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Data pubblicazione: 4-feb-2014
Flying Circus of Physics newsletter for Feb - April 2014
When I hear music from the resonance of a string or tube, my eardrums are intercepting a sound wave consisting of a series of pressure variations, very slight changes from the atmospheric pressure. The ear drum is pushed inward during the higher pressure phases and it expands outward during the lower pressure phases. The resulting oscillating of the ear drum begins the signaling that eventually brings the sound to consciousness.
The music due percussions is different, especially if it consists primarily of separate sound bursts with very little resonance. Each burst pushes the ear drum inward but there might be no phase in which the air pressure is lower than the atmospheric pressure. Of course, when a percussion instrument is played, usually there are vibrations of the struck objects, and so resonance always plays a role.
This month I have collected some of my favorite examples of percussion music in which resonance plays only a minor role --- examples that make me smile or even laugh.
A young boy plays a washing machine. There is some resonance at work here; that is why he is hitting different parts of the machine, to oscillate components with different lengths.
Cup music at Starbucks
http://www.youtube.com/watch?v=igHVBgnaU4g
The grooves cut across a road in Lancaster, California, reproduce the William Tell Overture when the tires on a car hit them at 55 miles per hour. The groove spacing was calculated to produce the frequencies required in the music; that is, the sound impulses cause the eardrum to oscillate at the correct frequencies.
http://www.youtube.com/watch?v=nU5YWhWE_AY
A person makes music as he rollerblades along a series of bottles. Xylophone hammers that are attached to the rollerblades strike the bottles. The bottle spacing was calculated so that if he moves at a certain speed, the impulses produce the proper frequencies of the eardrum.
http://www.youtube.com/watch?v=rs9CYDxcrkY
Even if you are locked up in solitary confinement, you can still make music.
http://www.wimp.com/musicalteeth/ musical teeth
http://www.dump.com/desktopdrummer/ finger drumming
http://www.youtube.com/watch?v=sb-2VsE2y-U body percussion
Basketball impacts are music to any avid basketball player.
http://www.youtube.com/watch?v=isPm79xTzM4
http://www.wimp.com/bellsbasketballs/
Well, that last one is not just percussion, of course, because resonance of the bells is certainly involved.
As always, there are hundreds of stories that the main FCP site
The main story for February 2014 is about a curious pattern I found in a glass of wine as the wine evaporated over several days. (Yes, I watched wine evaporate for days. It was boring but still better than watching paint dry, which I have done several times.) The pattern should never have happened, but after a while I realized its probable cause.
Cheers,
Jearl Walker
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