JohnRoberts said:
Thanks...Cjuried said:
JohnRoberts said:Thanks...Cjuried said:
If you really want to know I will tell you more than you want to know about drum tuning (or what they call "tuning").
First I had to look up LM567.. an old PLL... (phase locked loop)... Not an obvious choice for note sniffing (hitting the drum and trying to pick out note resonances), but i guess it might be made to work...
=====
Not to change the subject but back in the 70s, Dr Patronis a well known physicist from Ga Tech invented a feedback finder/killer based on using a bank of spaced PLL to identify feedback frequencies and then use the PLL outputs to turn on fixed notch filters, to suppress that feedback. This was way ahead of it's time and very slick technology for 40 years ago.. I brought him into Peavey and tried to work out a deal with him to let Peavey make them but there were legal entanglements with another licensee of his so it didn't happen..
======
OK back to drum tuning... Drums are difficult because when you strike the drumhead they make more than one pitch (see http://circularscience.com/about-drums for TMI about drums). So any sniffer has to selectively focus on just one of the sundry note pitches (you obviously can't tune non-harmonic overtones onto a single note). As if that isn't difficult enough, striking the drumhead actually bends the note pitch (sharp momentarily) until the head relaxes again. How hard you strike alters the sound envelope.
So while you might be able to make a PLL based sniffer recognized pre-arranged targets, to read the actual drumhead tuning requires tweaking the PLL frequency centers on the fly.
ASSuming you could reliably sniff and adjust the notes from striking the drumhead (I don't), my tuner adds an additional step after you have already dialed in the drum to a desired note pitch. Using that fixed frequency I set up a standing wave in the drumhead at resonance mode (1,1) and read the time delay, or phase shift between that standing wave relative to the exciting sine wave coming from my tuner. From this phase information I can isolate and accurately measure the relative impact of each individual lug tension. When every lug is adjusted to deliver the exact same phase shift, the drum is "clear".
"Clear" is a vague drum term that describes a more pure open sound. The drum still makes the multiple non-harmonic overtones, but just the simplest single series of overtones, not a dissonant hodge-podge of multiple closely spaced but not the same pitch overtones. Even this explanation is not very satisfying.
While i don't expect anyone to just take my word for it, here is a link to a recent discussion on a drum forum http://www.drummerworld.com/forums/showthread.php?t=127692 Where several users chimed in.
I apologize for this veer into blatant self promotion, and now return you to your original programming .
To answer the question using PLL is probably not cheaper than performing a FFT inside a microprocessor. While the micro is more expensive than one PLL you would need a micro to tweak the PLL to extract pitch, so easier to just perform a FFT like the cheap note sniffers do (instead of sweeps like I do).
JR
PS: for more info about my tuner US Patent # 6,925,880 for Patronis PLL based feedback killer US patent # 4,079,199 (1977)
Perhaps(?) Sabine is located in FL IIRC and Patronis is well known in the industry.Cjuried said:JohnRoberts said:Thanks...Cjuried said:
If you really want to know I will tell you more than you want to know about drum tuning (or what they call "tuning").
First I had to look up LM567.. an old PLL... (phase locked loop)... Not an obvious choice for note sniffing (hitting the drum and trying to pick out note resonances), but i guess it might be made to work...
=====
Not to change the subject but back in the 70s, Dr Patronis a well known physicist from Ga Tech invented a feedback finder/killer based on using a bank of spaced PLL to identify feedback frequencies and then use the PLL outputs to turn on fixed notch filters, to suppress that feedback. This was way ahead of it's time and very slick technology for 40 years ago.. I brought him into Peavey and tried to work out a deal with him to let Peavey make them but there were legal entanglements with another licensee of his so it didn't happen..
======
OK back to drum tuning... Drums are difficult because when you strike the drumhead they make more than one pitch (see http://circularscience.com/about-drums for TMI about drums). So any sniffer has to selectively focus on just one of the sundry note pitches (you obviously can't tune non-harmonic overtones onto a single note). As if that isn't difficult enough, striking the drumhead actually bends the note pitch (sharp momentarily) until the head relaxes again. How hard you strike alters the sound envelope.
So while you might be able to make a PLL based sniffer recognized pre-arranged targets, to read the actual drumhead tuning requires tweaking the PLL frequency centers on the fly.
