of farming as the quiet life, far removed from the hustle of urban living and industrial noise. However, farms have some severe noise hazards which can impair hearing ability. Many farmers and farm workers have suffered some hearing damage. It is important to protect yourself from such damage.

Why We Lose Hearing

Permanent hearing loss may occur as a result of aging, disease, injury, or exposure to loud noises over an extended period. Due to the nature of farm work, loud, continuous noise has permanently damaged the hearing of some farmers.

To better understand sound induced hearing loss, take a look at the ear. The outer ear funnels sound waves to the eardrum, which vibrates in response. These vibrations are transmitted to the bones of the middle ear which pass them on to the cochlea or inner ear. In the inner ear, vibrations are picked up by thousands of tiny hairlike protrusions which send impulses to the brain. When the hairs of the cochlea have been stressed too hard for too long, they get fatigued and no longer respond to the sound. Rest away from noise will often restore them to normal. However, after much exposure to loud continuous sounds, some of the hairs refuse to straighten up, and this results in permanent hearing loss.

Usually, you won't be aware of the loss, since damage from continuous noise occurs gradually, and early losses occur in the higher frequency range and do not interfere with normal conversation. However, if nothing is done to reduce your exposure to noise, your hearing ability will continue to drop until your ability to hear and understand speech is affected. By the time you notice it, serious damage has already taken place.

How can you tell if you have hearing damage? Look for these early symptoms . . . Do you find it difficult to carry on a conversation in a noisy situation? Do your ears ring or do you hear head noises for a time after you have been exposed to noise?

It is best to get a complete hearing test by a competent specialist. If this is done annually, damage can usually be detected before serious hearing loss occurs.

Sound Measurement--The Decibel

To understand sound levels, you need to understand the units that sound is measured in.

The decibel (dB) is the standard method of expressing sound intensity. An increase of just a few dB represents a considerable increase in sound intensity and can make the difference between safe noise levels and those which can damage hearing.

TABLE 1. Decibel Levels of Common Sounds at Typical Distance from Source

  0    Acute threshold of hearing
 15    Average threshold of hearing
 20    Whisper
 30    Leaves rustling, very soft music
 40    Average residence
 60    Normal speech
 70    Noisy office or work area
 80    Window air conditioner, heavy
 85    Inside  acoustically  insulated
        protective tractor cab in field
 90    OSHA limit--hearing damage
        on excess exposure to noise
        above 90 dB for eight hours per
100    Noisy tractor, power mower
120    Jackhammer, thunderclap,
        amplified rock music, gun blast

Safe Noise Levels

Permissible noise exposures for industry are incorporated in the standards of the Occupational Safety and Health Act. These limits should be a guide for all farm and ranch workers to avoid harmful noise exposure.

  Maximum safe
  Duration Per
    Day-Hr.     Sound Level - dB*
       8                90
       4                95
       2               100
       1               105
     1/2               110
 1/4 or less           115
*  As measured on standard sound level
meter, A scale, slow response.

How to Control Noise and Protect Yourself

Solution to a noise problem involves 1) the source of sound, 2) the path along which sound travels, and 3) the ear.

You can control noise at the source by keeping the engine exhaust system in good repair and using good quality mufflers on every machine. "Straight pipes" increase the noise problem greatly while making little or no difference in horsepower.

Properly maintained and lubricated machinery helps to reduce noise.

Tractor cabs are one method of noise control used to block the path of the noise. However, many older model cabs not designed to reduce sound are often a greater noise hazard than no cab at all. The user might consider installing noise barriers, acoustical materials, etc., to make a cab quieter. First, learn how to do the job correctly. It isn't easy to change a noisy cab to a quiet one.

When buying a tractor with cab or just a cab, select one designed for noise control. The Nebraska Tractor Tests now include noise ratings.

Reduce Noise by Protectors

An effective and simple way of safe-guarding against noise-induced hearing loss is by using hearing protectors. The two basic types of hearing protectors are ear plugs and ear muffs.

Preformed ear plugs made of plastic or rubber, are inexpensive, but should be fitted by a physician to get a good seal, since some people need a different size for each ear. These plugs tend to work loose with jaw movement so they should be re-sealed from time to time. They must be kept clean to prevent ear infection. However, they are lightweight, easily carried and may be more comfortable than ear muffs.

Temporary or disposable inserts such as wax, fibrous glass wool or framed plastic are reasonably effective if fitted well. Cotton is not effective, although it may seem to change the tone somewhat.

In general, protective devices designed to be worn over the ear are more effective than those used in the ear.

Lightweight ear muffs are comfortable to wear, provide good protection and are quickly put on and removed. Most models will fit over a cap and some are designed for use with a brimmed hat.

The muffs must fit well to work correctly. Make any minor adjustments you need, for just a slight opening may eliminate all of the advantages of the muff. Heavy temple pieces on eye glasses tend to keep the cushions from fitting tightly. Special foam pads are available to slip on the temple pieces to help reduce noise and increase the comfort.

Hearing protection equipment does not blot out sounds a farmer might want to hear--such as squeaks that might indicate trouble in the machinery, or conversation from another person, or a radio. These sounds are muffled, but so is the machinery. In fact, you can usually hear another voice or radio in a noisy situation better while wearing hearing protectors.

Added Noises

Tractor radios contribute to the total noise problem, for the volume must be high in order to hear the radio over the noise of the tractor. Just wearing protectors improves the situation considerably. The volume can be turned down and the reception improved. Ordinary battery headsets designed for radio reception do not give adequate protection. They do eliminate part of the higher frequency sounds and thus may appear to be somewhat satisfactory.

Unfortunately, they are of little or no value in the low frequency range where tractor noise is most intense. There are headsets available that combine protection with good radio reception. However, one can use an earpiece such as is used on transistor radios and fit the cord under the cushion of a good protector.

The Choice is Easy

Operators of noisy farm equipment really have an easy choice . . . they should get and use proper hearing protection.

The cost and inconvenience of protecting hearing is practically nothing compared to wearing hearing aids or not being able to hear at all.

While any noise reduction is better than none, it is best to be on the safe side and use more than you think you'll need.

Most people readily adjust to the use of hearing protectors and in a short time forget they are wearing them. In most cases, other advantages, such as less fatigue and stress will increase as one becomes accustomed to them. Don't over-rate the disadvantages on the basis of a short trial period.

Obviously, the time to take action is before any permanent damage is done. Have your hearing checked to determine your present condition, then avoid noisy situations . . . and protect your ears from those you can't avoid.

For further information on this subject, contact. Dr. William Field, Department of Agricultural and Biological Engineering.

RR 4/85

Cooperative Extension work in Agriculture and Home Economics, state of Indiana. Purdue University and U.S. Department of Agriculture cooperating. H. A. Wadsworth. Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Cooperative Extension Service of Purdue University is an affirmative action/equal opportunity institution.