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Natural Science Forum / Physics / Acoustics / June 2004Guitar String: Stroke Speed & Dynamics
Recently there was a discussion on rec.music.classical.guitar concerning whether the speed of a finger stroke by itself has any influence on dynamics. During this discussion, I tried to find literature that directly answers this question. Surprisingly, I found nothing. Since I'm not a acoustical physicist, however, I'm doubtless overlooking sources obvious to those better versed in the field. Specifically, I'm looking for sources that directly answer this question: can stroke speed itself, independent of other factors (finger pressure on the string, direction of stroke, etc.), alter the dynamics of a plucked string? Also, are there any high speed film studies of a plucked string? Tom Poore Cleveland Heights, OH USA > Specifically, I'm looking for sources that directly answer this > question: can stroke speed itself, independent of other factors > (finger pressure on the string, direction of stroke, etc.), alter the > dynamics of a plucked string? Torsional agitation, btw. only really attainable by playing with the finger tips. > Also, are there any high speed film studies of a plucked string? > > Tom Poore > Cleveland Heights, OH > USA  Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* > Specifically, I'm looking for sources that directly answer this > question: can stroke speed itself, independent of other factors > (finger pressure on the string, direction of stroke, etc.), alter the > dynamics of a plucked string? A physics no-brainer. The faster it is stroked, the more impact sound generated as compared with the mere energy relase of a pluck. Imagine morphing between a harspichord (plucked) and a piano (struck). Then you have a model of the range of sounds or nuances you can create manually with a guitar. Angelo Campanella --------- www.CampanellaAcoustics.com --------- "I have simply studied carefully whatever I've undertaken, and tried to hold a reserve that would carry me through." - Charles A. Lindbergh. "As for background noise level; 35 dBA is a good classroom; 45 dBA is a sound masking system!" - Anthony K. Hoover > > Specifically, I'm looking for sources that directly answer this > > question: can stroke speed itself, independent of other factors > > (finger pressure on the string, direction of stroke, etc.), alter the > > dynamics of a plucked string? > A physics no-brainer. The faster it is stroked, the more impact sound > generated as compared with the mere energy relase of a pluck. > Imagine morphing between a harspichord (plucked) and a piano (struck). > Then you have a model of the range of sounds or nuances you can create > manually with a guitar. No. That concept fails to include torsional vibration. > Angelo Campanella Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* Here are some references that I know of that can shed some light to your inerrogation. One of the authors worked on a piano hammer-string interaction for his PHD. These are: 1. J. Bensa, S. Bilbao, R. Kronland-Martinet, and J. O. Smith III, ``The simulation of piano string vibration: from physical models to finite difference schemes and digital waveguides,'' Journal of the Acoustical Society of America, pp. 1095-1107, Aug. 2003. 2. A. Chaigne, ``Viscoelastic properties of nylon guitar strings,'' Catgut Acoustical Society Journal, vol. 1, pp. 21-27, May 1991, Series II. 3 A. Chaigne, ``On the use of finite differences for musical synthesis. application to plucked stringed instruments,'' Journal of the d'Acoustique, vol. 5, no. 2, pp. 181-211, 1992. 4. A. Chaigne and A. Askenfelt, ``Numerical simulations of piano strings. I. a physical model for a struck string using finite difference methods,'' Journal of the Acoustical Society of America, vol. 95, pp. 1112-1118, Feb 1994. 5. A. Chaigne and A. Askenfelt, ``Numerical simulations of piano strings. II. comparisons with measurements and systematic exploration of some hammer-string parameters,'' Journal of the Acoustical Society of America, vol. 95, pp. 1631-1640, March 1994. 6. A. Chaigne and A. Askenfelt, ``Numerical simulations of piano strings, parts I and II,'' Journal of the Acoustical Society of America, vol. 95, pp. 1112-1118, 1631-1640, Feb.