Noise abatement measures are under the jurisdiction of local government, except for occupational noise abatement efforts. It is impossible for an active person to avoid exposure to potentially harmful sound levels in today's mechanized world. Therefore, hearing specialists now recommend that individuals get into the habit of wearing protectors to reduce the annoying effects of noise. Muffs worn over the ears and inserts worn in the ears are two basic types of hearing protectors. Since ear canals are rarely the same size, inserts should be separately fitted for each ear. Protective ear muffs should be adjustable to provide a good seal around the ear, proper tension of the cups against the head, and comfort. Both types of protectors are well worth the small inconvenience they cause the wearer, and they are available at most sport stores and drugstores. Hearing protectors are recommended at work, and during recreational and home activities such as target shooting and hunting, power tool use, lawnmowing, and snowmobile riding.

The main industrial control approaches include use of sound absorption, enclosures, barriers, and vibration isolation and damping. These methods are briefly described below.

1. Most porous materials absorb sound, and those materials specially made for this purpose include porous foams and fiberglass. However, ordinary materials such as carpets and drapes are also effective, and can be used in building spaces to reduce reverberant sound buildup and noise.

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2. Enclosures can be used to partially or completely enclose machines (machine enclosures) or to enclose operators of machines (personnel enclosures). The first approach may be regarded as path control and the second as receiver control.

3. Barriers are used to shield personnel from sound sources. The effectiveness of a barrier depends not only on the effective height of the barrier but also how far the receiver point is into the sound shadow.

4. The vibration isolation of machine sources from their supports can be particularly useful in reducing the noise produced, especially if the machine is small compared with a large flexible support or enclosure that can act as a sounding board and radiate the sound. Soft metal springs or elastomeric isolators are often used as isolators.

5. Damping materials can also be effective at reducing noise when applied properly to structures if their vibration is resonant in nature. Damping materials that are viscous applied with thicknesses two or three times that of the vibrating metal panel are particularly effective.

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