Sound waves

1
Sound waves

• 6th hour
• Spring 2008

2
What is sound

• Sound is defined as A series of compression
  waves that move through a medium such as air or
  water.
• Sound is created by any vibrating object such as
  a loudspeaker, a bell, or many other things like
  someone rubbing their hands together.
• Sound can be observed in radios, TV sets, cars,
  or naturally in animals, avalanches or any
  natural thing that makes sound.

3
The Doppler Effect

• The Doppler effect is a change in the frequency
  of sound waves that results in a change in pitch
  either form high to low or vice versa.
• The Doppler effect happens when sound waves are
  compressed towards you. Causing the intervals
  between waves diminish, which translates into an
  increase in pitch. When sound waves stretch away
  from you the pitch decreases.
• The Doppler effect can be observed in ambulance
  sirens or some fire alarms.

4
Chuck Yeager andThe Sound Barrier

• General Chuck Yeager was an air force pilot in
  WWII. After the war Chuck worked as a maintenance
  officer at Muroc Army Air Force base and tested
  planes for the RD department.
• Fighter planes in the 1940s and before had
  always been falling apart or when nearing Mach 1.
  So in June of 1941 Chuck Yeager was selected to
  test the rocket-powered bell aircrafts X-1 jet.
• After several tries and 2 broken ribs from an
  off-site accident on October 14 1941 the X-1 was
  dropped from a modified B-29 super fortress and
  created the first sonic boom on earth which
  people described as some kind of thunder while
  Chuck said It nothing more than a poke through
  Jell-O.

5
Ultrasonic and Infrasonic Sound

• Ultrasonic sound waves are sounds we can hear
  from the range of 20-20,000 hertz. Infrasonic is
  any sound under 20 hertz.
• Infrasonic sounds are things like dog whistles,
  thunder, or some explosions.
• Ultrasonic sounds are any type of sounds we can
  hear naturally with just our ears.

6
Frequency and Pitchand Intensity of Sound

• If the frequency rises the pitch will rise too.
  (Directly proportional)
• When you create a high note that note will have a
  high frequency.
• When you create a low note that note has a low
  frequency.
• The intensity of sound (amplitude) is directly
  proportional to the loudness of sound.

7
Factors That Affect Sound

• 1. Type of medium (solid, liquid, or gas)
• 2. Density of medium
• 3. Elasticity of medium.
• 4. Temperature of medium.