Activity 1.6 - How fast sound travels?

Learning Aims:
  • Understanding the speed of sound is lower then the speed of light
  • Determining the speed of sound in air by using the echo method
  • Understanding that the speed of sound depends on the medium
Materials:
A sound sensor, interface and software that displays sound waveforms (e.g. CMA Coach 6), 1-m long cardboard or plastic tube
Suggestions for use:

Show a video clip of lightening in the sky. Hand out Classroom Material: How fast sound travels? (Part I) and ask students to answer question 1. Discuss with students why we see the light before we hear the sound.

Then divide students into groups to work with computers. Hand out Classroom Material: How fast sound travels? (Part II) and let students perform computer measurements to determine the speed of sound in air. If needed help students to set up the experiment and perform measurements with the computer.

Once students have completed their investigations compare the sound speed values determined by students with the theoretical value. Here you can also discuss more examples of the use of echoes (ships navigation, animals using “echolocation” etc.) Let students find out the speed of sound in other materials. Discuss whether sound travels better in liquids, gases, or solids?
Possible questions:
  • Why do you see lightning before you hear thunder?
  • What is the measurement method used to calculate the speed of sound in air?
  • How do you calculate the speed?
  • What do you think can influence the speed of sound?
  • In which materials the speed of sound is the highest?
  • In which materials the speed of sound is the lowest?