Marty Kasprzyk

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Everything posted by Marty Kasprzyk

  1. Oops, I forgot the attachment I promised: Papers_BeyondtheSpectrum.pdf
  2. Thanks Anders. I got it! But I was disappointed that its references weren't as new or extensive as I had hoped. I've attached an older study which I think is excellent and it addresses the noise aspect of musical sounds very well. The violin's sound is often compared to human speech because it can be so changeable and expressive. Noise, both transient and steady state, is important as David mentioned. For example if you say the word "smooth" and do an fft analysis (see the attachment) of the starting transient sm portion sound it is all high frequency non harmonic noise with a hiss like sound coming from air passing over the speaker's lips. The steady state oo portion is has a low frequency fundamental with several harmonics coming from the vocal cords and resonances in the speaker's mouth and throat cavity. The ending transient th portion is again mostly noise from air passing over the speaker's lips again. Notice that the transient sm noise sound and the th noise are slightly different. This is because the person's tongue is placed differently. These high frequency starting and ending transients are very important in word recognition and expression so it is not at all surprising that they might be important too for violins. So I'm guessing that a 2000-4000Hz "bridge hill" of a good violin is helpful for producing ---noise! Many of the different bowing techniques players use affect these starting and ending transients which are used for conveying different feelings. I'm hoping to see if the violin's construction can help or hinder these bowing effects.
  3. Non harmonic noise seems to be important. For some reason I haven't been able to download the the below article which is fairly recent. It probably has a good list of references. ASA, Proceedings of Meetings on Acoustics, Volume 29, Issue 1 > 10.1121/2.0000376 Published Online: 08 February 2017 Accepted: December 2016 Relation between violin timbre and harmony overtone Proc. Mtgs. Acoust. 29, 035001 (2016); Masao Yokoyama1, Yoshiki Awahara1, and Genki Yagawa2 ABSTRACT The timbre of violins has been studied by several researchers from various points of view including structure, acoustic characteristic, chemical composition of the varnish and acoustic radiation. Although many of them have mentioned that Stradivari’s violin gives the most beautiful timbre, none of them clarified the reasons. In our previous study the timbreof about 30 violins from old ones to new ones had been studied and the relation between harmonic overtones and the expression words, which the audience receives from the sound of the violin, was analyzed. However, clarifying how the structure of overtone is related to the feeling of the listeners of sound such as “rich,” “bright,” and “soft.” was not successful. In this paper, the changes in overtone structure relating to violinist’s performance were analyzed. For instance, the power of non-harmonics frequency, which was assumed as noise,in “powerful” and “rich” expression was larger than that of the scale tone without expression.
  4. Hi Anders, Its good to hear from you again. I believe a program could be easily written to all do these plots nearly instantaneously but I haven't asked George if his new software version can do this. I play each note and do an Audacity fft analysis of it. I record the amplitudes of the harmonics of each note in a Microsoft Excel spread sheet and use Excel to do the 3d plot. This is very time consuming and I don't recommend doing it unless you're snowed in. An easier way is to just do a quick finger nail tap to the bridge and do an Audacity fft test. The amplitudes at each sampling interval can be seen as columns of numbers. You can just go down the list and pick the amplitudes for each harmonic. This data can also be put into an Excel spread sheet and plotted. When I do the bowing method I also write down my impressions of each note (weak, wolfy, harsh, tubby, bright etc.). This gives me an idea of what the shape of harmonic profile does and it's a good learning exercise. I believe a good instrument doesn't have a lot of problem notes. The 3d sea shore plot doesn't have big mountains, deep valleys or wide plains. The loudness each note is also taken from the same Audacity recordings and I make old fashioned Saunders Loudness type plots to compare my violins with Saunders' tests on Strads etc.
  5. I agree that frequency response graphs are difficult to interpret. I think a better way of presenting the data is to show the amplitudes of each note's harmonics. Attached is a plot of the first 25 harmonic amplitudes of the first 40 notes of one of my violas starting with the open C string shown in black in the upper right hand side of the graph. The open G, D, and A strings are also shown in black and the intermediate half notes have the same octave color sequence. Ted White calls this type of plot as "hills going down to a sea shore" to helpfully give a visualization of sound. Notice that the open C string note has many upper harmonics and, if you look carefully the fundamental (first harmonic) is indeed low. This note might be called "complex" or "rich". On the other hand the open string A note has a strong fundamental and only relatively few upper harmonics and this note might be described oppositely as "pure" or "bell like". It should be apparent that it is impossible to describe an instrument with just a few words. Unfortunately it is very tedious to generate these type of graphs and only a few bad, good, and great violin examples have been studied by others this way. I live on nearly flat land on the shore of Lake Ontario and it's peaceful and people come to watch the sunsets. But in other places people go to watch ocean waves crashing into the high cliffs of mountains.
  6. Unfortunately no because I attach my one piece neck/fingerboard/tailpiece assembly differently than on a conventional violin. I think we can all agree that the conventional violin has evolved to a state of perfection that can not be improved upon. So I gave up trying--there's no sense in beating a dead horse. My experimental violins and violas have good projection but they are often criticized because they sound too bright and harsh which is opposite of the warm and mellow sound I'd like to have. Frequency response curves show a lot of high frequency sound output from having too many high harmonics. My plates have no arch, little downward string force, and no longitudinal string force and my results are opposite of what I expected. Maybe my schools were no damned good.
