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. People who work in jobs that expose them to loud sounds must wear hearing protectors. Examples include construction workers who work around loud machinery for many hours each day. 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 too much time. You can see examples in the Figure 1.2.

how hearing protectors work

You can see two different types of hearing protectors in the Figure 1.3. 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. 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, such as the voices of co-workers, are not interfered with in this way and may be amplified instead so they can be heard more clearly. This type of hearing protector is recommended for higher noise levels and situations where its important to be able to hear lower-decibel sounds.

the ear and hearing

The ear is a complex organ that senses sound energy so we can hear. Hearing is the ability to sense sound energy and perceive sound. All of the structures of the ear that are involved in hearing must work well for a person to have normal hearing. Damage to any of the structures, through illness or injury, may cause hearing loss. Total hearing loss is called deafness.

loud sounds

The most common cause of hearing loss is exposure to loud sounds. Loud sounds can damage hair cells inside the ears. Hair cells change sound waves to electrical signals that the brain can interpret as sounds. Louder sounds, which have greater intensity than softer sounds, can damage hair cells more quickly than softer sounds. You can see the relationship between sound intensity, exposure time, and hearing loss in the following Figure 1.1. The intensity of sounds is measured in decibels (dB). Q: What is the maximum amount of time you should be exposed to a sound as intense as 100 dB? What might make a sound this intense? A: You should be exposed to a 100-dB sound for no longer than 15 minutes. An example of a sound this intense is the sound of a car horn.


instructional diagrams

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the most common cause of hearing loss is

-->  a) loud sounds.

b) infections.

c) injuries.

d) none of the above

loud sounds cause loss of hearing by damaging the tiny bones of the middle ear.

a. true

-->  b. false

louder sounds damage hearing more quickly than softer sounds.

-->  a. true

b. false

hearing loss caused by loud sounds is temporary.

a. true

-->  b. false

the permissible exposure time to a 97-decibel sound is

a) 1 minute.

b) 4 minutes.

-->  c) 30 minutes.

d) 4 hours.

diagram questions

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