I'd be interested to know what goes into an ETD's interpretation of a false beat. Does the FFT really include such drastically different frequencies as a single digit Hz range, and why would the FFT think a 3p/s, clearly unrelated to the note's partial series.
Yes the side-by-side comparison of what the acoustic mic and your sensor are giving the FFT is impressive. But you then describe the software as saying that the (irrelevant) beat is there because 1.) there exists a combination of two separate tones which created it and we'll derive our frequency by smear them for an average. I'll admit that does sound sloppy. Do all ETDs do this? (That is, infer two separate tones, instead of it being a single tone which also happens to have a much slower slow disturbance pattern for mechanical reasons.)
Of course, I always imagined that there was a healthy amount statistical smoothing to eliminate the jittering of an ETD's display. I don't know whether what these ETDs show us are precise calculations, or whether what we're looking at is the most likely best pick of a probability field.
However ETDs do this, my main concern was the idea that the best that either ETD or ear can do will have the same level of imperfection at the end. I worry that the OP might have been hoping that an ETD could make the result of a well-tuned ETD unison a step above the aural unison.
Original Message:
Sent: 01-13-2024 21:11
From: Steven Norsworthy
Subject: False Beats: Two Origins: Acoustic vs Mechanical
I put great effort into that YouTube video lecture on False Beats today. It would be great to get some definitive feedback on it. Thanks!
https://youtu.be/e_UvfoUevy8
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Steven Norsworthy
Cardiff By The Sea CA
(619) 964-0101
Original Message:
Sent: 01-13-2024 20:59
From: Bill Ballard
Subject: False Beats: Two Origins: Acoustic vs Mechanical
Actually, I believe that any ETD will have a definite advantage over our own ears. False beats (in the beats/sec range that we can hear) are actually an AM-modulation of the the sound coming off that string. If we're tuning A6 aurally, and if there's a 5 b/s false beat, we hear both that and the 1772 Hz fundamental. If the ETD is doing the tuning, then at that point in the tuning pattern, it's only paying attention to something in the neighborhood of 1771 Hz (± 50 Hz). For it, the 5 b/s false beat is well off its radar.
And yes, false beats are annoying during aural unison tuning. If only one of the strings on that note is false bearing, we're in luck. We simply tune those two non-beating unisons to themselves, and, that done, tune the false beater paying attention only to the beat rate which is moving. This is tricky because both the moving and stationary are in the same range and can be confused. But in the end, you'll know the unison is done because 1.) the only beat to be heard in the false one, and 2.) the complete amplitude of the false beat has been reduced reduced from 100% (when listening only to the false beating string) to 33% (when that string is added to its non-beating partners). So, while we don't pay attention to the false beater's reaction to our tuning of it, it's good to recognize that beat rate when it shows up as the final imperfection in our unison.
Things aren't that much more complicated when there is only one non-beater in that trichord. You tune each beater, separately, to the non-beater, and in the addition of sound waves, the sum of these AM-modulated beats will still amount to only 1/3 of the volume. (…except where both beaters have the identical b/s speed, in which case they will reinforce each other and overpower the non-beater's volume.)
And when all three strings are beaters, that's when you thank the existence of ETDs. But still, we should recognize that while EDTs can ignore beat rates, their best work will still be no different from our best aural work. If we're bothered by traces of false beats in the final tuning, they will be there no matter if tuned by ear of ETD. ETDs have no better chance of making a false beat disappear than a skilled aural tuner.
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William Ballard RPT
WBPS
Saxtons River VT
802-869-9107
"Our lives contain a thousand springs
and dies if one be gone
Strange that a harp of a thousand strings
should keep in tune so long."
...........Dr. Watts, "The Continental Harmony,1774
Original Message:
Sent: 01-13-2024 17:35
From: Peter Grey
Subject: False Beats: Two Origins: Acoustic vs Mechanical
We all work hard at IGNORING these false beats so that we can tune the REAL beat. If this device is capable of reducing or even eliminating some of this annoying "noise" I'm all for it. I really don't care precisely where they're coming from. I want to reduce their interference if possible. I'm looking forward to actually trying the thing soon.
And anyway, we all know that we can overpower some of these "false" beats with careful unison tuning, and they "magically" disappear.
Peter Grey Piano Doctor
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Peter Grey
Stratham NH
(603) 686-2395
pianodoctor57@gmail.com
Original Message:
Sent: 01-13-2024 16:04
From: Steven Norsworthy
Subject: False Beats: Two Origins: Acoustic vs Mechanical
'The Rub,' as you say, is that you can easily hear it. I'll post the audio of both. Of course you can hear that difference in the two waveforms. So, as a 'diagnostician' how do you try to fix that false beat if you don't know where it is coming from? As a teacher, I am probably the first one (that I know of) who has discovered that there are two sources of false beats. Do you not want me to teach or publish a finding like that? And as far as your tuning goes, which one of those peaks are you going to tune to? That is a rhetorical question, of course.
I make the same offer to you, that you ask your local PTG president to schedule me for a zoom class like I am doing across the country. You can talk to Eliot Lee, the president of the PTG in Phoenix, as a reference. I just did a class for them. They were 'very receptive.'
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Steven Norsworthy
Cardiff By The Sea CA
(619) 964-0101
Original Message:
Sent: 01-13-2024 15:26
From: Steven Rosenthal
Subject: False Beats: Two Origins: Acoustic vs Mechanical
Steve, here's the rub. If you can't "hear" it, you can't adjust for it. There are small adjustments that can be made to mitigate unfavorable sounds, simply ignoring them might get you close but a good tuner can do better with their ears. The sensor doesn't pick up what could be glaring problems. This is an example of what seems to me an apparent contradiction. If you're not factoring in the perturbations created by the soundboard then you can't adjust for them. Perhaps this doesn't matter, but that is yet to be demonstrated.
A video that takes just the middle strings (using a temperament strip) that lays in a temperament and tunes from E3 to C5 and is then run through and satisfies the standard aural interval checks would allay these misgivings.
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Steven Rosenthal RPT
Honolulu HI
(808) 521-7129
Original Message:
Sent: 01-13-2024 01:33
From: Steven Norsworthy
Subject: False Beats: Two Origins: Acoustic vs Mechanical
You will not find this in the literature. It is from my research. I teach this in my class lectures.
There are two independent sources of false beats:
1) Acoustical (interference and resonances from other parts and strings of the piano)
2) Mechanical (in the string, differences in the vertical minus horizontal frequencies inherent in the string movement).
The sensor does not 'hear' the acoustic false beat so it enables you to zero in on the mechanical false beat in the string under test.
Here is a picture from an actual parallel recording, one with sensor and one with mic.
Below that is a view of the spectra going on. Notice the false beat close to the actual desired frequency.
Regards,
Prof. Steve
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Steven Norsworthy
Cardiff By The Sea CA
(619) 964-0101
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