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How does a violin reproduce overtones? - Theorizing a model


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1 hour ago, Marty Kasprzyk said:

I didn't say note evenness was the only measure--I said "One objective measure..."

Note loudness unevenness is quite common (see attachment) even in great instruments.  

Screen Shot 2021-05-16 at 9.44.43 AM.png

I have a copy of these books. The text about these Strads reads: Five of these were made by Stradivari in the years from 1684 to 1721, the last three (Nos 16, 19, 20) having the characteristic flat model, the other two (nos 21 and 22) being higher, and somewhat like an Amati. 

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Maybe we can figure out which of the Saunders curves are the Titian from this plot? The black line is the sweep response of a bronze string driven vertically, from 1940 by Saunders. The red curve is Joe Curtin impact hammer rig measurement of the same instrument in 2007 horizontally, I guess. Maybe an average 360 degrees around it.

130202ComparisonofSaunders1940spectrumand2007bigger.jpg

Edited by Anders Buen
Corrected year.
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24 minutes ago, Anders Buen said:

Yes! Where did you find this? Or have you made it yourself?

I calculated it myself from the definition of a decibel:   dB= 20log1/n,

but I found the same thing  (attachment) in a text book: "Introduction to Sound"  3rd edition, 1999 by Charles E. Speaks which discusses saw tooth waves.

 

 

Scan.jpeg

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11 minutes ago, Marty Kasprzyk said:

I calculated it myself from the definition of a decibel:   dB= 20log1/n,

but I found the same thing  (attachment) in a text book: "Introduction to Sound"  3rd edition, 1999 by Charles E. Speaks which discusses saw tooth waves.

 

 

Scan.jpeg

Thanks, Marty! 

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2 hours ago, Anders Buen said:

Maybe we can figure out which of the Saunders curves are the Titian from this plot? The black line is the sweep response of a bronze string driven vertically, from 1940 by Saunders. The red curve is Joe Curtin impact hammer rig measurement of the same instrument in 2007 horizontally, I guess. Maybe an average 360 degrees around it.

130202ComparisonofSaunders1940spectrumand2007bigger.jpg

We can't. I can stage the black or the red lines on the same violin or any of my violins in my cabinet

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Regarding impact spectrum ala Curtin way, you won't get repeatable result if you don't use a real-time FFT and adjust your rig according to a baseline. The angle, hardness of the hammer, material of the hammer, speed, weight, shape of the bridge tip, shape of the hammer, angle of the impact,  properties of the hammer etc. etc.....

IT IS SUPER SENSITIVE!

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7 minutes ago, David Beard said:

One basic thing I'm curious to know is how much energy is lost between bowing input and radiated sound/signal output?

I think Cremer tried to estimate this. If I recall correctly is was about 4%. I may look that up tomorrow. The number is correct. He say only 0,4% per cycle is radiated as sound. Thank God, our ears are very sensitive.

Edited by Anders Buen
Added check up, and a little more text
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42 minutes ago, Peter K-G said:

Regarding impact spectrum ala Curtin way, you won't get repeatable result if you don't use a real-time FFT and adjust your rig according to a baseline. The angle, hardness of the hammer, material of the hammer, speed, weight, shape of the bridge tip, shape of the hammer, angle of the impact,  properties of the hammer etc. etc.....

IT IS SUPER SENSITIVE!

The impact force is measured, and Joe use a flat tip semi hard plastic tip, hard enough to provide sufficient high frequency energy. The sensors could have been 3-axis, but that may come in the future.

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21 minutes ago, Anders Buen said:

I think Cremer tried to estimate this. If I recall correctly is was about 4%. I may look that up tomorrow. The number is correct. He say only 0,4% per cycle is radiated as sound. Thank God, our ears are very sensitive.

That seems very low.  Much lower than I imagined.

I guess there are several points where it would be interesting to know power levels.

There is the arm waving to move the bow. That has a power level.

There is the transfer of enegry from the bow contact into string vibrations.  That has a power level.

Then there is the energy transfer from bridge feet into the violin.

And at a later pointed there is the energy radiating as sound.

If the overall drop is 96%, most of the loss must be at the bow arm to string transfer.

There can't be too much energy lost later, as there aren't any heat issues with violin playing.

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28 minutes ago, Anders Buen said:

The impact force is measured, and Joe use a flat tip semi hard plastic tip, hard enough to provide sufficient high frequency energy. The sensors could have been 3-axis, but that may come in the future.

Joe, is the impact hammer master!

When I was young I worked at a gas station and the Payazzo was popular https://en.wikipedia.org/wiki/Payazzo

I don't know what these are called in English https://sv.wikipedia.org/wiki/Brytarspets

I changed a lot of them at my work and it got me thinking...

I made a rig of them and was able to empty these Payazzos of all the money.

Didn't take any money though, put them all back, but I could have made a fortune!

Repeatability!

 

 

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3 hours ago, Anders Buen said:

I think Cremer tried to estimate this. If I recall correctly is was about 4%. I may look that up tomorrow. The number is correct. He say only 0,4% per cycle is radiated as sound. Thank God, our ears are very sensitive.

