Vibrations & Sound

Activities to try

1. 1

   Spot the vibration: a hunt across sound-makers

   Why it works: Every sound is made by something vibrating — even when the movement is too small or too fast to see, and in a wind instrument the main vibrating thing is the air inside. Depending on the source, the vibration can sometimes be revealed by feeling a buzz, by light grains that bounce, or (for a tuning fork) by splashing water.

   1. Make a sound with an obviously-vibrating source and find the vibration: tap a drum with grains of rice or salt resting on the skin and watch them leap and skitter; pluck a stretched elastic band or guitar string and watch it blur into visible to-and-fro.
   2. Hum or speak with your fingers gently on your throat; describe the buzz you feel and say where the sound comes from.
   3. Now try a source that looks perfectly still — a struck wooden block, two clinked stones, a recorder or other wind instrument. Before testing, say whether you think anything is vibrating.
   4. Hunt for the hidden vibration in more than one way, choosing a method that suits the source: touch the struck block or stones straight after striking to try to feel a brief buzz (it fades quickly, so it may be faint); rest light grains on a sounding object and watch whether they bounce; for a recorder or other wind instrument, remember the main vibrating part is the air inside, so rest your fingers lightly on the instrument while it plays and notice the sound stops when the blowing stops; dip a sounding tuning fork in water to see it splash; touch a sounding tuning fork gently to your cheek to feel it; or hold its base against a table to hear it louder.
   5. For each source, place or say a 'what's vibrating?' tag naming the part that moves (for a wind instrument, the air inside it).
2. 2

   The reverse direction: sound makes things vibrate

   Why it works: Sound carries energy that can shake things, so the link runs both ways: vibration makes sound, and sound makes matter vibrate.

   1. Rest a few grains of rice on a drum skin. Predict what will happen to the rice when you shout right next to the drum (without touching it) — and say why before you try.
   2. Play a loud, low sound from a speaker near the drum, or shout beside it without touching or blowing on it, and watch whether the rice jumps (the sound may need to be loud and close).
   3. Hold a light paper flag or small strip of paper in front of a speaker playing a loud, low sound; watch whether it flutters, and compare with the speaker switched off.
   4. Explain what pushed the rice / fluttered the paper, and what this shows about sound.
3. 3

   Check: hidden vibration and reverse direction

   Why it works: A secure understanding insists there must be a hidden vibration even in a still-looking block, proposes a way to reveal it, and accepts that sound can make things vibrate too.

   1. Consider: 'You tap a solid wooden block and it makes a sound, but you can't SEE it moving at all. Your friend says the sound is just because you hit it hard — nothing is vibrating. What do you really think is happening, and how could we check?'
   2. State whether something is vibrating and propose a concrete way to reveal the hidden vibration.
   3. Match several sources to what is vibrating in each, including at least one where the vibration is invisible.
   4. Decide, with reasons, whether this statement is right: 'A sound can make something else vibrate.'