(ultra)sound waves

• sound travels as a...

  wave
• what are sound waves caused by?

  vibrating objects - these vibrations are passed through the surrounding medium as a series of compressions and rarefactions
• a sound wave is a type of ... wave

  longitudinal
• does sound need a medium to travel through?


  yes
• are sound waves faster in solids, liquids or gases?


  solids
• why do sound waves travel faster in solids?

  sound is a mechanical wave, the particles in solids are much closer together so vibrations can pass more easily through them
• sound wave diagram

  
• you hear sound when your ear drum...

  vibrates
• ossicles

  three tiny bones in the middle ear which vibrations of sound are passed on to
• cochlea


  a coiled, bony, fluid-filled tube in the inner ear which turn vibrations from the ossicles into electrical signals that are sent to the brain
• what does the brain do with the electrical signals sent from the cochlea?


  the brain interpret these signals and allow us to hear
• different materials can convert...

  different frequencies of sound waves into vibrations
• human hearing range


  20-20000 Hz
• how is human hearing limited?

  human hearing is limited by the size and shape of our ear drum, as well as the structure of all the parts within the ear that vibrate to transfer the energy from the sound wave
• sound waves can...


  reflect and refract
• what will sound waves be refracted by?

  hard flat surfaces
• what are echos?

  reflected sound waves
• how do sound waves refract?

  when they enter different media, causing them to change speed and wavelength (while frequency stays the same)
• ultrasound is sound with frequencies higher than...

  20000 Hz
• ultrasounds get ... reflected at boundaries


  partially
• partial reflection


  when the wave hits a boundary and some of the wave is reflected and some of the wave is transmitted or refracted
• what does ultrasound being partially reflected mean?

  you can point a pulse of ultrasound at an object, and wherever there are boundaries between one substance and another, some of the ultrasound gets reflected back
• ultrasound has ... uses

  medical and industrial uses
• how can ultrasound be used to find flaws in objects such as pipes?

  ultrasound waves entering a material will usually be reflected by the far side of the material, if there is a flaw such as a crack inside the object, the wave will be reflected sooner
• why are ultrasounds more commonly used over an x-ray for viewing a foetus?

  unlike x-ray imaging, there is no ionizing radiation exposure associated with ultrasound imaging. this is because ultrasound uses sound waves instead of radiation
• how is ultrasound used in underwater exploration?

  boats and submarines use echo sounding uses high frequency sound waves to find out the depth of the water they are in or to locate objects in deep water