The Science of Sound
TEACHER'S NOTES
INTRODUCTION
The experiments should each take about half an hour. They are intended to be done sequentially since they build on each other. The "Animal Challenges" are not experiments but activities that encourage the kids to apply the concepts of sound to the animal kingdom.
We've found it best if the kids can work in pairs. The complete materials list for a class of 24 is on another page. Each experiment lists the materials needed for one pair of kids. Although many of the items are generally considered disposable (cans, paper cups, etc.), please reuse them to help save the earth. Since some of the materials are not reusable, they will have to be replaced for other classes (1 toothpick, 2 alcohol wipes, 2 straws). I recommend checking that everything is there before starting this unit.
These notes provide a summary of the main points of each experiment/activity and any additional information that might be helpful or interesting.
1. MYSTERIOUS MAGIC
A. Get the children interested in sound through "magic"
B. Introduce them to the format of the experiments:
- getting materials
- following the procedure
- observing what happens
- recording results
C. Start to introduce vibrations
Notes:
Make sure the plastic is pulled tight.
2. MOVING MOLECULES
A. Introduce molecules
B. Provide a simplistic "picture" of how sound energy is passed on from one molecule to the next
3. WONDERFUL WAVES
A. Sound travels in all directions unless blocked or reflected
B. Introduce the concept of a sound wave using water to reinforce the similarity of ocean waves and sound waves
C. Introduce the idea that a wave is energy.
D. Introduce volume and its relation to energy.
Notes:
Some kids may notice that the ripples are reflected off the pan and come back to the center: this is analogous to an echo
Some kids may notice that if they make repeated drips each time the echo returns to the center, the waves will be larger.
4. REDIRECTING RIPPLES
A. Introduce the concept that you can change the direction of sound waves.
B. Reinforce the relation between volume and energy.
C. The cone is also used for a megaphone and an old-fashioned hearing aid.
D. Human Body: Introduce heartbeats and the stethoscope.
Notes:
You might try having the kids feel their pulse (on their neck is easiest) at the same time they listen to their heart beat.
You might have them count their pulse or heart beat and make a graph for the class (or otherwise compare).
5. PERFECT PITCH
A. Introduces the concept of pitch as distinct from volume.
B. Introduce the concept of making and testing a prediction.
Notes:
Pitch depends on the volume (amount) of air in the bottle. For two identical bottles, this equates to the height of the air in the bottle. The more air in the bottle, the lower the pitch.
The bottles are basically flutes.
Squeezing the bottles slightly will also change the pitch.
6. GROOVY GUITARS
A. Reinforces pitch and vibrations.
B. Pitch depends on both the thickness and the length of the strings.
C. Introduce the concept of a conclusion.
Notes:
The kids should be able to see the strings vibrate. They should also be able to notice a difference in how the two rubber bands vibrate. The fat rubber band vibrates more slowly - hence the lower pitch - although the kids may have trouble distinguishing this.
7. VIBRATING VIOLINS
A. Introduce the concept of a sound box, resonant cavity or amplifier
(three terms for essentially the same thing).
B. Revisit volume (loudness).
Notes:
This works because of the little bumps caused by the string being twisted together out of many strands. You fingers bounce over the bumps and cause the vibrations.
Violin strings are bowed across the string - not along its length. The hair on the violin bow comes from a special breed of horse that has larger-than-normal barbs on their tail hair. These barbs cause the vibrations.
8. GREAT GONGS
A. I threw this one in mainly because it was spectacular and made very nice music.
B. This is how metal percussion instruments work.
Notes:
A bell is similar but has the clapper inside the metal bell.
Different sized nails will have different pitches. If they are made of the same material, larger nails will have lower pitches.
9. BEAT THE DRUM
A. Human Body: Introduce the ear drum.
B. Realize the value of the sense of hearing.
C. Handle numeric results:
Record results in tabular form.
Compare results to class.
Bar charts/histograms.
Note:
To make the mystery sound tubes, put a samll object inside a toilet paper tube and tape paper over the ends. Use four different objects. Label the tubes A-D. Make six or more of each type of tube to give everyone in class something to do all the time.
10. RADICAL REEDS
A. Revisit pitch and vibrations:
Need vibrations to make sound.
Pitch is determined by the length of the air column.
B. Cutting off the straw is the same as cutting a hole in it - just more permanent.
C. Clarinets, oboes, saxophones, etc. use reeds.
D. All woodwinds and brass use "holes" to change the length of the air column and hence the pitch.
Notes:
Reeds are called reeds because the "pieces of wood" used for the reed of musical instruments are actually from reeds.
11. TERRIFIC TELEPHONES
A. Practical (almost) application.
B. The string has to be tight and not touching any other object. See if anyone observes that the phone won't work if the string goes slack or around a corner.
12. SONIC SPEED
A. Introduce the concept of the speed of sound. This is the speed at which the wave travels - the speed at which the ripples in the pond move.
B. Use tick marks to record results of a repetitive activity.
13. SUPER SONAR
A. Introduce echoes.
B. Give kids a simplified model of echoes and sonar.
C. Can also redo "Wonderful Waves" and look for "echoes".