Stanley's Ballon Flute

What you need

1. A plastic cup or yoghurt pot.
2. A straw.
3. A narrow cardboard tube (such as from cooking foil).
4. A balloon.
5. Sticky tape or parcel tape.
6. Scissors.

What you do

1. Cut a hole in the bottom of the plastic cup big enough to insert the cardboard tube (but don't insert it yet).

2. Cut the top off the balloon and stretch it over the top of the cup. Tape the balloon down around the rim so no air can get in.

3. Cut a small hole in the side of the cup big enough to squeeze the straw through and squeeze the straw through by a couple of centimetres. Tape this into position so no air can escape.

4. Finally insert the cardboard tube in the base of the cup, far enough so that it pushes on the balloon and tape this in position.

5. Blow down the straw and be amazed at just how loud this is!

What's going on

As you blow into the cup the pressure increases, and the balloon inflates very slightly. The balloon lifts away from the cardboard tube and the air escapes bringing the balloon back down on the tube. This vibration sets up a sound wave in the tube at its natural frequency and the result is loud hum.

Special Safety Advice

No special advice