physics sound

• Waves


  Transfer energy from one place to another, without transferring any material
• Types of wave


  • Longitudinal
  • Transverse
• Transverse waves


  • Caused by a vibration that is perpendicular to the direction of wave travel
• Longitudinal waves


  • Caused by a vibration that is parallel to the direction of wave travel
• Demonstrating waves


  • Slinky (transverse and longitudinal)
• Compression


  Where particles in the wave are closest together
• Rarefaction


  Where particles in the wave are furthest apart
• Displacement


  How far a point on the wave is from the rest position
• Wavelength


  Distance from peak to peak (or any complete wave cycle)
• Amplitude


  Maximum displacement of wave
• Frequency


  Measure of how many sound waves pass a point every second
• Frequency of sound wave

  Related to the pitch of the sound wave
• Higher frequency


  Higher pitch
• Amplitude of sound wave

  Related to the loudness
• Larger amplitude


  Louder sound wave
• Turning a sound wave into an electrical signal

  1. Sound wave vibrates a diaphragm in the microphone

  2. Produces an electrical signal
• How our ears detect sound waves


  1. Sound waves vibrate our ear drum

  2. Vibrations turned into electrical signals

  3. Sent to the brain and interpreted as a sound
• Sound waves


  Need particles (a medium) to travel
• Sound cannot travel in a vacuum (where there are no particles)
• Speed of sound in air

  Approximately 340 m/s
• The speed of sound depends on the pressure and temperature of the air
• Sound travels


  Faster in liquids and solids than in air
• Speed of sound in water

  Approximately 1500 m/s
• Speed of sound in steel

  Over 3000 m/s
• Usually, sound travels slowest in gases and fastest in solids
• Measuring the speed of sound in air

  1. Use an echo

  2. Echo is a reflection of a sound wave from a surface
• Getting a more accurate reading for the speed of sound

  1. Use a microphone attached to an oscilloscope

  2. Oscilloscope shows a pulse for when the initial sound is made

  3. Oscilloscope shows a pulse for when the reflected sound returns

  4. Removes error due to human reaction time
• When sound is reflected from a medium some sound is absorbed
• Not all of the sound will be reflected back