Subject: Re: Partials of Forks?

[Robert Scott]

David Ilvedson wrote:
  > They used an A440 fork to tune A3 (temperment starting point)
  > F3 - A3 = F3 - Fork.
  >

and Mark Schecter responded:

> Well, call me old fashioned, but this tunes the fourth partial of A3 to
> the second partial of the fork (?880), which would only yield A4=440.0by luck. They are introducing two variables; the distance betweenpartials 1 and 2 of the fork, and the distance between partials 1 and 2of A4. The sum of those differences, unless by chance it is 0.0, is the_offset_ of A4 from 440.0. At least, that's the way I figure it.

Forks do not have partials - at least not in the same sense that piano strings have partials.  When a fork is struck and held in the hand, the only sound coming from that fork is A-440.  There is no 880 at all.  So if you play the note F3 along with an A-440 fork, you will not hear any beat because 440 is not in the partial series for F3.  However, you can hear a beat if you do this:  strike the fork and then rest the support on a wooden surface, like we normally do to make the sound of the fork louder.  Now play F3 along with the "amplified" fork and suddenly you do hear the beat at 880.  What made the difference?  It is not simply that the fork is louder.  The 880 comes from the non-linear interface to the wooden surface which introduces harmonic distortion products.  These distortion products are true harmonics - exact multiples of the fundamental.  So if you do manage to coax some 880 out of a 440 fork using harmonic distortion, you can be assured it is exactly 880, not !
 880.5.

Robert Scott
Ypsilanti, Michigan