Straw horns

Growing up, we were often doing science experiments around the house, in the yard and in (our favorite place) restaurants. We would often hear about potential experiments from others and knew we had to try them. Once we even got an idea for something to try from a half second of a panning shot in the TV show Northern Exposure. To this day, I’m not sure why my dad thought it would be a good idea to trust that fleeting moment of video enough to plug a pickle into a wall outlet (in a semi abandoned building) to see if it would glow, but that’s another story.

One experiment that we always came back to was the straw horn or musical straw. It makes such a wonderful noise and in quiet, fancy restaurants, there are few things more satisfying than seeing the expression on people’s faces when it sounds like a duck just wandered in off the street. I’m sure there are many waiters who still regret loaning us scissors with absolutely no idea how we were planning to use them. It’s such a simple experiment and those are often the best. Luckily there are so many ways you can change the straw to alter the note, that it always seems like there is something new to try. What if you cut the straw shorter? What if you punch holes in the straw? What if you attach another straw to the end? What if you try to play two at once? What if…

I hope you have as much fun with these straw horns as we have and if you get any great recordings (or get kicked out of a restaurant), please let me know.

No, they are not smoking. They just learned to play the musical straw and my arm is signaling when each person should play their straw to complete a round of “Twinkle, Twinkle Little Star”

Challenge:

Can you make music with a straw?

Supplies:

  • Plastic drinking straw
  • Scissors

What to do:

  • Flatten the end with fingers or teeth
  • Cut to a point
  • Put the pointed end in your mouth & blow

Three stages of making a musical straw.

Inquiry Questions:

  • What happens if you cut the straw shorter?
  • How could you make the note lower?
  • How can you get multiple notes from one straw?

What’s happening?

By flattening the straw, you weaken the plastic which allows it to bend easily. Cutting it to a point adds to this so that when you blow through it, the air causes the points to vibrate up and down. These vibrations cause the air around the straw to vibrate as well which is what you hear.

The length of the straw impacts the note because certain frequencies will naturally resonate within the straw. By changing the length of the straw (by cutting it, covering/opening holes or creating a slide) you can change the note it plays. Can you play a song using only one straw?

To calculate the approximate frequency of the straw, you can use the following equation:

f=(nv)/(2L)

Where f is the frequency, n is a positive integer (usually 1), v is the speed of sound (343 meters/second) and L is the length of the straw.

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