How Does Sound Travel?

By Laura Hospitál on Mar 31, 2015

A simple tuning fork is employed to help students understand more clearly what causes sound and the manner in which sound moves.  The vibration of air causes sound to travel from the point of its inception to our ears.   This activity allows students to feel vibration using a tuning fork in order to better conceptualize the movement of air around the tuning fork.  

Vocabulary:

  • Wavelength - the distance from the top (crest) of one wave to the top (crest) of the next wave
  • Frequency - the number of wave cycles/ second
  • Hertz - a measure of the number of frequency cycles/ second
  • Amplitude - the height of a wave

This activity was designed by Jim Clark.

Preparation:

  • Prepare one tuning fork for each student.  
  • Tuning forks will ideally be different pitches.

Materials

  • A tuning fork for each student (ideally of different pitches)
  • Larger tuning forks on a stand may come with a mallet.

Procedure

Warm Up:

Pass out tuning forks and have students hit them on their knee or the ball of their hands.

Part One - Pitch and frequency

  1. After students have had a few minutes to play with the tuning forks, listen separately to each student's tuning fork. What do the students notice?  (The tuning forks have different pitches.)  
  2. Read the measurement of frequency in Hertz from each tuning fork to the group.  Do the students notice a pattern?Students should notice that the higher the frequency (in Hertz) the higher the pitch of the tuning fork. Relate the speed of vibration of the tuning fork to the pitch 

Part Two - Vibration and sound

  1. What causes sound?  Ask the students to think about why they are able to hear the sound from the tuning forks.  Have them place the tuning fork close to the ear after striking it.  What is it it doing?  (vibrating) Then, have the students touch the tuning forks.  They will likely already have discovered that the tuning forks are vibrating.  Discuss with the class how the vibration of matter is what makes sound.
  2. Sound travels - How does sound travel from the tuning fork to our ears?  Discuss - What is located around the tuning fork?     If students answer "nothing", prompt them to think again until they realize that air is surrounding the tuning fork.  Describe the vibraion of the tuning fork causing the surrounding air molecules to vibrate.  This vibrating air forms sound waves.  The sounds waves travel to our ears.  

NGSS Standards:

Grade 1 - Waves, Light, and Sound

PS4.A: Wave Properties
 Sound can make matter vibrate, and vibrating matter can make sound. (1-PS4-1) PS4.B: Electromagnetic Radiation
 

Grade 4: Waves:  Waves  and Information

PS4A Wave Properties:  Waves of the same type can differ in amplitude (height of the wave) and wavelength (spacing between wave peaks).
 

Middle School: Waves and Electromagnetic Information

PS4.A: Wave Properties: A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude. (MS-PS4-1)
 A sound wave needs a medium through which it is transmitted. (MS-PS4-2)
 

High School: Waves and Electromagnetic Radiation

PS4.A: Wave Properties: The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. (HS-PS4-1)
 
 

 

 
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