Sound

Kathleen Moore                 O. W. Holmes
                               955 W. Garfield Blvd.
                               Chicago IL 60621
                               (312) 535-9025

Objectives:

This lesson is designed for grade levels 1 - 3.
1.  To understand that sound is caused by vibration.
2.  To understand that sound travels through solids, liquids and gases.
3.  To understand that high pitched sounds are caused by more vibrations and low 
    pitched sounds are caused by fewer vibrations.

Materials Needed:

plastic ruler(s), tuning forks of 2 or 3 different pitches, ping-pong ball 
attached to a string with tape, boom-box-type radio, balloon filled with air, 
paper plate, tiny pieces of torn paper, baggie filled with water, scissors, 
several glass bottles of the same size, large container for water, styrofoam 
cups, wire coat hangers, string (different types), wire cutters, pencils (with 
wooden ball attached to the eraser end if possible), stopwatch, flower pots of 
varying sizes attached to rope, long tubes of PVC pipe cut to different lengths 
for different tones, xylophone, plastic straws, tape. 
  
Strategy:

1. Ask children if anyone knows what a vibration is.  Ask children to vibrate 
their bodies.  Write vibrate on board.  Put a plastic ruler overhanging the edge 
of a table; hit the ruler and watch it vibrate.  Ask: "Can we see the vibration?  
Can we hear the vibration?  Can we feel it?"  Show tuning fork; hit; listen; 
touch vibrating tuning fork to ping pong ball attached to a string.  Observe the
effect; ask same questions.  Pass tuning forks around so children can experience 
the sound and feel the vibration;  note differences in pitch.  Hold inflated 
balloon in front of boom-box speaker with volume turned up loud.  "Can you feel 
the vibration?  Where is it coming from?"  Place small paper plate with tiny 
pieces of paper on it on top of speaker.  (Boombox must be turned so that 
speakers are facing up.)  Observe what happens to the papers.  Explain that all 
sounds are caused by something vibrating; sound is vibration, etc. 

2. How do vibrations from tuning fork and ruler reach us as sound?  The 
vibrations cause waves to carry sound through the air.  (You will perhaps need 
to discuss waves, depending on age and experience of children.)  "We know sound 
travels through air.  Does it travel through a solid?  Put your ear on the desk. 
Tap the desk.  What do you hear?"  Try several such examples.  "Does sound 
travel through a liquid?"  Get children to talk about experiences they have had 
such as talking underwater in the bathtub or swimming pool.  Can they hear sound 
under water?  "Try putting a plastic baggie filled with water next to your ear.  
Have another child speak loudly directly into the other side of the baggie.  Can 
we hear the sound through the water?  Does sound travel through a solid, a 
liquid, and a gas (air)?  When was it the loudest?"  (through the solid)  "Why 
do you think this may be true?"  (The molecules in a solid are more tightly 
packed, so the vibration can travel without being dispersed as it does in air.) 

3. Show a child's xylophone or an autoharp.  Strike a short bar, then a long bar 
and ask children what they heard.  Do the same for the lengths of PVC pipe.  
(Hit the end of the pipes with the palm of your hand.)   Make a kazoo out of a 
plastic straw by flattening one end and cutting it into a triangular shape; 
blow.  As one person blows through the kazoo, another takes a scissors and snips  
an inch or so off the end.  Keep doing this and ask the students to notice 
what's happening to the sound as the straw gets shorter.  Help them relate the 
shortness of length to high pitch through a variety of such experiences. 

4. Now allow the children to experiment and "play" with all the materials so 
that they develop strong physical understanding of vibrations in all the ways 
that have been presented.  Have a set of 8 identical bottles and a container of 
water and have them fill the bottles with varying amounts of water.  See if they 
can match the scale of the bottles to that of the xylophone.  Give children the 
opportunity to make a string phone or wire-hanger chime.  (Tie a length of 
string to each end of a wire coat hanger.  Put the other end of each string in 
your ears, tap the hanger against something like a desk.  Listen for the ringing 
through the string.)

Performance Assessment:

1. Children must:  Arrange bottles with varying amounts of water in row 
according to pitch.  Explain the relationship between the amount of water and 
the pitch.  Tell what is vibrating.  Blow across or just into the top of each 
bottle and explain how the relationship between pitch and the amount of water in 
the bottle changes.  Hypothesize as to why this might be. 

2. Make a stereo coat hanger as explained above.  Tell how you might make one 
with a higher pitch (shorter wire).  Cut hanger with wire cutter to get 
different lengths and different pitches. 

3. Make a straw kazoo.  Listen to its pitch.  Have your partner cut off an inch 
or two with a scissors while you are blowing.  What happens to the sound?  Cut 
off another inch.  What do you notice now?

4. Listen to the sound of each tuning fork.  (Strike tuning fork on your shoe 
then put it to your ear.)  Arrange the tuning forks from highest pitch to 
lowest.  What do you notice about the forks when they look this way? 

Conclusions:

The shorter the tube (or straw, or xylophone key or amount of water in the 
bottle) the higher the pitch.  The longer the tube, the lower the pitch.  Pitch, 
(high and low) is caused by the frequency, or number, of vibrations per time. 
More vibrations per time ("bigger" frequency) = higher pitch;  fewer vibrations 
per time ("smaller" frequency) = lower pitch. 

References:

Science on a Shoestring