http://www.ck12.org Chapter 20. Sound
Preventing Hearing Loss
Hearing loss caused by loud sounds is permanent. However, this type of hearing loss can be prevented by protecting
the ears from loud sounds.
Who Needs Hearing Protection?
People who work in jobs that expose them to loud sounds must wear hearing protectors. Examples include construc-
tion workers who work around loud machinery for many hours each day (seeFigure20.10). But anyone exposed
to loud sounds for longer than the permissible exposure time should wear hearing protectors. Many home and yard
chores and even recreational activities are loud enough to cause hearing loss if people are exposed to them for very
long.
FIGURE 20.10
Many activities expose people to danger-
ously loud sounds that can cause hearing
loss.How Hearing Protectors Work
You can see two different types of hearing protectors inFigure20.11. Earplugs are simple hearing protectors that
just muffle sounds by partially blocking all sound waves from entering the ears. This type of hearing protector is
suitable for lower noise levels, such as the noise of a lawnmower or snowmobile engine.
Electronic ear protectors work differently. They identify high-amplitude sound waves and send sound waves through
them in the opposite direction. This causes destructive interference with the waves, which reduces their amplitude
to zero or nearly zero. This changes even the loudest sounds to just a soft hiss. Sounds that people need to hear,