34.20 Hearing and Balance

34.20.2 Describe the basic anatomy (structure) of the ear.

Our ears enable us to hear, but additionally help us to maintain our balance. 

The external ear is a passage connecting the eardrum to atmosphere. 

Sounds create pressure variations which cause the ear drum to vibrate. 

This vibration is transferred to the fluid filled cochlea through a series of small bones in the middle ear. 

Nerves in the cochlea transmit the vibrations as electrical impulses to the brain, where they are interpreted as sounds.

34.20.4 Describe the physiology (function) of the ear.

34.20.6 Describe the effect of prolonged noise exposure on hearing.

Noise is unwanted sound energy. It is measured in decibels.

If loud enough, or present for prolonged periods, noise can permanently damage human hearing.

Exposure to moderate amounts of noise (90 -100 dB) for a short time can lead to a temporary reduction in hearing ability.  If the noise is then avoided, hearing will return to normal over the next 12 hours.

34.20.8 Describe methods of protecting hearing.

Pilots must ensure they protect their ears from noise at all times.

Earplugs can be worn in addition to earmuffs and headsets to provide extra hearing protection in very noisy environments.