Tuesday, April 19

blog 13: the (un)lucky blog

Since we're allowed to use photos from the series of tubes this week, I thought I'd talk about something for which I wouldn't be able to obtain my own picture: Franklin's Glass Armonica.

This is a nifty instrument our friend Ben Franklin contrived. Franklin (according to wikipedia) got the idea for the way the glasses are arrayed after seeing water-filled glasses being played. Instead of rotating the fingers along the glasses' edges, the glasses of the armonica are mounted on a main shaft-spindle thingy which turns by means of a foot pedal. Thus, sound can be produced by lightly placing moistened fingers (presumably the player's own) on the glasses. 

See how the glass bowls go from big to small? That's so different notes can be played. The big ones produce lower notes, and the little ones produce higher notes. This works because natural frequency varies with several properties including material, shape, and size. As the bowls get bigger, the natural frequency gets lower, and the note also gets lower. Too bad the glass armonica is not a very common instrument because of those pesky rumors that those who play it suffer bad luck and-slash-or madness.

If you'd like to hear about what it sounds like, I suggest getting out any expensive, delicate wineglasses you have stashed away in your house. (Delicate ones work better for me than glasses with thicker sides.) Wet a finger and run it along the edge of the glass (getting it to produce sound may take a few tries). Once you've got that, try adding water to the glass for different notes. It's fun for the whole family! If you've got impressionable young children with poor motor skills in the house, definitely encourage them to try, too. Don't mention my name.