Pianotech

Far greater high partial information, spectral purity, and tuning accuracy is achieved with sensor vs mic. This indeed affects the tuning accuracy measurement achievable in an ETD app. The PianoSens sensor captures far more energy in the higher partials or harmonics. This results in a greater signal-to-noise of the waveform, and therefore more accuracy in the frequencies. In this example, the difference is as much as 0.6 cents but on some notes it can be greater than 1 cent.
YouTube video below.

Low Frequency Spectra: PianoSens vs Microphone

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Steven Norsworthy
Cardiff By The Sea CA
(619) 964-0101
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Hi, I've got a question about the noted frequency difference you're observing that hopefully you can clear up for me. The improved signal is helpful for the ETD to determine the frequency (esp in noisy conditions), but I wonder if the frequency difference could also be from picking a different partial to measure from. If the relative partial strengths are causing it to favor or weight the frequency results differently? Do you know how this works in different ETDs? I assume the computed pitch is reversed from the inharmonicity model and the observed partial frequency. Given the inexact nature of iH models, I suppose you would get slightly different pitches based on which partial was used. You could minimize the error, take an average, etc. Maybe ETDs use all the frequencies at once to measure the pitch? 

Thank you, 

Joshua

Most of the app-based ETD's use all of the partials to calculate the frequency target.  Or at least as many as they want to use, not just one.  For example, if you want to change from a 6:3 octave to a 4:2 octave, the ETD can calculate a smooth transition using the measured partials.  Same with changing octaves to 12th tuning, etc.  Many app-based ETD's can give you options to choose what "style" of tuning you want.  With a single partial, this can't be done as accurately or as smoothly.  That's why measuring the partials as accurately as possible is crucial.  If one or more are not measured accurately, or it's not detected, it will skew the calculation.  Then there is the point of measuring the pitch.  When you play a string, the pitch slightly changes from the attack to the decay period.  When is the proper time to decide if you're on target?  Most ETD's just show the decay phase, and there's no predetermined way to lock in the measurement in a time period after the attack.  That's important, because no matter how accurate the ETD calculation is, you have to be consistent to measure during a finite time window.  Waiting to read the target indicator for more than a second or two will give a flatter indication than if you take it earlier.  Pianoscope is the only app that has that capability.  Putting the sensor and Pianoscope together is the best combination for tuning accuracy.  I wish that the other ETD's include the freeze feature to improve their accuracy too.