Water Whistle - Sick Science!

A wet and musical exploration into the science of sound

People have told us that we do things to our own tune around Steve Spangler Science. At first we didn't know what they meant, but then we decided that they had to be talking about our Water Whistle experiment. We've created an instrument out of nothing more than a drinking straw and a glass of water. It's musical and fun as well as a great lesson in vibration, sound, and pitch.

Materials

Drinking straw
Pair of scissors
Cup or glass
Water

Experiment
Video
Related Experiments
Reviews

Using your scissors, cut partially through the straw 1/3 of the way down the straw. The cut should be ALMOST all the way through the straw but leave a small piece uncut to keep the two straw sections attached.
Bend the straw into a right angle at the cut being carful not to break the straw segments clean of each other.
Fill a cup or glass 3/4 full with water.
Slide the longer section of straw into the water.
Keeping the straw at a 90 degree angle, place your lips on the shorter end of the straw and blow with a light, constant breath. What do you hear?
If you are having trouble producing a whistling sound, try pinching the top of the long end of the straw.
Once you've got your Water Whistle making a constant, steady sound, trying raising or lowering the straw within the water. What happens to the pitch of your Water Whistle when you do this?

How does it work?

The Water Whistle is fun and makes a cool noise, but is there really science behind it? There sure is! The sounds of science find their basis in vibration. All sounds, from your car stereo, a saxophone, or a car driving by, are actually sound waves. These sound waves are vibrations traveling through the air the reach your ears.

Now the Water Whistle actual works through the vibration of air itself and, more specifically, the column of air inside the straw. The longer segment of straw that you have partially submerged in water is full of air and water (the amount of each depends on how deep you have your straw in the water). When you blow the air across the top of of the longer straw segment, you are causing the column of air to vibrate.

This vibrating column of air creates the whistling sound you hear. The pitch of the whistling is dependent on how much air you allow to be inside the straw. The more air that is inside of the straw, the lower the pitch of the whistle. Less air is going to create a higher pitch.

Additional Info

Pretty cool, right? Here's how you can take the Water Whistle a step further. Try different types of straws out. What happens if you use a thicker straw? A thinner straw? Try different liquids. Does the pitch change in soda or milk?

Chorus of whistles

Sandra Taylor - May 23, 2012

This user gave 5/5 stars

We made the whilste straws today and the kids loved them. Took them just a minute to see how the pitch changed with the height of the straw in water. They started changing angles of the straw to see if that made a different sound.