9.1 · Sound Starts with a Vibration

From Ohio 5th Grade Science Power Workbook · Chapter 9 · Lesson 9.1.

Big idea: Every sound is made by something shaking back and forth.

Learning goals: Explain what makes a sound

Identify the vibrating part of a sound source

Explain why stopping the shaking stops the sound

Something has to shake

A sound begins when an object vibrates — shakes quickly back and forth.

A drum skin shakes when it is struck. A guitar string shakes when it is plucked. Your voice comes from parts of your throat shaking.

Stop the shaking, stop the sound

Press your hand flat on a ringing drum skin and the sound stops immediately. Grab a plucked string and it goes silent at once.

That is the clearest evidence that the vibration is the sound. There is no sound without something shaking.

Worked examples

Question: A student rings a metal bowl, then touches the rim with a finger. The sound stops at once. Explain what this shows.

Steps: Ask what the bowl was doing while it made sound. Its metal was shaking back and forth very quickly.

Ask what touching it does. The finger stops the shaking.

The sound stops the moment the shaking stops, so the shaking was what was producing the sound.

Answer: It shows that the sound comes from the bowl vibrating. Stopping the vibration stops the sound immediately.

Common mistakes

Sound always needs something to shake

Sound feels like it just appears in the air, so it is easy to imagine it existing on its own.

Every sound comes from a material object shaking. No shaking object, no sound — there are no exceptions.

Check your thinking: For any sound, ask what is shaking. If you cannot find it, look harder — it is always there.

Remember

Find the shaking part

For any sound in a question, name the part that is vibrating: the drum skin, the guitar string, the speaker cone. That is where the sound is made.

Practice tip

Remember: Name the vibrating part.

Tip: A sound question can ask what is making the sound. The full-credit answer names the part that is shaking, not the whole instrument.

Written practice

A student plucks a rubber band stretched between two fingers and hears a sound. Explain where the sound comes from and how the student could stop it instantly.

Sample response: The sound comes from the rubber band shaking back and forth very quickly after it is plucked. To stop the sound instantly, the student can hold the band with a finger. That stops the vibration, and the sound stops at the same moment.

Scoring guide: 1 point: says the sound comes from the rubber band vibrating.

1 point: says touching or holding the band stops the vibration and therefore stops the sound.

Ohio assesses that sound is produced by vibrating objects, and the stop test is the evidence.