Activity: Musical straw

This week, we will make a musical instrument from a drinking straw. According to my co-workers, this is the most annoying Science by Email activity ever, at least for the people who have to listen to it.

You will need

·  A drinking straw
·  Scissors

What to do to make your musical straw

1.  Use your fingers to partially flatten about two centimetres of the straw at one end.
2.  Cut the end of the straw to make a point, about 1 to 1.5 cm long.

To play your musical straw

1.  Place the pointed end of the straw in your mouth so the point is just past your lips.
2.  Squeeze down hard with your lips. It helps to curl your lips back around your teeth so your teeth can help apply pressure.
3.  Blow through the straw
4.  As you are blowing, gradually release the pressure on your lips.
5.  When your lips are in just the right position, you will hear a buzzing sound.
It may take several attempts before you find just the right combination of where you put the straw, how hard you squeeze with your lips and how hard you blow.
Once you have the knack of playing your musical straw, here are a few other things you can try:
·  While you are playing the straw, try repeatedly cutting a couple of centimetres of the end. The sound will become higher. Stop before you cut off your nose
;-).
·  If you can find one straw that will slide inside another one, then make the larger one into a musical straw and slide the thinner one in and out of it as you blow. It will change the note as you play, like a trombone.
·  You can make small holes in your straw. By covering and uncovering the holes, you can change the pitch, like a recorder.

What's happening?

Sound is a form of vibration, which just means that sound is created by things shaking back and forth. When you blow through the straw, you make the tips of the point vibrate (you may be able to feel them with your tongue as you play). This sound waves travel through the air in the straw, then out through the end. The vibration travels through the air until it reaches your ears.
When the sound waves travelling down the straw reach the end of the straw (or a hole in the straw), some of the sound is reflected back up the straw. The sound waves travelling up and down the straw interfere with each other and produce a standing wave in the straw (See the wave machine activity at www.csiro.au/helix/sciencemail/activities/Waves.html ). The result is that the straw ends up making sound waves of a particular frequency, depending on the length of the straw. When you change the length of the straw, by cutting it, making a hole in the side or sliding two straws in and out of each other, you change the frequency it produces.

Application

Many musical instruments, including the oboe, clarinet, saxophone and bagpipes, use a thin piece of wood called a reed to make a sound. Air blowing past the reed makes it vibrate, just like the tips of the straw. Some instruments have a metal reed which performs the same job.
Most woodwind and brass instruments make different sounds by changing the length of the tube that the sound travels along. Some use valves that open holes in the side of the tube, some switch between tubes of different length and the trombone lets the player change the length of the tube by sliding it. /
Cut the end of the straw into a point.

Squeeze the straw with your lips as you blow through it. It helps to curl your lips back around your teeth so your teeth can help apply pressure.

Three ways to change the sound: cutting the straw, two sliding straws and a straw with holes in it (marked in black)