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Marty Kasprzyk

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Everything posted by Marty Kasprzyk

  1. The Chinese erhu uses a membrane of python skin and it sounds better than many violins.
  2. The bowed string produces a sawtooth wave. You can hear one through your computer's speaker at https://onlinetonegenerator.com If your speaker is lousy with lots of big resonance peaks and deep valleys in its frequency response curve you might get a sound like a violin's. If your speaker is really bad it might sound like a Strad.
  3. 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).
  4. 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: "
  5. 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.
  6. I don't know. The loudness graph is from Saunders' 1937 report: F. A. Saunders, "The Mechanical Action of violins", J. Acoust. Soc. Amer., 9, 81-98 (Oct 1937) reprinted in Musical Acoustics, Part I, Benchmark Papers in Acoustics/5, 1975 I loaned my Benchmark book to a friend so I can't see if Saunders used the 1715 Titian in this graph. But I do know he measured the Titian later in 1946:
  7. 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.
  8. One objective measure of violin quality is the evenness of the all of the note's loudness. Some players go up and down the chromatic scale or play music passages to find overly loud or weak notes which are generally not liked. The loudness of each note can also be measured with a sound meter.
  9. A perfect saw tooth wave has all of the overtones. A triangular wave has only the odd numbered ones
  10. Yes that is beautiful but I still think you should use wood that naturally has that color.
  11. I still agree with Jim that natural color looks best. I scraped off all the finish on the Chris Andrew violin that Rue had shown us and revarnished it without any yellow color stain or varnish to reveal its natural wood colors as seen in the attached photo. I hope Chris Andrew has a sense of humor.
  12. Hi Anders, I bowed the G string very close to the bridge by tilting the bow so that only a narrow band of hair touched the string. If I used very little bow force I was able to get the bow to slide across the string without producing the G note--all I got was the same kind of noise that bowing on the bridge edge produced. ApparentlyI was using a bow force below the "minimum bow force" line in Schelleng's famous bow force vs. bow-to-bridge distance diagram. The noise again had some higher peaks at the A0 frequency like Peter had found but the peaks were randomly spaced again. So I think you're right in thinking noice comes from the fly back slip phase in the bow/string interaction. The video David Burgess gave us shows the bow hair stays in contact with the string. I wonder if good and bad violins have different signal to noise ratios.
  13. I'm quite sure the noise between a note's harmonics are produced by the bow hair. Attached is a plot up to 8000Hz of a bowed violin open G string as a blue line. Also plotted is an orange line showing the bowing of the violin bridge upper bass side edge which produces a "hissy" kind of white noise. The violin body/bridge filters the bow noise just like it filters the string harmonics of a note and the orange line of the bowed bridge edge follows the same envelope shape as the noise of the bowed note. Also attached is the same plot going up to only 600Hz. The A0 resonance peak (~280Hz) shows up as noise just like Peter had found. All violins probably do the same thing.
  14. Put it into smaller and smaller bottles to limit the air space. Excessive air exposure often badly affects wine and some people do purge partially empty bottles of wine with inert gases. Although these gas purging devices and their small gas cylinders are relatively inexpensive I have found it is better to simply drink all of the wine in the bottle.
  15. The violin body is not an amplifier--it is an energy transducer. It converts the vibrating energy of the string into the vibrating energy of the violin's body, which converts this energy into the vibration of air which is sound. Nothing is amplified--no additional energy is added. A vibrating string produces nearly no sound because the narrow width of the string is too narrow to move much air. The violin body merely adds more surface area to efficiently move air. All the original harmonics of the vibrating strings are converted into harmonics of the sound produced. No new harmonics are produced. Some of the string's harmonic energy conversions are more efficient than others due to the violin body's various resonance peaks and valleys. This makes the sound output of a note's harmonics louder or softer. A note from a bowed note does have some non harmonic noise from various sticking and sliding of the bow hair on the string. If you play a single note and do an Audacity plot you will see some random noise between the harmonic series. For example if you play an A note with a frequency of 220hz, its next harmonic will be 440hz, and the next one 660 etc. In between these peaks there will be many much lower random noise peaks between the 220 and 440 peaks etc. But this noise is not created by the violin body--it is produced by the string/bow interaction. The violin body merely converts this random string vibration energy into sound noise energy.
  16. The wings vibrate widely at their resonance frequency but they are too small to produce sound. However due to a conservation of momentum if the wing is going up and down some thing else is going down and up at the same time. If this other place is big enough such as a node of the top plate at this frequency it will produce some sound. Placing a weight on the wing tip will lower its resonance frequency and some plate region will vibrate at this frequency and produce more sound at this lower frequency and the change can be heard.
  17. If the tuning fork pitch is the same as the frequency of one of the violin's resonance peaks the sound will be loud. If it is the same frequency as one of the valleys between the peaks the sound will be much much less loud. A bowed string has many harmonics which are integer multiples of the fundamental pitch f: 1f, 2f, 3f, 4f, 5f, 6f..... the amplitudes of each of these harmonics follows a decreasing sequence 1/1, 1/2, 1/3, 1/4, 1/5, 1/6.... This forms a "saw tooth wave" form. Each one of those harmonics can fall on a violin's bridge resonance peak, valley, or some where in between. So some of the harmonics might be high amplitude while others low and the resultant note will be a summation of all of these different amplitude harmonics. Thus the bridge's frequency response curve acts as a filter which changes the shape of the bowed string saw tooth wave. The violin's body acts as another subsequent filter with its frequency response curve changing the amplitudes of all of the note's harmonics which further changes the shape of the bowed string's saw tooth curve. This is shown in the attached diagram taken from one of Colin Gough's presentations https://acousticstoday.org/wp-content/uploads/2016/06/Gough.pdf Thus a filtered bowed note for example can sound "boomy" and loud if its fundamental frequency and its second harmonic happen to have a high amplitudes and conversely the note can sound "tinny" and weak if the first few harmonics have low amplitudes. Every note has a different series of harmonics and it is apparent that the sound character and loudness of each of these notes depend upon how their harmonics are filtered by the bridge and violin body. If you are a serious student of the support I suggest doing a Google search on "Colin Gough, violin" and read many of his free publications and watch his Youtube presentations.
  18. If you are making violas I suggest having a commercial table at the American Viola Society Festival if we ever get over this Covid mess. Many players and educators go to these. There are other similar viola organizations and events.
  19. Stradivari had about 90 unsold violins in his shop when he died. With many more years of hard work I think I can do that too.
  20. Rocks are heavy. Putting powdered rocks on a violin makes it heavier and less loud.
  21. The shape of a viola can be approximated by a circular disk which has a fundamental mode frequency f proportional to its thickness t divided the radius R squared: f ~t/R^2 This can be rearranged to show the the thickness t is proportional to the frequency f times radius R squared: t~f R^2 So if you want to keep the same mode frequency to keep the same sound character of the Quarneri viola the thickness of your 85% smaller viola should be reduced by about 0.85^2 or 0.72 or 72%. This assumes the wood has the same speed of sound which never happens.
  22. That's what I think too natural looks best. If you like dark colored wood, use a dark colored wood rather than using a light color one with stain or colored varnish. There's plenty of choices--cherry, walnut, chestnut etc. What kind of pie did that turn out to be? Along the same lines, I like straight apple pie with no added spices at all--no cinnamon, nutmeg etc. No sugar either. What
  23. I suggest the quality (sound, appearance?) has to be better than Chinese instruments at the same price.
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