Using Tuning Forks to Support Curriculum About Sound

Author
Kim Gordon
20 Glen Avenue, Waterville
207-872-8767
kim_gordon@fc.wtvl.k12.me.us
George Mitchell Elementary School, Waterville
 

Activity #1

Activity # 2

Activity # 3

Grade Level: 2-3 for introduction of concepts; grades 4-5 for review or reinforcement.

Overview:An important concept for young learners is that whenever a sound is heard, something is moving.  Sounds are caused by vibrational energy.  The vibration in tuning forks is readily apparent and the sounds created can be truly beautiful.  The ARC set has enough forks for each student to use one simultaneously as the class tries various activities.  Extensions reinforce the major sound concepts while using other materials.

Time Required:  As a review for older learners, many of these activities could be done in a single session.  Since sound concepts are frequently introduced as part of the second grade curriculum, shorter time periods might yield better results for these younger learners.  If the children are encouraged to experiment with the materials, three 25-45 minute sessions would be useful.

Maine Learning Results  performance indicators addressed:

Science and Technology

Energy: Students will understand concepts of energy and be able to
H 1: Identify different forms of energy (e.g., sound)
H 2: Explain different ways in which energy (sound) can be produced.

Inquiry and Problem Solving: Students will be able to
J 2: Ask questions and propose strategies to use in seeking answers; conduct scientific investigations: make observations...do experiments.
J 3: Use results in a purposeful way, which includes making predictions based on patterns they have observed.

Scientific Reasoning: Students will learn to formulate and justify ideas and make informed decisions.  Students will be able to:
K 3: Make observations.  Draw conclusions about observations.

IMPORTANT:  People naturally want to hit the tuning forks on random surfaces.  Students must be told and then reminded NOT to tap the tuning forks on the edges of tables or other surfaces, but always to tap the rubber striker.  Some young children also need specific instructions to remove the tuning fork from contact with the striker after hitting it.  Modelling appropriate use of the forks before passing them out to the students will be important.

Suggested Grouping:  The tuning forks must be struck on special strikers included in the kit.  The strikers could most efficiently be placed in the middle of a table of 4-5 heterogeneously grouped students.  The tables will offer other important possibilities during the activities.

Activity #1  The Causes of Sound

Materials: Procedure, Part A:
    Ask the children to sit in a group quietly for a moment, listening to ambient sounds and then let each name a sound that she/he heard.  Tell them that although all these sounds seem very different, all sounds are caused by the same thing.  Today they will all be sound detectives and try to find out what that thing is.
Tell them you will make a sound for them using a tuning fork.  This tuning fork always makes the same clear sound.  Show the learners that you are holding the rounded handle and that the two "tines" make a narrow letter "U".  Show the rubber strike plate.  The tines must only be struck on the strike plate, because they may become bent or broken if they are struck against a hard object.
    Tell the children to keep their eyes on the tines as you tap one of the tines on the striker.
Ask the children:  "What do you see happening to the tuning fork while it is making its sound?" (the tines are moving back and forth very quickly)
Strike the fork again to be sure that all children now see that the tines are vibrating.
Choose a volunteer to be the Sound Stopper.  This time when you strike the fork, ask the child to close his/her hands around the tines.  What happened?  (the sound stopped)  If you wish, repeat the experiment, using the shoulder, knee, or foot of the Sound Stopper to make the sound end.

Extension:  This is a good time to look at other objects that make sounds with highly visible vibrations.  Possible samples are musical items like a triangle, tambourine, guitar, drum, cymbal; household items like a wind-up clock with an alarm, a kitchen timer, a hand bell, wind chimes, etc.  In each case the children can guess what is vibrating and check their hunches by trying to stop the sound by stopping the vibration.

Procedure, Part B:
    Repeat the importance of handling the equipment correctly before sending the children to tables or work stations at which the tuning forks have been placed.

Have each child pick up a tuning fork and tap one tine of it briskly on the striker, pulling the fork back to eye level.  Each student should carefully observe the vibration.