ASSuming you could reliably sniff and adjust the notes from striking the drumhead (I don't), my tuner adds an additional step after you have already dialed in the drum to a desired note pitch. Using that fixed frequency I set up a standing wave in the drumhead at resonance mode (1,1) and read the time delay, or phase shift between that standing wave relative to the exciting sine wave coming from my tuner. From this phase information I can isolate and accurately measure the relative impact of each individual lug tension. When every lug is adjusted to deliver the exact same phase shift, the drum is "clear".
"Clear" is a vague drum term that describes a more pure open sound. The drum still makes the multiple non-harmonic overtones, but just the simplest single series of overtones, not a dissonant hodge-podge of multiple closely spaced but not the same pitch overtones. Even this explanation is not very satisfying.
While i don't expect anyone to just take my word for it, here is a link to a recent discussion on a drum forum http://www.drummerworld.com/forums/showthread.php?t=127692 Where several users chimed in.
I apologize for this veer into blatant self promotion, and now return you to your original programming .
To answer the question using PLL is probably not cheaper than performing a FFT inside a microprocessor. While the micro is more expensive than one PLL you would need a micro to tweak the PLL to extract pitch, so easier to just perform a FFT like the cheap note sniffers do (instead of sweeps like I do).
JR
PS: for more info about my tuner US Patent # 6,925,880 for Patronis PLL based feedback killer US patent # 4,079,199 (1977)
I suspect that Dr. Patronis' work had a direct impact on the design of the Sabine "Feedback Exterminators" of the late 1980s's / early 1990's. Interesting read, indeed. While reading Dr. Patronis' patent I was reminded of the "Surface acoustic wave oscillator", found here: http://patents.justia.com/patent/4871984 . Where the key lies in detecting an offending frequency in which the "overall phase shift is an integral multiple of 2pi radians" with a loop gain => 1.
JohnRoberts said:Perhaps(?) Sabine is located in FL IIRC and Patronis is well known in the industry.Cjuried said:JohnRoberts said:Thanks...Cjuried said:
If you really want to know I will tell you more than you want to know about drum tuning (or what they call "tuning").
First I had to look up LM567.. an old PLL... (phase locked loop)... Not an obvious choice for note sniffing (hitting the drum and trying to pick out note resonances), but i guess it might be made to work...
=====
Not to change the subject but back in the 70s, Dr Patronis a well known physicist from Ga Tech invented a feedback finder/killer based on using a bank of spaced PLL to identify feedback frequencies and then use the PLL outputs to turn on fixed notch filters, to suppress that feedback. This was way ahead of it's time and very slick technology for 40 years ago.. I brought him into Peavey and tried to work out a deal with him to let Peavey make them but there were legal entanglements with another licensee of his so it didn't happen..
======
OK back to drum tuning... Drums are difficult because when you strike the drumhead they make more than one pitch (see http://circularscience.com/about-drums for TMI about drums). So any sniffer has to selectively focus on just one of the sundry note pitches (you obviously can't tune non-harmonic overtones onto a single note). As if that isn't difficult enough, striking the drumhead actually bends the note pitch (sharp momentarily) until the head relaxes again. How hard you strike alters the sound envelope.
So while you might be able to make a PLL based sniffer recognized pre-arranged targets, to read the actual drumhead tuning requires tweaking the PLL frequency centers on the fly.
ASSuming you could reliably sniff and adjust the notes from striking the drumhead (I don't), my tuner adds an additional step after you have already dialed in the drum to a desired note pitch. Using that fixed frequency I set up a standing wave in the drumhead at resonance mode (1,1) and read the time delay, or phase shift between that standing wave relative to the exciting sine wave coming from my tuner. From this phase information I can isolate and accurately measure the relative impact of each individual lug tension. When every lug is adjusted to deliver the exact same phase shift, the drum is "clear".
"Clear" is a vague drum term that describes a more pure open sound. The drum still makes the multiple non-harmonic overtones, but just the simplest single series of overtones, not a dissonant hodge-podge of multiple closely spaced but not the same pitch overtones. Even this explanation is not very satisfying.
While i don't expect anyone to just take my word for it, here is a link to a recent discussion on a drum forum http://www.drummerworld.com/forums/showthread.php?t=127692 Where several users chimed in.
I apologize for this veer into blatant self promotion, and now return you to your original programming .
To answer the question using PLL is probably not cheaper than performing a FFT inside a microprocessor. While the micro is more expensive than one PLL you would need a micro to tweak the PLL to extract pitch, so easier to just perform a FFT like the cheap note sniffers do (instead of sweeps like I do).
