Sound Waves

what are sound waves?

Sound waves are vibrations of air molecules

what happens when a sound wave contacts a solid

When a sound wave comes into contact with a solid those vibrations of air molecules can be transferred to the solid

• For example, sound waves can cause a drinking glass to vibrate

• If the glass vibrates too much the movement causes the glass to shatter

what do sound waves consist of?

• Sound is an example of a longitudinal wave, hence it consists of:

  • Compressions - regions of higher density

  • Rarefactions - regions of lower density

why do compressions and rarefaction cause in a sound wave?

• These compressions and rarefactions cause changes in pressure, which vary in time with the wave

  • Therefore, sound is a type of pressure wave

what do waves contacting solids cause in terms of pressure?

When the waves hit a solid, the variations in pressure cause the surface of the solid to vibrate in sync with the sound wave

who can sound waves be heard by and why?

Sound waves can be heard by human beings because sound waves are transferred from the air to the solid components of the ear

what are sound waves transferred by in the human ear?

• In the case of the human ear, the sound waves are transferred by two main solid components:

  • The eardrum which is made of tissue and skin

  • Three small bones

describe the journey of the sound wave in the human ear (6)

• The sound wave travels down the auditory canal towards the eardrum

  • The pressure variations created by the sound wave exert a varying force on the eardrum causing it to vibrate

  • The vibration pattern of the sound waves creates the same pattern of vibration in the eardrum

• The eardrum vibration is transferred to the three small bones

• The vibration of these small bones then transfers the vibrations to the inner ear

  • In the inner ear, nerve cells detect the sound and send a message to the brain giving the sensation of sound

Why is the range of sound humans can hear limited?

• The transmission of sound to the human ear only works over a limited range of frequencies

  • This limits the range of sound frequencies a human can hear

what is the range of frequencies a human can hear

The range of frequencies a human can hear is 20 Hz to 20 000 Hz