FREQUENCY OR PITCH
 

FREQUENCY OR PITCH
INTRODUCTION
In music if we say a note is high or low, we are not talking about how loud it is. We are talking about its pitch.

WHAT YOU NEED
2 plastic soda bottles, rubbing alcohol, water

WHAT YOU DO

  1. Wipe the top of the bottles with alcohol. This will kill any germs on the bottle before you put it near your mouth. Do not switch bottles with anyone else or you will also be sharing germs.
  2. Fill one of the bottles half way with water.
  3. You and your partner each take one of the bottles. Gently blow across the top of the bottle until you can make a sound. Hint: your lower lip and your chin must both touch the bottle.
  4. When both you and your partner can make sounds, take turns listening to each. The difference in the sounds is a difference in pitch.

Does the bottle with a higher pitch have more or less air in it than the bottle with the lower pitch?

PREDICTION
What do you think would happen to the pitch if you had less air (more water) in the bottle with water? Will the pitch be:
___ Higher
___ Lower

Fill the empty bottle 3/4 of the way full with water so that it now has less air that the other bottle. Try blowing into it. With less air (more water), the pitch is ________

Sound Box
Materials
shoe box, thick and thin elastic bands, extra cardboard - optional

  1. Put the elastics around the box.
  2. Use your finger to pluck each elastic. Listen to the different sounds.
  3. Use the fingers of one hand to stretch one of the elastics. Pluck the elastic. Does it change the note?
  4. Arrange the elastics in sequence from the highest note to the lowest note. Can you figure out why this sequence works?

Note:   you may need to tape the small piece of cardboard to the bottom and sides of the box to strengthen the sides.

What Should Happen
The elastics vibrate when they are plucked. Both the object that is vibrating, and the tension will change the sound. Wide elastics usually vibrate slower, so they create low notes. Thin elastics vibrate faster to create higher notes.

A loose elastic will vibrate more slowly (creating a lower note) than a tight elastic that is the same width. That’s why stretching the elastic changed the sound.

Virginia Standards of Learning Connection – Science
Third Grade – 3.1
Fourth Grade – 4.1
Fifth Grade – 5.2

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