JR
PS: for more info about my tuner US Patent # 6,925,880 for Patronis PLL based feedback killer US patent # 4,079,199 (1977)
I suspect that Dr. Patronis' work had a direct impact on the design of the Sabine "Feedback Exterminators" of the late 1980s's / early 1990's. Interesting read, indeed. While reading Dr. Patronis' patent I was reminded of the "Surface acoustic wave oscillator", found here: http://patents.justia.com/patent/4871984 . Where the key lies in detecting an offending frequency in which the "overall phase shift is an integral multiple of 2pi radians" with a loop gain => 1.
AFAIK the Sabine uses DSP probably a FFT and then some post processing to discriminate between musical tones and feedback tones. Then applying notch filters as needed to suppress feedback.
It is not trivial to discern feedback from music, and one common approach is to look at the envelope of the tone. Musical notes generally decay naturally after some initial attack, while feedback modes start small and build louder.
JR
. Second, is the correlation between measuring loudspeaker current consumption changes versus the proximity of a loudspeaker to that of a drumhead. This is a quantifiable measurement that I had not thought of in the past.
Ok that's another strategy to parse feedback tones from music. Most (not all***) musical notes consists of complex combinations involving multiple harmonic overtones (same note in different octaves). Feedback tones are generally simple sine waves, so lack the typical harmonic content (clever).Cjuried said:
I talk about this on my About drums page. http://circularscience.com/about-drums. The issue is that the vibration modes involve different paths across, and around the "round" drum head. Round is the operative term as we know from basic algebra there is a pi term between diameter and circumference of a round drumhead, this 3.1415x term makes for less than neat math between overtones. If that wasn't bad enough, when you mount a second drum head, the relative mass and tension of both interact to affect one series resonances but not the other, so there can be a near infinite number of different voicing possibilities from relative and absolute tension.
Actually in my judgement tuning a drum to specific notes is less important than tuning it to itself (clear quality), but I may be biased. I provide note information because it falls out of my digital microprocessor approach for almost free.I can imagine, for accurate and precise tuning, this takes some serious work, which is were your "Resotune" really hits the drum on the head
When writing a patent you throw in all the alternate approaches you can think of, basically to prevent somebody else from patenting that and preventing you from using it. My intent was to look at using the speaker current draw to replace using a microphone (first version used two mics) to identify drumhead resonances. In theory at a resonant frequency it will be easier for the speaker to push air up and down. Indeed there was some there there, but not enough current change to reliably identify multiple drumhead resonances.
I have not pursued this personally but IIRC there was a commercial tympani tuning product that used light to sniff head vibration.
JohnRoberts said:
What the hell... If I was serious I would have built one by now, and who knows it might not work, but like many things I've been paying attention to sound for a few years now too...Gene Pink said:
Yes that is actually a pretty old idea (70s?). Instead of a fixed pitch shift, more like a chorus up and down will break up the feedback build, but still causes an unnatural oddly pitched reverb decay. Because of that it was mainly relegated to low-fi speech only applications.
Yup, good monitors, good mics (with right pattern ) and proper set up will deliver all the SPL most stages need.
PRR said:
PRR said:
I wish he was more specific (academic curiosity, not commercial). Find a better reference. I am familiar with Dr Francis Lee's ( MIT Professor) varispeech.. It was our, VSC corp's (Variable Speech Control's) major competitor back in the early '70s. While his was the digital 8-bitter I alluded to earlier (ours was analog). He shifted pitch both up and down, while the larger application was speeding up tapes and restoring the pitch by shifting it down for blind talking book users,( library of congress money yadda yadda), there was a smaller fraction interested in slowing down tapes for learning new language pronunciations. Another hypothetical application was slowing down too fast musical (guitar) passages to help novice players learn how to play them, but the sound quality was too warbley (a technical term) to gain much interest. Speaking of Warbly, I will occasionally hear some late night movie background music where some sharp pencil type has applied old school time "compression" (presenting same program in less time by speeding up and restoring pitch), so they could squeeze in a few extra commercials. The tell is hearing a burbling sound on dense orchestral passages. Something I'd love to unlearn. 8)
I'm repeating myself, but i already said I am not pursuing this... I introduced Dr Patronis to Hartley around 30 years ago, and I am all too familiar with Peavey's own DSP based feedback killers some 20 years ago. I have better things to do than wrestle with MI pigs in the mud.