-March 1994. Cheers. Erick OGAM. > > Specifically, I'm looking for sources that directly answer this > > question: can stroke speed itself, independent of other factors [quoted text clipped - 16 lines] > "As for background noise level; 35 dBA is a good classroom; 45 dBA is a > sound masking system!" - Anthony K. Hoover The full text in English of the PHD thesis I mentionned in my last post is at this link http://tel.ccsd.cnrs.fr/documents/archives0/00/00/35/68/ Bensa, Julien. Analysis and synthesis of piano sounds using physical and signal models. Thesis / PhD (23 May 2003), Laboratoire de Mecanique et d'Acoustique, UNIVERSITE DE LA MEDITERRANEE - AIX-MARSEILLE II. http://tel.ccsd.cnrs.fr/documents/archives0/00/00/35/68/ > Here are some references that I know of that can shed some light to your > inerrogation. One of the authors worked on a piano hammer-string interaction [quoted text clipped - 51 lines] > > "As for background noise level; 35 dBA is a good classroom; 45 dBA is a > > sound masking system!" - Anthony K. Hoover Assuming you're just playing a single string, I suspect the differrence is negligable. Are you strumming with your finger tip? your fingure nail? a pick? Stroke speed will affect how fast the string is displaced. It will also have a slight affect on how fast the string slides over the fingure nail. I believe the speed that the string slides over the fingure nail is primarly dependent on how far the string has been displaced and not stroke speed. > Recently there was a discussion on rec.music.classical.guitar > concerning whether the speed of a finger stroke by itself has any [quoted text clipped - 13 lines] > Cleveland Heights, OH > USA /* fixing top post ... yawn ... */ > > Recently there was a discussion on rec.music.classical.guitar > > concerning whether the speed of a finger stroke by itself has any > > influence on dynamics. During this discussion, I tried to find > > literature that directly answers this question. Surprisingly, I found > > nothing. Since I'm not a acoustical physicist, however, I'm doubtless > > overlooking sources obvious to those better versed in the field. Your first source is an instrument and listening. > > Specifically, I'm looking for sources that directly answer this > > question: can stroke speed itself, independent of other factors > > (finger pressure on the string, direction of stroke, etc.), alter the > > dynamics of a plucked string? Stoke speed appears to be directly correlated with the amount of energy transferred to the string. This because it is the hit on the string that supplies the energy that can be radiated as sound. >> Also, are there any high speed film studies of a plucked string? Probably. If not made by other people then made by those who write musical synthesis algorithms. > > Tom Poore > Assuming you're just playing a single string, I suspect the differrence is > negligable. I do not understand how this could be so. > Are you strumming with your finger tip? your fingure nail? a > pick? Energy in collision between implement and string is what is available to produce sound with. Energy increases with speed of implement in relation to string. > Stroke speed will affect how fast the string is displaced. It will also > have a slight affect on how fast the string slides over the fingure nail. I > believe the speed that the string slides over the fingure nail is primarly > dependent on how far the string has been displaced and not stroke speed. I recently had a guitar player ask what I was doing with my left hand while hitting a guitar string in different ways with my fingertip. I was doing nothing at all, other than holding the string in question to a fret, with a finger on my left hand. There is a very large variation in terms of how "hitting a string" sounds, imo to a large extent because of the varying amounts of torsional modes that are set up. Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* > Stoke speed appears to be directly correlated with the amount of energy > transferred to the string. This because it is the hit on the string that > supplies the energy that can be radiated as sound. The string's energy is, for the most part, dependent on how far it has been displaced prior to being released. > > Assuming you're just playing a single string, I suspect the differrence is > > negligable. > > I do not understand how this could be so. Stroke speed is relavent when one plays chords. This is because you are playing 3+ notes in stead of 1, and one will hear a differrence in the time intervals between each string's plucking. > Energy in collision between implement and string is what is available to > produce sound with. Energy increases with speed of implement in relation > to string. Its not very much energy. Most of the vibrations are damped by the pick/hand, and very little sound is produced. The stroke displaces the string, giving ride to tension, and thus potential energy. When the string is released the potential is converted into vibrational energy. > I was doing nothing at all, other than holding the string in question to > a fret, with a finger on my left hand. There is a very large variation > in terms of how "hitting a string" sounds, imo to a large extent because > of the varying amounts of torsional modes that are set up. I'm not familiar with the term "torsional modes". best wishes sgm >> Stoke speed appears to be directly correlated with the amount of energy >> transferred to the string. This because it is the hit on the string that >> supplies the energy that can be radiated as sound. > The string's energy is, for the most part, dependent on how far it has been > displaced prior to being released. And magnitude of displacement is likely to be proportional