Spectrum Analysis For Bows


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There's obviously a lot of fascinating work being done on how to understand the tonal response of a violin through spectrum analysis. Given that different bows give very different tonal results on the same violin, is anyone looking at this?

If so, what's the methodology? I can understand how you'd make a violin vibrate (by hitting it), but how would you draw out the tonal characteristics of a bow?

Martin Swan Violins

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I believe Joseph Regh has.

He's also made an attachment which can create vibrations at different frequencies in the bow while playing, for experimental and demonstration purposes. It was interesting to experience how it can alter the way the bow behaves, like how well it seems to grip the string.

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That's very interesting, but has anyone discovered a means of control for bow spectra?

Of course - use different wood, camber, thickness distribution, head-height etc.

Incidentally, I was disappointed with the Bow chapter in the Rossing book. I was hoping that it would deal with some of this, but instead it dwells mainly with the hair/string slip-stick features of different bowings.

Jerry Pasewicz has a set of lectures by J.F. Marshall that deal with some aspects of the physics of the bow, but at a somewhat superficial level.

---------

Clunk...as the dropped name hits the floor.

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I suppose my question is whether the inherent tonal emphasis in any given bow can be measured, rather than just dimly perceived by a player.

From my point of view there are 3 or 4 different issues which influence my opinion of a bow - the inherent tonal quality is a big one, although the distinctions aren't as subtle as with violins. Do bowmakers aspire to an ideal of tone ... and if so, can spectrum analysis help?

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Of course - use different wood, camber, thickness distribution, head-height etc.

Yes, but what controls mentioned directly correlate to highly-specific adjustments in spectra and how do they correlate? Just saying that you can change those things doesn't tell us directly how they will impact the spectrum analysis.

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I suppose my question is whether the inherent tonal emphasis in any given bow can be measured, rather than just dimly perceived by a player.

From my point of view there are 3 or 4 different issues which influence my opinion of a bow - the inherent tonal quality is a big one, although the distinctions aren't as subtle as with violins. Do bowmakers aspire to an ideal of tone ... and if so, can spectrum analysis help?

Martin, my take is that they shouldn't. Not in the maybe narrower sense of violin tone. I think the bow is somehow more "personal", it has to fit the arm and bowing style of the player. Players like quite different bows. I'm not even an amateur player but like a soft bow. My wife plays all day long and despite being rather small likes a heavy, springy bow. I'd guess that bows are very personal.

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I haven't read it yet rolleyes.gif (downloaded in January)

Mechanics and acoustics of violin bowing

PhD by Erwin Shoonderwaldt.

In the second study the influence of the main bowing parameters on aspects of sound quality was analyzed in detail. It was found that bow force was totally dominating the control of the spectral centroid, which is related to the perceived brightness of the tone. Pitch flattening could be clearly observed when approaching the upper bow-force limit, confirming its role as a practical limit in performance.

Also

Acoustic Radiation from Bowed Violins for some methodology, and

http://www.phys.unsw.edu.au/jw/violintro.html#bowing

BOWED STRING PHYSICAL MODEL VALIDATION THROUGH USE OF A BOW ...

Probably not exactly what you want, but it's a start.

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Yes, but what controls mentioned directly correlate to highly-specific adjustments in spectra and how do they correlate? Just saying that you can change those things doesn't tell us directly how they will impact the spectrum analysis.

From personal experience I have noted several things about bows, some well described, others less so, and as a result I am also interested in trying to understand the basis of these observations.

Here are a couple:

- I can kill the tone of a violin by changing bows (well known to those who swap snakewood and pernambuco sticks, for example)

- I have the 'impression' that the best tone of a violin is be obtained by a bow that vibrates in the right hand with the largest amplitude (less well aired).

I have asked about these and other questions here and elsewhere, but so far I have only had partial explanations (of course, some of my observations could be stupid).

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This is why I think that tapping a violin can only provide a very partial answer to tonal quality.

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The type of rosin used plays a role in the produced tone.

This is something that I know all too well, and when many students ask me to help them find a new bow, I tell them to switch rosins first to something of higher quality whose consistency suits their playing style.

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The rosin and the hair are factors of course, but I handle dozens of good bows and always use the same hair and the same rosin. They have very different characteristics of weight, balance, spring and "grip", as well as varying degrees of granularity and differences in volume (not in any way connected to weight). But they also have tonal attributes which are not connected to any of these factors. That's what I'd like to understand. The player is the same (me!) ...

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The rosin and the hair are factors of course, but I handle dozens of good bows and always use the same hair and the same rosin. They have very different characteristics of weight, balance, spring and "grip", as well as varying degrees of granularity and differences in volume (not in any way connected to weight). But they also have tonal attributes which are not connected to any of these factors. That's what I'd like to understand. The player is the same (me!) ...

Yes, but for amateurs and students simply wanting a better sound, it's better to check these factors first before recommending they buy an entirely new bow. You replace the squeaky wheel, not the whole cart.

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Addie,

Thanks very much for these sources - looks very interesting. I will take a few days off and try to understand them!

I'd just like to re-state my question because we seem to have drifted slightly on to rosin - which is a sticky subject.

In the case of violin making, there's a broad consensus (for whatever reason) that early Cremonese instruments have ideal tone, and everyone is trying to emulate that, nowadays using spectrum analysis etc to aid in that process. Given that bows have strong tonal characteristics, are bow-makers similarly obsessed with the ideal tonal attributes of Peccates (for instance), and trying to emulate that by means of spectrum analysis?

Maybe there just aren't many bow-makers on this site ....?

Martin Swan VIolins

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The "tone" of bows doesn't seem to have attracted the same level of interest. Perhaps it's partly sociological. Stradivari(us) is almost a household word, and I have read countless general media articles mentioning the superior sound of Stradivari violins. I don't recall having ever read one mentioning the superior sound associated with a certain subset of bows.

Even in the music world, I've read many music critic reviews mentioning the sound of a violin, but no mention of the sound of the bow. Maybe bows need a good publicity agent. :D

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Would you say this to Mr Perlman when you ask him to play the Soil with a 70g snakewood bow?

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Shouts

OK - 65g bow.

I will probably not ask Mr Pearlman about anything, ever, I guess. I must admit that I do not know much about bows, my own are rather cheapy.

Guettler and Askenfeldt have done listening tests of bows with musicians and non musicians and the mus were able to detect which sound samples were played on the good bow. But the non mus were not able to, even if one of the sticks was a birch tree stick. The results were published in the CAS I believe, or maybe it was at a conference.

They were however not able to find anything in the spactra that could reveal the good from the birch stick..

I do have long time average spectra of scales using different bows on the same fiddle, my better bow gave more oomph in the lows. The test was a cheap carbon fibre bow against my phernambucco jumping "noname".

I'll might find the abstract of Guettlers article when I come home form my job. (- I'll deliver my taxwork first..)

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They were however not able to find anything in the spactra that could reveal the good from the birch stick..

As though birch bows have no redeeming qualities? biggrin.gif They make cheap uneven instruments sound uniformly boring, which is, no doubt, part of the reason they were shipped with Saxon/Bohemian VSO's.

I wonder if the lack of research has anything to do with the fact that a Strad will sell for millions but a Tourte only thousands?

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Wise words!

Which comes first, the price tag or the acknowledgement of superior tonal attributes?

Peccates are now fetching £35,000 plus ... I don't think spectrum analysis will follow far behind!

The highest dollar amount I found on Christies for a bow was $74K, pretty close to your £35K.

I wonder what the tonal influences are of the "hatchet head?"

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