On the next strike, have the children touch their cheeks with the vibrating fork.  What do they feel?  (It tingles)  Why?  (Because of the vibrations)  If they put a silent fork against their faces, does it tingle? (No)  What not? (Because the vibrations
Can we see vibrations travel through the air?  (No. Vibrations just like these go through the air to bring sounds to our ears, but we can't see them with our eyes.)  Remove the water containers to a safe place.
    Have the children strike the fork again.  This time ask them to let the end of the handle touch the table, while their hand moves up a bit closer to the "u" to keep the fork upright.  Has the sound changed?  (Yes, it has become louder)  Why?  (Now the vibrations are passing into the table.  Molecules in the table are vibrating, too.)
Have them repeat the process, this time putting their ears down on the table.  What do they hear?  What can they feel?
    Ask a few specific children to try placing a vibrating fork on other surfaces: a chair, a file cabinet, the floor, a book, the teacher's desk, a recess ball, a lunch box, etc.  Did they detect any patterns in what made the fork's sound louder?  The softer?  If necessary, guide their theorizing by pointing out that some things - like a rubber recess ball- have spaces filled largely with air, while others - the table- are packed quite solid.  Can the vibrations move more easily through air or a solid?
(Sound travels in waves that spread onward from the source to our ears.  All things are made up of molecules.  The molecules in solids  like metal or wood are tightly packed together and they can carry sound waves more efficiently than the spread-out molecules in air.  Solids are good transmitters of sound.  Sound travels through steel 15 times faster than through air. Water's good too, carrying sound four times faster than air.)
Let some children choose a new site to place their vibrating forks.  Ask the class to predict whether the sound will be louder or softer (i.e., whether the sound waves will travel well or be slowed down).

Extension: Sound in your railing
If your school has a metal hallway railing, you may use it to prove that sound travels better through the metal than the air.
Space your students along the railing- the longer the rail, the better.
Have someone at the front of the line tap a tuning fork and hold it in the air.  Have every child raise his/her hand if the sound can be heard from that place in line. (Children near the end shouldn't be able to hear the sound clearly.)
Now have the children place an ear on the railing.  Have the leader tap the tuning fork (on the striker, of course) and place it in contact with the railing.  The students should raise their hands when they can hear the sound.  Could more students hear the sound when it was travelling along the pipe? (Yes.)
Native Americans placed their ears on the ground to hear horses approaching; people (very carefully!!) listen for trains approaching by putting their ears on the train tracks; snakes receive all their information through these vibrations in the ground - since they don't have ears.

Activity #2: Resonance

Remind the children that the vibrations need to travel to carry the sound to our ears.  Some shapes actually make the sound louder because of the way they affect the vibrations.  If the childen have sung in a tile shower, their voices have seemer louder and fuller because the sounds they made traveled from their throats and bounced off the shower walls.  (The base of a drum or the body of a guitar or violin are other examples of good use of resonance.)
Some things stop the vibrations.  These things can be useful in "sound-proofing" a space.

Materials:


Have ready three empty 19oz. cans, taped together to form a single long tube.  Bring one of the water containers to a central location.  Put the can-tube in the water.  While holding the tube, strike an A tuning fork.  Hold the tuning fork directly above the tube horizontally.  Move the fork and tube slowly up and down in the water until you hear the fork at its loudest.
What happens?  ( The vibrating fork makes the air in the tube vibrate.  When the air column in the tube vibrates at exactly the same frequency as the tuning fork, they are in resonance and this makes the sound of the fork much louder.)
With older learners, have other can-columns ready and return the water bowls so that each group can experiment in the manner you modelled.  Have them work with forks of different pitches.  Can they notice any differences in where the can-column needs to be to create the best resonance?

Extension A:
    Many classroom science texts ask the students to use elastic bands and empty tissue boxes to create primitive guitars.  Others suggest stretching balloon pieces over the top of empty coffee cans to make drums.  If students do these activities now, they should be able to see that the sounds resonate in the empty spaces.  The sounds caused by plucking the elastics or tapping a shred of rubber are much louder than they would have been without a resonating space.  The vibrations are obvious to the eye and reinforce the main idea that sound happens when there is vibration.

Extension B:
    Challenge the children to think of the best way to "deaden" the sound of a small transistor radio - without turning down the volume or turning off the radio.  Let them speculate (as a group or in small teams) on ideas and then try some.  What happens when the radio goes in your desk drawer?  In a lunch box?  Is wrapped in a snow jacket?  Is set outside the classroom door?
What makes the sound decrease?
    Help the children to generalize that things that increase the distance between molecules and the over-all amount of air space (like the down-filled jacket), keep the sound waves from being passed along efficiently.  (Insulation in our walls helps reduce noise in our houses.)  In the hallway, the radio may sound very loud because of the resonance from the tiles.

