Sound and Vibration

Vince hears a ring while the ringing object is still outside. Sound travels through air and can reach us before we see what made it. Sound is invisible; the blue curves in these pictures are symbols that help us follow it.

Ask together: What makes Vince turn toward the door?

A small striker knocks the metal chime, then moves away while the chime keeps ringing. The knock makes the metal vibrate: move back and forth very quickly. This vibration makes the ring. The slow swing of the whole chime is a different movement.

Ask together: What touches the chime before it rings?

Vince holds the metal tube, and the ringing stops. His hand reduces the metal’s vibration, so the ring dies away quickly. He touches the tube itself.

Ask together: Which part does Vince touch?

The same yellow boot presses small stones on the path and then lands on wooden boards. The stones knock and scrape against one another and the boot, making vibrations and sound. On the boards, the boot and wood vibrate. Both the surface and the step affect what Vince hears.

Ask together: What changes beneath his boots?

Vince claps once, then listens as the clap comes back from the far stone wall. Some sound reflects from the wall and returns after a short pause: an echo. The arrows help us follow its direction. A nearby wall can reflect sound without a separate echo.

Ask together: Can you follow the sound to the wall and back?

Vince taps the drum and lifts the beater away. Rice grains jump on the drumhead. The tap makes the drumhead vibrate. Contact with the moving head pushes the grains up; sound in the air does not lift them. A grown-up handles loose rice.

Ask together: What moves after Vince taps?

Vince taps a metal bowl. He hears a ring and sees ripples on the water. The bowl’s trembling wall makes sound in the air and moves the water touching it. Visible water ripples and invisible sound in air are different waves. Results depend on the bowl, its support, the water level and the tap.

Ask together: What can Vince hear? What can he see?

Vince keeps his fingers lightly in place as he hums, then stops humming. Air from the lungs makes the vocal folds vibrate. The tremble he feels stops when he stops humming; his fingers stay in place. Looking is an option, too.

Ask together: Hum, pause, then hum again. What can you feel?

Vince hears the familiar chime as he arrives home. The chime rings when its metal vibrates, just as it did at the start. A familiar sound can help us recognise a place.

Ask together: Which sound has Vince heard before?