Herb, I am a little puzzled by what you write. Guessing at what you might be doing, I would say that your fundamental in roughly at 300Hz. Observing a frequency in that range for 0.3 seconds gives you about 100 oscillations. With 100 oscillations, the accuracy of the measured frequency cannot exceed 1%, because you might have failed to account for roughly a cycle. Whatever your do, Fourier transformations included, suffers from this fundamental limitation, and to get better accuracy you need either more time or a higher frequency.
In other words, given that 1200 x log_2(101/100) = 17, a measurement of a frequency in the 300Hz range derived from a 0.3 sec. observation cannot produce a result with an error smaller than about 10 cents, which is bigger than the effects you seem to talking about, but maybe I am incorrectly interpreting your email. Peter. On Thu, 1 Jan 2009, Herbert Ward wrote: > > > Using computerized Fourier analysis, I measured spectra > of lute sound, using all strings in courses 1-6, plucked > with good tone. > > Several unexpected features cropped up. > > 1. The pitch of a harmonic often shifts over the duration > of the note, up to 10 cents. > > 2. The volumes of the harmonics often change relative > to each other. Sometimes this can be a strong and > surprising effect, as when the fundamental is basically > absent during the initial 0.3 second, and then assumes > dominance over the harmonics as the note dies away. > > 3. The harmonics' pitches are not consistent with each other, > especially during the initial 0.3 second. For example, > the fundamental can be at -4 cents, and the first harmonic > (an octave above the fundamental) can be at +4 cents. > > These observations provide an ample hypothesis for tuner > instability, but unfortunately suggest no solution. > > > > To get on or off this list see list information at > http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html > the next auto-quote is: True virtue is life under the direction of reason. (Baruch Spinoza) /\/\ Peter Nightingale Telephone (401) 874-5882 Department of Physics, East Hall Fax (401) 874-2380 University of Rhode Island Kingston, RI 02881