Activity #3: The Causes of Pitch

Materials: Procedure:
The ARC tuning forks have several different pitches and the pitch of each is stamped into the metal.  Ask all the children with forks of the same pitch (perhaps all the ones marked "C") to strike and place their handles in contact with the tables.  Follow up by calling for each note in turn. Do the tuning forks sound different? (Yes.  Some sound higher and lower.  Older learners might be able to say the pitches sound different)
    Have the children compare the tuning forks at their table.  Can they see any differences?  (Some tines are longer or shorter)  Ask the child(ren) with the longest tines at each table to strike the fork.  Have the children listen.  Now ask the child(ren) with the shortest tines to strike the fork(s) as the others listen.
    Ask the children to come up with an idea or theory (a hypothesis) about the relationship between the length of the vibrating tines and the pitch of the note.  Test their hypothesis using an assortment of tuning forks that includes one of each pitch.  After the first child sets one of the forks vibrating, have successive children choose another of the folks and, after comparing their sizes, predict whether its pitch will be lower or higher than the pitch of the previous one.

Extension A:  Experiment with vocal cords
"Why are some voices high and some low?"

Materials: (for each person or each group)


Put the rubber band lengthwise around the book so that there are no twists in the band.
Slide the pencils under the band so that each pencil lies across the book at either end, parallel with the top and bottom edges of the cover.
Gently pluck the band with a finger.  Watch and listen to its vibrations.
Now move one pencil to the middle of the book, reducing the distance between the pencils.
Pluck the band between the two pencils.
How is the sound different this time?  How are the vibrations different?
    When you pluck the whole band, the vibrations are so slow that you can easily see them.  Slower vibrations give a lower sound or pitch.  When you pluck a shorter length of the band, the vibrations are so fast that you can hardly see them.
Our vocal cords are like two rubber bands that vibrate in the voice box when a person sings or speaks.  We can feel these vibrations if we put our fingers on the bony part (Adam's apple) of our throats while we speak or sing.  The front ends of our vocal cords are attached to it.  When we sing, the vibrations of the vocal cords are transferred to our Adam's apples.
Women generally have shorter vocal cords than men; children generally have shorter cords than adults.
Guitar strings and the wires in pianos are other examples of how length affects pitch.

Extension B:  Experiment with pitch & water bottles.
"Why are some pitches high and low?"

Materials: (for demonstration or for each group)

Line up the bottles on a surface the appropriate height for the students to work with.
Pour 5 in. of water into the first bottle.  Pour water into the successive bottles so that each one has about 3/4 in. more water than the one before it.
Starting with the first bottle, have someone blow across the rim of each.  The notes should go up step by step.  If not, they can be adjusted by adding or subtracting a bit of water.
    Is something vibrating here? (Yes, the air in the bottles.)
Which bottle produces the highest sound? (The one with the least air.)
The lowest?  (The one with the most air.  The more air in the bottle, the slower it vibrates and the lower the sound.)
Flutes, oboes and clarinets use a vibrating column of air to make their music.
    If you have used glass bottles, have a student tap each of the bottles with a wooden pencil, instead of blowing over them.  Something new is vibrating.  Can they guess what?  (The glass instead of the air.)

Extension C: Pitch in a cup of coffee*

Materials:

Fill the mug 3/4 full of boiling water.
Put a spoon into the water and clink its edge against the side of the mug.  Have the children listen to the pitch.
As you continue clinking, pour one spoonful of instant coffee into the water.  What happens to the pitch?  (It sounds lower.)
Continue clinking for another minute.  What happens to the pitch?  (It sounds higher.)
    The particles of coffee have tiny air bubbles attached to them.  When the coffee dissolves in the hot water, the air bubbles are released into the water.  Since sound travels through air about four times more slowly than through water, the air bubbles slow the sound waves down.  Slower sound waves give a lower pitch.  That's why the pitch is lower when you first add the coffee.  As the stirring continues, the coffee dissolves and the air bubbles rise to the top and escape.  The pitch gradually rises, returning to the original pitch when the sound waves were travelling only through the water.
This is a great demo for the children to repeat at home with a parent pouring the boiling water.

Supporting www link:
Sea turtles live in an environment where sound is much more important than vision because sounds travel further in water (and life in the delpths is dark).  Students may enjoy reading about experiments in underwater communication made with these fascinating creatures:
http://whyfiles.news.wisc.edu/shorties/turtle.html

A great resource for more hands-on sound activities for younger students:
Etta Kaner, Sound Science,  Addison-Wesley Publishing Company, Inc.: New York. 1991.

This curiculum project was funded by the Colby Partnership for Science Education, the Howard Hughes Medical Institute, and the Bell Atlantic Foundation.