I read that too.  But I freely admit I'm not smart enough to understand Cremer (1). My understanding is that the wood plates are way too heavy to have a good conversion of bowing arm motion energy into sound.  A clue is that plucking a banjo string with its light thin stretched skin top is much louder than a guitar with its much heavier wooden plate top.

The loudest bowed sound I ever made was bowing a banjo.  Banjo has a flat bridge and a round shaped so you can only bow the outer strings.

Another clue is that many  drums use light weight stretch skins rather than  thicker and heavier wooden plates.  At the risk of oversimplification if  you believe in Newton's first law  F=ma where F is force, m is mass, and a is acceleration then a= F/m.
So the string forces F through the bridge on the top plate produce more acceleration of a top plate if its mass m is low. This higher plate acceleration produces more air movement next to the plate hence louder sound (2). Thus the top plate's mass should be low which goes along with Joseph Curtin's comments about Carleen Hutchin's advice(3) 

"I never thought about weighting  plate until Hutchins  suggested it in 1986.  Five years later, Gregg Alf and I had the top off a 1716 Stradivari violin, and what struck me was how light it was-54g without bass-bar..."

 

1.   Lothar Cremer, "The Physics of the Violin", translated by John S.Allen, MIT Press 1984. chapter  II  the body of the instrument, 9 'The bridge', p 203

2.  Marty kasprzyk after one bottle of home-made wine.

3.   "Tap Routine" in the October 2006  'The Strad'.

 

 

 

 

s:

"

 

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4 hours ago, David Beard said:

If the overall drop is 96%, most of the loss must be at the bow arm to string transfer.

What about the vibrating neck which doesn't produce sound?

I wonder too how this compares to other music instruments. Maybe there is, for what reason ever, always a big energy loss factor.

 

 

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4 minutes ago, Marty Kasprzyk said:

Another clue is that many  drums use light weight stretch skins rather than  thicker and heavier wooden plates.  At the risk of oversimplification if  you believe in Newton's first law  F=ma where F is force, m is mass, and a is acceleration then a= F/m.
So the string forces F through the bridge on the top plate produce more acceleration of a top plate if its mass m is low. This higher plate acceleration produces more air movement next to the plate hence louder sound (2). Thus the top plate's mass should be low which goes along with Joseph Curtin's comments about Carleen Hutchin's advice(3) 

"I never thought about weighting  plate until Hutchins  suggested it in 1986.  Five years later, Gregg Alf and I had the top off a 1716 Stradivari violin, and what struck me was how light it was-54g without bass-bar..."

That's what I am more and more thinking about. Try to imagine the top of a violin as a drumskin. So the lighter and thinner the better. But this requires alterations to the rest of the body. I think building a rigid frame around the top plate to make it work acoustically confirms this idea pretty well. 

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14 minutes ago, Andreas Preuss said:

That's what I am more and more thinking about. Try to imagine the top of a violin as a drumskin. So the lighter and thinner the better. But this requires alterations to the rest of the body. I think building a rigid frame around the top plate to make it work acoustically confirms this idea pretty well. 

Yes lightness is really good for increasing sound output but the limitation is the emergence of bad wolf notes.    Single high amplitude peaks in the frequency response curves should be decreased either through damping and/or splitting into smaller amplitude ones by coupling onto some other vibrating part (fingerboard, tail piece, or the player's inflated head). 

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1 hour ago, Andreas Preuss said:

What about the vibrating neck which doesn't produce sound?

I wonder too how this compares to other music instruments. Maybe there is, for what reason ever, always a big energy loss factor.

 

 

Vibration itself isn't loss.  It's dampening in to heat that is loss, and radiation of as sound also.

Most vibrations, like the neck, will  cycling through the instrument until dissipated as either sound/noise radition or heat. I can't think of any other dissipations for a violin.

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temperature v heat

volts v current

water speed v flow

*******

Sound is a transfer of energy as vibrations.    Like the energy transfers above, there is also an aspect of the 'heft' of what is happening.

With heat, we talk of temperature, but also thermal mass.

With vibrations, there is a similar aspect, though we don't seem to have ready language to address it.

The energy in vibration is not just about the amplitude of the vibration, but also about the mass that is in motion.  More mass moved at the same speed/amplitude holds greater energy.

Yes, thin light plates will swing more for equal energy.  But heavier plates brought into equal motion will hold more energy.  And will have more capacity to radiate energy.

 

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On 5/28/2021 at 4:58 PM, Rothwein said:

Using an online tone generator I found:

https://www.szynalski.com/tone-generator/

pure sine waves are less audible (to me, anyway) at higher frequencies (above 10000Hz) than the synthesized sawtooth waves. There is a sum of a LOT of something in the “violin sound wave.“

Does a sawtooth wave at 440Hz also contain all the upper partial tones?

Using this generator, using only "ones" computer speakers {no external ones} I wonder what "numbers" "we" all come up with as far as range,  I suggest this as regardless of what the "numbers" are in all the spectral graphic data there is what we hear, and again I wonder if "we" are all hearing the same thing....so using just my speakers onboard my somewhat crappy old laptop my range is

39 to about 11,000

and "yours is?"

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