Make some noise – learn about sound with a “straw clarinet”

Description: This experiment shows how sound is created. Use this as an introduction to show how rapidly vibrating objects will create sound. In this case, we’ll use something as simple as a drinking straw.

Equipment needed:

Plastic drinking straws

Scissors

The Digital Bits Science Lab Experiment:

What we’re trying to do is to create a simple musical instrument out of a plastic straw. It’s pretty easy. First, cut the top of a straw into what looks like a triangle. (It may help if you squish the straw end first before cutting it – this ensures the cut is the same for the top and bottom of the straw.) When you’re done, one end of your straw should look like this:

Next, blow into the straw. You’ll need to blow pretty hard, and your lips will seal firmly around the straw right at the point where you first made the cut. You may have to move the straw back and forth a bit until you find the right place. The parts of the straw should be flat, and parallel with your tongue – don’t rotate the straw, or the noisemaking will get very difficult or impossible. When you’ve got the right technique, you’ll be rewarded with a buzzing noise coming from the end of the straw.

This is it – we’re making sound! This is the same noise-making concept as reeded musical instruments, like the clarinet and oboe: blowing air over a reed (in this case, our cut straw end) makes that reed vibrate. When it vibrates at the right speed, it makes a noise. A similar technique also allows you to talk. Your vocal cords are just like this straw: you blow air over your vocal cords, and your vocal cords vibrate, and this makes noise come out of your mouth. The difference is that in speaking, your mouth, tongue and many other factors work together. They change various parts of how the air flows and how fast your vocal cords vibrate. This control allows us to form words, sing, and make many other interesting noises.

You can use this concept with our “straw clarinet”, too: cut the straw at the other end (the end you don’t blow into). Shorten it. Make more “straw clarinets”, and cut them to several different lengths. When you blow into these, you’ll find the noise is different from each one. Finally, if you’re really talented, try blowing while changing the tightness of your lips, or varying the amount of air you’re blowing – you’ll find that the noise will change as well.

Other articles related to this topic:

• Use a squeaky balloon to teach about air pressure, vocal cords and sound waves
• Build a balloon-powered mini-hovercraft
• Learn about air pressure with a piece of paper
• See refraction in a glass of water
• Kinetic energy transfer with a drum and drumsticks