Sound waves

What are sound waves?

Vibrations that pass through the molecules of a medium.

As sound waves are longitudinal, they travel as a series of compressions and rarefactions.

What are compressions?

Regions where the vibrating particles are closest together.

What are rarefactions?

Regions where the particles are furthest apart.

How do sound waves travel through a solid?

they cause the particles inside the solid to vibrate. vibrating particles then collide with their neighbours and pass on the vibrations.

When does sound travel faster?

When particles are more densely packed. Sound travels faster in solids than liquids.

Sound cannot travel through a vacuum.

What remains the same when sound waves pass through different mediums?

Their frequency remains the same.

What happens when sound speeds up?

The wavelength gets longer (in high density materials)

What does the fact that sound changes speed as it moves through different mediums tell us?

Sound can be refracted.

It can also be reflected and absorbed.

What does sound reflect off of the most?

Hard, flat surfaces. This is what gives us echoes.

What happens when sound waves reach our ear?

• They travel along the ear canal and hit our ear drum

What happens after sound waves hit our eardrum?

• It vibrates.

• these vibrations are transmitted along the tiny bones (ossicles), through the semicircular canals and into the cochlea.

What happens once sound waves reach the cochlea?

• It converts the vibrations into electrical signals.

• These are sent along the auditory nerve to the brain. Your brain can interpret the signals as sounds.

What do higher frequencies of sound waves mean?

Higher pitched sounds.

What do more intense signals mean?

Louder noise.

What frequencies of sound can humans hear?

20Hz to 20,000Hz

Different people are slightly different. Older people often have a lower range due to wear of the cochlea and auditory nerve.