Waves and Sound

• Wave


  An oscillation or vibration that transfers energy from one place to another
• Sound waves


  • Help you communicate
• Transverse waves


  • Vibrations (oscillations) move up and down, perpendicular (at right angle) to the direction of travel
  • Examples: Water Ripples, Light, On a rope/slinky, Earthquake
• Longitudinal waves


  • The oscillations are parallel to the direction of travel
  • Examples: Sound, Slinky, Earthquake
• Waves transfer energy not matter
• The direction of oscillation is at 90 degrees
• Reflection


  Waves bounce off surfaces and barriers
• Incident wave


  The wave coming into a barrier
• Reflected wave


  The wave bouncing off
• The two types of waves are Longitudinal waves and Transverse waves
• Oscilloscope


  Can be used to see sound waves
• Pitch


  How high or low a sound is
• Frequency


  On an oscilloscope trace, the pitch of a sound is shown by how many waves there are
• Eardrum


  • A thin piece of stretched skin
• Ossicles


  • Tiny bones in your ear
• Cochlea


  • A small surly tube filled with liquid
  • Lined with tiny hairs
  • When they move they send nerve signals to the brain
• How the ear works

  1. Sound goes to the pinna, then travels along the auditory canal

  2. Reaches the eardrum which vibrates

  3. Ossicles amplify the vibrations

  4. Cochlea turns vibrations into electrical signals

  5. Auditory nerve takes signals to the brain
• Human hearing range


  • 20Hz to 20,000Hz
• We all have slightly different hearing ranges
• People lose the ability to hear sounds of high frequency as they get older
• Almost 1 in 5 people suffer some sort of hearing loss
• Temporary hearing loss may be caused by ear infections and colds, after which hearing recovers
• Permanent hearing loss and deafness can be present at birth or occur if the ear is damaged or diseased
• Decibel scale examples


  • Right next to speakers at a concert - 140
  • Chainsaw - 100
  • Conversation - 40
  • Jet engine - 120/140
  • Alarm clock - 80
  • Lawnmower - 100
  • Whisper - 20
  • A vuvuzela - 130
• Sensorineural Hearing Loss


  The most common type of hearing loss, can be a result of ageing, exposure to loud noise, injury, disease, certain drugs or an inherited condition
• Tinnitus


  When you hear buzzing inside of your ear
• Sound wave


  Longitudinal wave
• Amplitude


  Distance from middle to the top
• If a sound is very high pitched


  The frequency of the wave is more
• Echo


  A reflected sound wave
• Ultrasound is used for imaging
• Ultrasound


  • Less harmful to patients
  • Non-invasive and does not expose the patient to radiation
  • Can be used for the heart
  • Waves reflect off the surface of the foetus, a machine detects this to build up an image
• Dolphin echolocation


  • Unique ability to navigate through the dark parts of the ocean
  • Echolocation is used to see the world through sound
  • Echolocation interprets the echoes of sound waves by bouncing of nearby objects
  • Sound waves are picked up in the dolphins lower jaw and sent to its brain as signals
  • Dolphins emit high frequency sound when echolocating
• Humans hearing range is 20-20,000Hz
• Bat echolocation


  • Use echolocation to see/hunt
  • The clicks and squeals emitted by bats are inaudible to humans but to bats they are extremely loud
• Sound has to travel to reduce echoes
• The speed of sound is 340m/s, which means sound travels 340 metres in one second
• Ultrasound scans can be used to look at unborn babies, tumours and internal injuries