Audiology

An audiology exam tests your ability to hear sounds. Sounds vary according to the intensity (volume or loudness) and the tone (the speed of sound wave vibrations).

Hearing occurs when sound waves move to the nerves of the inner ear and then the brain. Sound waves can travel to the inner ear by air conduction (through the ear canal, eardrum, and bones of the middle ear) or bone conduction (through the bones around and behind the ear).

INTENSITY of sound is measured in decibels (dB):

• A whisper is about 20 dB
• Loud music (some concerts) is around 80 to 120 dB
• A jet engine is about 140 to 180 dB

Usually, sounds greater than 85 dB can cause hearing loss in a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time.

TONE of sound is measured in cycles per second (cps) or Hertz:

• Low bass tones range around 50 to 60 Hz
• Shrill, high-pitched tones range around 10,000 Hz or higher

The normal range of human hearing is about 20 Hz to 20,000 Hz, and some animals can hear up to about 50,000 Hz.