How You Hear – Sounds and Decibels

drawing of the ear canalWhen a noise occurs, the effect caused is actually vibrations (sound waves), which are sent speeding through the air. These vibrations are then funneled into your ear canal by your outer ear. As these vibrations travel into your middle ear, they hit your eardrum, causing it to also vibrate. In turn, this sets off a chain reaction of vibrations. Smaller and thinner than the nail on your pinky finger, your eardrum vibrates the three smallest bones in your body:

  • First, the hammer
  • Then the anvil, and
  • Finally, the stirrup.

The stirrup then passes the vibrations into a coiled tube in the inner ear called the cochlea. The fluid-filled cochlea contains thousands of hair-like nerve endings called cilia. When the stirrup causes this fluid to vibrate, the cilia move. The cilia then translate these vibrations into messages for your brain, sent via the auditory nerve. The auditory nerve carries messages from 25,000 receptors in your ear to your brain, which then makes sense of the messages and tells you what sounds you’re hearing.

Scientists measure levels of sound in units called decibels. Here are some examples of various noises and their noise levels:

Noise Decibels
Whisper 20
Normal Talking 50-60
Car Traffic 70
Alarm Clock 80
Lawn Mower 95
Rock Concert 100
Jackhammer 115
Jet Engine 130
Gun Shot 140

Other Facts

  • At high elevations, changes in pressure can cause your ears to pop.
  • Children have much more sensitive ears than adults. Their ability to recognize noises is wider.
  • Animals can hear more sounds than humans.
  • Earaches are usually caused by too much fluid pressure on your eardrum. This can occur as the result of infection, allergies, or a virus.