Physics Puzzle: the Tuning Fork
May 25th, 2009
| Categories: Music and Audio
Piano tuners use tuning forks such as the one in the image below to tune the piano. The tuning process itself makes use of a phenomenon known as beats, discussed previously on this blog: when struck, the fork emits a particular frequency against which the piano’s frequencies are compared and tuned. However, this week’s puzzle isn’t concerned with the actual tuning process, but with the fork’s general shape and appearance.
Strike a metal tube and it emits a definite frequency as well. So, why use two prongs? Why not settle for one? And if two work better than one, why not go for more? How about three? Or four?
EDITED, 30/May/2009: a solution has been added in the comments section.
SOLUTION ADDED, 30/May/2009:
The prongs of a tuning fork vibrate in anti-phase, meaning they bend inwards and outwards together once struck. This means the center of mass of the system does not move, ergo it dissipates much less energy when struck and held by the tuner’s hand. This allows for the sound to sustain for much longer. There are also other, secondary reasons, such as the ‘cleaner’ harmonic content of the fork’s ringing, having fewer overtones.
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