Sunday 27 December 2009

These instruments are rubbish

Before you consign the debris from your seasonal festivities to landfill and the recycling banks why not have some fun with it first? That is certainly my own intention and I'm starting with some fizzy drinks cans. I had a grand plan which I'll reveal tomorrow but on the way I noticed a thing or two. You may know that all plastic bottles of the same size play the same note if blown like a flute. Well aluminium cans are the same although it is not nearly as easy to produce a sound in this way. However, when you twang the ring-pull (which remains attached to the modern can after opening) the pitch varies betrween cans. Of the five cans I tried the pitch varied between G and Bb. These cans were all the same brand from the same multipack. Although the cans all contain the same volume of air there must be other variations in their construction.

The next thing I did was to twang the ring-pull as I gradually filled a can with water. It requires a steady hand. (Using a funnel has a deadening effect.) Why not try this now? I'll post a movie of my own experiment tomorrow. Before you begin, though, what do think will happen to the sound as you pour in the water? Does experience tally with your prediction?

5 comments:

  1. Going out on a limb, now, I think the pitch would rise as you fill them; I'm going to have to go and see now.

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  2. Have we got a Eco-Gamalan in the making?

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  3. I've dreamed of a junk gamelan since I first played on Gamelan Venerable Enchanter, Norfolk's own gamelan. But on today's showing, don't hold your breath!

    So, Cogitator, what transpired? Or are you still mopping up after flooding the kitchen in the name of science?

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  4. Hi J, I have to confess that I got distracted immediately. I can't even verify your results as above.... Sorry :(

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  5. Then I shall have to dream up some more compelling experiment for you. I'm hoping the opportunity to wreak havoc with real water will be sufficient to engage next term's primary school kids.

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