WOW! James Grebe R.P.T. from St. Louis pianoman@inlink.com "Only my best is good enough" ---------- > From: Robert Scott <rscott@wwnet.com> > To: pianotech@ptg.org > Subject: How accurate are inharmonicity measurements? > Date: Monday, November 03, 1997 11:53 AM > > To those with visual tuning devices: > > I would like to confirm some research I have been doing on > measurement of inharmonicity for the TuneLab97 program. A few > months ago Jim Coleman, Sr. and I had some exchanges on this list > regarding the issue of how voicing might affect inharmonicity. > While that particular question may have been left undecided, the > more general question that interested me was "How accurately can you > measure inharmonicity anyhow?" A related question is "How > accurately do you need to measure inharmonicity in order to use > those measurements to construct good tunings?" > > Although I have not had personal experience with either the SAT or > the RCT, I gather that the operation of these two devices is > different regarding the measurement of inharmonicity. It seems that > the SAT relies on the tuner to push buttons to stop the display. > The RCT, on the other hand, "listens" for a period of time and then > automatically makes calculations of all significant partials. It > seems that each of these methods has its own advantages. The > automatic method is obviously more convenient for the tuner, since > only one sound sample needs to be taken and the computer calculates > all partials from that sample. But false beats can confuse such > algorithms, making the measurement unreliable. (I have heard that > the RCT detects this condition and warns the tuner to take a better > sound sample.) With the more manual method used in the SAT, the > tuner has the opportunity to see the irregular movement of the > lights caused by false beats and either pick another string or use > his judgement about when the lights are the closest to being > "stopped". My question is, which of the two methods is most > reliable on the average. > > I have attempted to implement the automatic method in the next > version of the TuneLab97 program and have gotten mixed results. It > seems that when I pick very good and stable strings (no false > beats), I get excellent repeatability in the inharmonicity > measurements. My measurements are based on a 3 second sound sample. > But when I try to measure strings with a little wobble in them, the > inharmonicity measurements are more variable. The following > repeated inharmonicity measurements were made. The notes and the > partials that I selected just happen to correspond to the FAC > measurements in order to make it easy to compare my measurements to > SAT measurements. The measurements were made on a Kawai 650. > > > Note 2nd 3rd 4th 5th 6th 7th 8th 8th-4th > --- ---- ---- ---- ---- ---- ---- ---- ------- > F3 -0.42 1.25 2.20 3.20 4.45 5.89 8.01 5.81 > F3 -0.23 1.30 2.06 3.22 4.46 5.86 7.95 5.89 > F3 -0.45 1.29 1.98 3.23 4.44 5.82 7.92 5.94 > F3 -0.38 1.33 2.04 3.32 4.46 5.88 7.94 5.90 > F3 -0.41 1.25 1.99 3.32 4.40 5.86 7.91 5.92 > F3 -0.19 1.33 2.03 3.33 4.44 5.89 7.93 5.90 > F3 -0.19 1.34 2.01 3.33 4.42 5.89 7.95 5.94 > F3 -0.28 1.29 1.89 3.22 4.34 5.79 7.93 6.04 > ...a different unison:.... > F3 0.64 1.84 2.38 3.72 5.11 6.78 7.97 5.59 > F3 0.63 1.80 2.37 3.70 5.07 6.74 8.65 6.28 > F3 0.63 1.79 2.37 3.69 5.08 6.73 8.02 5.65 > F3 0.64 1.73 2.38 3.67 5.08 6.67 8.61 6.23 > F3 0.65 1.84 2.39 3.73 5.11 6.78 8.02 5.63 > F3 0.56 1.67 2.30 3.61 4.96 6.61 8.55 6.25 > > Note 2nd 3rd 4th 4th-2nd > --- ---- ---- ---- ------- > A4 1.20 3.27 6.72 5.52 > A4 1.12 3.27 6.74 5.62 > A4 1.11 3.24 6.72 5.61 > A4 1.22 3.36 6.88 5.66 > A4 1.00 3.19 6.73 5.73 > A4 1.34 3.58 7.00 5.66 > A4 1.31 3.69 6.99 5.68 > > Note 2nd > --- ---- > C6 3.34 > C6 3.23 > C6 2.86 > C6 2.55 > C6 2.26 > C6 2.80 > ..a different unison:... > C6 5.95 > C6 6.00 > C6 6.55 > C6 6.15 > C6 5.81 > > I would appreciate any confirming or contradicting information on > this subject. In particular, I would like to know how much > variation there would be if two or three different tuners measured > the FAC numbers on the same piano. I want to know how much a factor > individual judgement plays when strings are less than perfect. > > Bob Scott > Ann Arbor, Michigan > (Detroit-Windsor PTG) > >
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