Lesson# 4 What Is Sound? Pitch

Waves

Lesson# 4 What is sound? Pitch

Time frame: 60 minutes

Vocabulary

Sound- Vibrations that travel through air or another medium and can be heard when they reach an ear

Pitch- A measure of the speed of the vibrations. Rapid vibrations create a high pitch while slower vibrations result in a lower tone.

Introduction

Ask students what they think sound is

Read sound article with students

Focus Activity

Divide students in groups of three or four. Give them instruction and worksheet handouts.

Materials:

●8 glass bottles (all of the bottles must be the same size)

●Water

●Spoon

Conclusion:

Discuss worksheet with students and if necessary explain the following:

Sound comes from vibrations. When you hit the bottle with the spoon, it makes the glass vibrate. When you fill the bottle with water, the glass cannot vibrate as much. Fast vibrations make a high sound and slow vibrations make a low sound. A full bottle will produce a slow vibration and a low sound. An empty bottle will have a faster vibration and a higher sound.

Clinking the bottle and blowing in it do not produce the same sound. Blowing into the bottle makes the air vibrate while hitting the glass makes the glass vibrate.

As you blow air across the lip of the bottle, the air inside the bottle flows out as new air flows back into the bottle. Pitch is a measure of the speed of the vibration. Rapid vibrations create a high pitch while slower vibrations result in a lower tone. You probably noticed that the pitch of the sound from the bottle changes as you add or subtract water. An empty bottle produces a lower pitch because the force of your breath is spread across a larger space of air. Adding water to the bottle decreases the amount of air space which means the power of your breath will affect the air more strongly. These vibrations happen more quickly and produce a higher pitch.

If time:

Make harmonicas with the students. Explain that the harder they blow, the higher the frequency of the transverse air movement, the higher the pitch of the sound. The softer they blow, the opposite phenomenon occurs.

Materials per harmonica:

2 popsicle sticks

3 rubber bands (1 thick, 2 thin)

2 one inch cut straws

1) Put the thick rubber band around one popsicle stick long-ways

2) Stick the straws under the rubber band, one on each side

3) Put the other popsicle stick on top

4) Wrap the thin rubber bands around the popsicle sticks outside of where the straws are on either end

5) Blow!