The Vibrational Nature of Sound

Lorna J. Holliday              Horace Mann School
Eugenia L. Sampson             Horace Mann School



Objective:

     Students will understand sound frequency, pitch, and conduction using the 
string telephone, tuning fork and musical glasses experiments.  This lesson 
could be focused on any grade level. 

Materials Needed:

4 tuning forks                 dowel rod
10 paper cups                  4 beakers
10 rulers                      water
4 ping pong balls              various noise makers
8 drinking glasses             8 soda pop bottles
14 plastic bags                slinky
pencils                        rubber mallet
string

Strategy:

Introduction to Sounds
     Make noises using whistles, noise makers, hand crackers, whizzers and any 
other loud sounds.

Brainstorm
     How do we experience sound?

Vocabulary experience - mini experiments
     sound (ruler on desk)
     frequency (slinky)
     pitch (slinky)
     conduction (ruler on desk)     

Activity 1: The String Telephone  (Groups of 2)

1) Take two paper cups and poke a small hole in the bottom of each with a 
pencil (make sure the pencil is sharpened and that the hole is just large enough 
to pass the string through). 

2) Pass one end of string (2-3 meters in length) through each hole and tie a 
knot on the inside of the cup, so the string runs between from bottom to bottom.

3) Each partner takes a cup and stretchs the string out between them, making 
sure the string is taut.  Take turns, with one partner talking quietly and the 
other listening. 

4) After each partner has had a turn talking and listening, experiment by 
pinching the string at various points while talking.  Notice what happens to the
sound.  Try loosening and tightening the string and observe the effect this has.

Activity 2: Tuning Fork Experiment (Groups of 4/5)
      Tuning forks are delicate instruments, which should be struck on a rubber 
sounding block (rubber soled shoe) and held only by the handle.  Try to avoid 
bending or dropping them.

1) Using the tuning fork with the string telephone made in Activity 1, place the
vibrating tuning fork on the string.

2) Strike a tuning fork with a rubber mallet.  Hold the vibrating end to your 
ear.  Exchange tuning forks.

3) Repeat Step 2 three (3) times, until you have tried all 4 tuning forks.  Try 
to correlate the differences you hear between the different tuning forks and the 
frequency values (numbers) on them.

4) Touch the handle of a vibrating tuning fork to the top of an empty desk or 
table.

5) Touch the vibrating end of the tuning fork to a ping-pong ball suspended from 
a string.

6) Gently place the vibrating tuning fork in a beaker of water.  Observe what 
happens to the water and to the pitch and duration of sound.

Activity 3: Musical Glasses  (Teacher Demo)
     Gather eight drinking glasses and eight soda pop bottles (each of the same 
size) and fill them with different amounts of water.  Strike each glass gently 
with a piece of wooden doweling or a pencil (be careful not to break the glass). 
Note what happens.  Try adjusting the amounts of water in each glasses to 
produce a musical scale.  For the soda pop bottles, try blowing air across the 
top of each bottle.  Observe what effects this has. 

Culminating Activity:
     Allow students to make noise with assorted toy noise makers.

Performance Assessment:

- Write up experiment using Scientific Method
- Discuss observations and findings
- Make predictions
- Draw conclusions
- Explain in pictures/words the vocabulary

Conclusion:

     This lesson is designed to provide hands on experience with the concepts of 
sound and its properties.  Given an expanded time slot, each grouping of 
activities could require an entire class period with follow-up activities. 
Follow-up activities have not been suggested to allow for grade level tailoring.

References:

Cash, Terry.  101 Physics Tricks; Sterling Publishing Co., Inc.  New York, 
1992.  p. 32-36.

Herbert, Don and Ruchlis, Hy. Mr. Wizard's 400 Experiments In Science; Book
Lab.  North Bergen, New York, 1968.  p. 69-72.

Houston, Jack.  Basic Skills Science Workbook; ESP Inc.  Largo, Florida, 1993.
p. 15-20.

Spiepak, Karen Lee.  Sound (Step - by - Step Science Series); Carson -
Dellossa Publishing Co., Inc.  Greenboro, N. C. 1994.

Talk About Sound; The Physics of Sound in Pictures and Diagrams;  Illinois
Bell Telephone Co., Chicago, Il. 1959.