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How Fast Does Sound Move?

Previously, you learned that energy travels from the interior of Earth to the surface as earthquakes or volcanoes. Each of these forces brings a great amount of energy to the surface of Earth. Does the energy of a wave travel at the same rate of speed in all materials? In this activity you will compare the speed of sound in air with the speed of sound as it travels through other materials. Some materials that you might test include a brick wall, a steel fence, or wood floor. You need to have a friend help you accomplish this activity.

Materials
  • Block of wood (or a bat)
  • Steel fence rail about 50 m long (or some other rail like rail road track)
  • Wood floor
  • Long brick wall

Procedure

  1. Measure the distance from the person striking the fence rail to the person listening. Hint: a greater distance will give you better results.
  1. One person needs to strike the steel fence while the second person listens for the sound. Now that you know what you are looking for - do it again!
    • This second time, place one ear against the steel fence rail while you listen with your other ear for sound traveling through the air. As your partner strikes the rail again, listen for the sound in the rail AND for the sound in the air. Which arrives first?
  1. Repeat the test usiing a different materials.
Safety concerns: . As with all science lab activities, the most important safety rule is to follow all teacher directions.

Extension:

Try to calculate the rate that sound actually travels through these materials. Measure the distance between the person hitting and the person listening. Time how long it takes for the sound to travel through the material. Remember to compare the time and distance with air.
 

Analysis:

  1. Does the sound travel faster through air or the steel fence rail?
  2. What factor causes sound to travel faster in air at 25° C than it does at 0°C?
    Density Elasticity Temperature Phase of Matter
  3. What factor causes sound to travel slower in rubber (which is a solid) than in air (which is a gas)?
    Density Elasticity Temperature Phase of Matter
  4. What material allowed sound to travel the fastest?
  5. Which material allowed sound waves to travel the slowest?

Review science lab safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information: the title of the activity, the URL (Internet address), and your name. Remember that no pictures can be used which show any student faces or has a student name on it.

Updated August 13, 2005 by: Glen Westbroek

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