Changing Sound Pitch with a Vibrating Ruler
About this lesson
In pairs, children hold a ruler over the edge of a desk, flick it, and listen as they change how far it sticks out. They practise observing, recording results, and linking the length of a vibrating object to high and low sounds. You need one ruler per pair and scrap paper. It takes about 15 minutes.
- Grade
- 4
- Subject
- Science
- Time
- 15 min
- Prep
- 2 min
Objective
Students will explain that a shorter vibrating part vibrates faster and makes a higher pitch, while a longer vibrating part vibrates slower and makes a lower pitch.
Prep
2 min: draw a chart on the board with rows for 25 cm, 20 cm, 15 cm and 10 cm
Materials
- 30 cm rulers (one per pair)
- scrap paper
- pencils
Steps
- Say: 'Sound is made when something vibrates. Today we will find out what makes a sound higher or lower.' Show how to press one end of a ruler firmly on the desk and gently flick the end that sticks out, keeping faces away from it.
- In pairs, one partner holds the ruler so 25 cm sticks out over the edge and flicks it while the other listens and watches how fast it moves, then they switch jobs.
- Have pairs repeat with 20 cm, 15 cm and 10 cm sticking out, writing beside each length on scrap paper whether the sound was lower or higher and whether the ruler moved slowly or quickly.
- Bring the class together, fill in the board chart from pairs' answers, and ask: 'What pattern do you see between the length and the pitch?'
- Agree on the rule together and write it on the board: shorter vibrating part, faster vibrations, higher pitch; longer vibrating part, slower vibrations, lower pitch.
Quick Check
Ask each child to show a thumbs up for 'higher' or thumbs down for 'lower' when you ask what happens to the pitch if the ruler sticks out only 5 cm, then call on one child to explain why.
Differentiation
Make it easier: Test only two lengths, 25 cm and 10 cm, so the difference in sound is easy to hear.
Make it harder: Ask pairs to predict the pitch for 12 cm and 22 cm before testing, then connect the rule to a real instrument such as guitar strings or xylophone bars.
Good For
- Before lunch
- Supply teacher
- Review
- End of day