to stroke speed. > > Energy in collision between implement and string is what is available to > > produce sound with. Energy increases with speed of implement in relation > > to string. > Its not very much energy. Most of the vibrations are damped by the > pick/hand, and very little sound is produced. I don't think you read what I write, but rather that you read something else into it that isn't there. Energy in collision between implement (plectrum, finger, bow, whatever) and string is what is available to produce sound with. What other source of energy supplier for the string is it that you envision when claiming the suggested source irrelevant due to "not very much energy". > The stroke displaces the string, giving ride to tension, > and thus potential energy. When the string > is released the potential is converted into vibrational energy. Yes! - and displacement is a linear consequency of speed of stroke. >> I was doing nothing at all, other than holding the string in >> question to a fret, with a finger on my left hand. There is a >> very large variation in terms of how "hitting a string" sounds, >> imo to a large extent because of the varying amounts of >> torsional modes that are set up. > I'm not familiar with the term "torsional modes". Ah well, is "torsional vibration of the string" a better expression? - it appears that it was considered preferable to hit the string of a classical guitar with the fingertip prior to Segovia's reign because of the superior tonal quality, at least from quite old-style the guitar school booklets I have. Listen to Mark Knopfler, he must have read the same book .... fingertips, not nails, rule. > best wishes > sgm Fascinating topic, fascinating instrument, if only I had started way earlier ... Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* If one were to, say, hit a string and leave their hand on the string without ever releasing it, a small sound would be made. This is what I consider to be a collision. The sound would be much more noticeable in high gain situations. A faster stroke speed does not necessarily mean a larger displacement. There are many other contributing factors. The other energy I speak of is the potential. The potential results from the work that is done on the string during its displacement. >>Ah well, is "torsional vibration of the string" a better expression? hmmnmn....I've never had a course in acoustics. Would "harmonic oscillation" work? Regards, Steve M. --------------------------------------------- A Simple Method For Producing Digital Reverb Filters: http://2pi.us/rir.html An Algorithm For Guitar Distortion: http://2pi.us/dist.html > >> Stoke speed appears to be directly correlated with the amount of energy > >> transferred to the string. This because it is the hit on the string that [quoted text clipped - 50 lines] > > Peter Larsen > If one were to, say, hit a string and leave their hand on the string without > ever releasing it, a small sound would be made. This is what I consider to [quoted text clipped - 3 lines] > I speak of is the potential. The potential results from the work that is > done on the string during its displacement. Obviously, a slow pull and sudden release, or pluck, is the mathematically simplest situation to analyze, as it is a simple concept, and potential energy and wave shape are therein clearly defined. But that may not be musically 'interesting' (except for mathematicians, bless their soul). The wide variety of guitar string attacks, releases and strokes possible make for terribly complex mathematics, but makes the interesting musical sounds that we all enjoy so well. Since there are more musicians and listeners than there are mathematicians............ Ang. C. > If one were to, say, hit a string and leave their hand on the > string without ever releasing it, a small sound would be made. > This is what I consider to be a collision. It should be obvious from the context that so is not the way I used that expression. > The sound would be much more noticeable in high gain > situations. I'm just talking about a single guitar. Let us leave amplification well out of this. > A faster stroke speed does not necessarily mean a larger > displacement. I think we should agree to see this differently, lest we produce a lot of empty ascii of no interest to the group in question. > There are many other contributing factors. The other energy > I speak of is the potential. The potential results from the > work that is done on the string during its displacement. The potential energy stored in the string is simply proportional to the displacement amplitude. >> Ah well, is "torsional vibration of the string" a better >> expression? > hmmnmn....I've never had a course in acoustics. Would "harmonic > oscillation" work? No. I am talking about rotation of the string, that generally is what torsion implies. > Steve M. Kind regards Peter Larsen Signature******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
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