We hear sound every day with our ears.
Sound is a vibration, an energy, that moves in waves.
Every species hears sound at different frequencies - for example, dogs can hear very high sounds that humans are unable to hear.
Sound can move through the air (gasses), liquids and most solids.
Sound can be measured in a number of ways:
- Frequency - Sound has a frequency - high or low. Dogs can hear higher frequencies than humans can.
- Amplitude - Sound has an amplitude - how loud it is.
- Intensity - Sound has an intensity - ie one voice has a lower intensity than 100 voices singing together.
- Speed - How fast the sound wave moves
- Direction - Where the sound wave travels from and to.
Sound volume is measured in decibels.
The human ear is designed to collect sound waves
The outer ear collects sound waves
Sound waves travel down the ear canal and hit the eardrum
The eardrum vibrates and moves the tiny bones in the inner ear.
The inner ear bones carry the vibrations to a fluid filled tube called the cochlea in the inner ear.
The fluid inside the cochlea vibrates a series of tiny hairs called cilia.
Cilia are attached to auditory nerves.
The movement of the cilia stimulate the nerves - they then send signals to the brain.
The brain processes the signals into the sounds we hear.
Sound Facts
The loudest natural sounds ever made on earth are probably gigantic volcano eruptions
Space rockets blasting off from a launch pad are probably the loudest man made sounds
Wine glasses can shatter when singers hit notes which vibrate them until they break.
Whales can use intense blasts of sound to stun their prey
Exposure to loud sound can lead to hearing loss or deafness. Ear protectors have to be worn in many noisy jobs to prevent workers from going deaf.
