Students were given a
straw each and they they cut the tip to make a straw flute. They blew air and
could hear the sound the sound increased as they cut the straw.
Blowing air at the end
of the straw makes the two pieces of the tip vibrate together. The vibration
travels down the straw, and this sets up a wave in the air in the straw. The
vibration will bounce back and forth between the two ends. The vibration moves
through air molecules in the atmosphere until it hits your ear drum. It is this
vibration THAT we hear. Changing the length of the straw changes the time
necessary for the vibration to travel up or down the straw, and so changes the
pitch.