  7. Mixing violin varnish with powdered sodium nitrate might make a good explosive or rocket fuel.
  8. I suspect the standard violin string angle is a result of practical compromises made with little regard to sound output or character. The bridge has to be high enough to give adequate bow clearance for the C bout's width with a bridge curvature that makes bowing of individual strings easy. A string angle across the bridge of 180 degrees would make a straight line across the bridge and there would be no downward force on the bridge from the strings. Sound would still be produced because it is a result of sideways vibration of the bowed string which causes the bridge to rock back and forth which in turn makes the plates vibrate. A downward string force is not needed to produce sound despite what some people believe. A strait or nearly straight string angle close to 180 degrees could be obtained by using a real short bridge but as implied above this would make individual string bowing impossible (some early history instruments had low bridges and only chords could be played). A better way is to use a higher neck overstand or higher saddle, or a combination of both. The only advantage of having a nearly straight string angle is that it reduces the static load stresses on the top plate. On the other hand a some string downward force from using a steeper angle keeps the strings in their notches during hard bowing. The downward string force also keeps the bridge in position.
  9. There's two discussions goin on. One about the strings and one on the violin body. Theoretical strings have a multiple of harmonics all with perfect octaves apart. But in real strings the very highest harmonics might not be exact multiples of the fundamental because the strings are not perfectly flexible like a chain. This small amount of stiffness causes a drift away from perfect multiples at the very high end. A violin e string, for example, has a solid steel core so it isn't very flexible. The lower strings have bundles of small diameter filaments in their core in order to make the string more flexible. Different brand strings with different construction might show different amounts of drift and therefore sound differently. The different brand strings also may have different damping which can reduce their high frequency output thus the string choice is important for controlling the high frequencies. On top of all that the string tension also plays a role. The violin structure (including the bridge) acts as a filter-transducer like Don mentioned which increases or decreases various frequency outputs. Because people have various likes and dislikes and hearing ability there is a large range of "good" sounding violins having different roll off frequencies. In general if the roll-off frequency is too low the violin will sound "tubby" because high frequency harmonics are absent. If the roll-off frequency is real high the violin may sound harsh to some people who have good high frequency hearing.
  10. One of Andreas' original questions was: "So what do overtones do to the sound?" If a note has too many high amplitude harmonics it may sound rough or harsh. Good violins (I assume Don's violin example is a good one) have a frequency response curve having a high frequency roll off at about 3000Hz. I've attached below a discussion regarding this. _art_1,_July_9,_2016.copy
  11. That's not the correct definition of "overtones". Nevertheless it is an interesting question: What is the importance of sound output over 3000Hz?
  12. The fineness of the microstructure might be a key factor in wear resistance and sharpness. Powder metallurgy sintering might give smaller grain size than older forging, casting, and heat treatment processes.
  13. I'm an engineer too so I just naturally drifted into viola making without thinking about it much. That's the nice thing about viola making--you don't have to think much.
  14. Hopefully you will overcome this handicap.
  15. I use similar forms. The holes around the perimeter are for positioning bolts used to clamp the top plate and ribs together instead of using the usual spool clamps. The same fixture is then used to then glue the back plate on. Its use ensures that the two plates remain flat and parallel along their edges without having any twist or cupping in the assembled body.
  16. You've been exposed to a contagious mental disease.
  17. Perfect, really perfect rows just like you see in North Korean or Chinese military parades. I used to play in a marching band where a precision of conformity was demanded. These perfect rows of planes aren't eye candy for me.
  18. In order to get the long bands of medullary rays the wood's surface has to be perfectly quartered. Maple wood has these rays too but they're not nearly as large or so darkly colored.
  19. Could somebody please play some lousy instruments. My violin teacher once told me "You don't know what happiness is until you've have experienced sadness."
  20. I found that a stiff bass bar reduces the amplitudes's of the lower frequency resonance peaks such as A0 while not affecting the high frequency resonance peaks much. So a stiff bass bar gives the perception of a brighter sound by decreasing the low frequency output rather than by increasing the high end as is often mentioned. Another impression is that it takes a big change in the bass bar height to have a noticeable sound character change.
  21. I use a glass plate with sandpaper starting with coarse grit and ending up with fine. With practice you can learn to use alternating hands to hold the bridge down on the sandpaper and trim all your fingernails.
  22. I forgot to mention that when you bolt the neck onto the body the fingerboard should be pointed upward.
  23. One of my violas was similar. I slotted the block for the bolt so the neck could slide up and down. The bolt screwed into a nut and I used a wide washer to prevent damage to the wood.
  24. A deep sounding C string is often cited as a beneficial characteristic of large violas. But I've found for my violas that the flexibility of the entire shell--top plate, back plate, and ribs is a major factor. A small viola with thin plates and ribs can have a deep sound. A small viola is easier to fit into an airplane's overhead compartment.