Guitar Physics

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Guitar Physics

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jmb

Posts: 119
Joined: Oct. 14 2014
From: Vallecas - Madrid - Spain

Guitar Physics

Perhaps, this has be treated but I did not find. I would like to know if there is any interesting physics paper or scientific review about the sound an the waves in a guitar that could explained the shape of the body, 'varetaje', resonances, etc. I read a paper with analysis about Guarneri ans Stradivari and it was really interesting for me.

Thanks in advance.

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Suenas payo ¡y lo sabes!

Sing and string - other flamenco blog

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 16 2014 14:48:24

krichards

Posts: 597
Joined: Jan. 14 2007
From: York, England

RE: Guitar Physics (in reply to jmb)

You could start with this

http://www.liutaiomottola.com/myth.htm

But be aware, you're opening a can of worms here. I was a physics teacher for more than thirty years and now I'm a luthier, and I can tell you that everything about the guitar is complicated.

Don't believe anyone who has an easy answer.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 16 2014 15:33:49

keith

Posts: 1108
Joined: Sep. 29 2009
From: Back in Boston

RE: Guitar Physics (in reply to jmb)

al carruth has done a lot of research and is well respected. here is a link

http://www.alcarruthluthier.com/Acoustics.htm

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 16 2014 16:41:06

Ricardo

Posts: 14825
Joined: Dec. 14 2004
From: Washington DC

RE: Guitar Physics (in reply to jmb)

J. Ramirez III says in his book he did a lot of his own investigation into Physics of sound in 3D Space in order to settle on his De Camera model guitar... but doesn't give any specifics interms of equatitions or experiments. What he arrived at was the guitar with an inner "fin" with a large hole in the shape of the guitar body. Never played one but he seemed quite proud of it in his book.

Ricardo

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 16 2014 17:49:35

estebanana

Posts: 9354
Joined: Oct. 16 2009

RE: Guitar Physics (in reply to jmb)

There's a saying:

"Luthiery is not rocket science, it's harder."

________________

Read Alan Carruth's works, he is vetted and does not do dumb experiments. His work is carefully done and checked, and he works on problems that have practical applications in real building. His stuff is pretty solid and some of it is quite difficult to read unless you have some advanced science background.

In particular his study of saddle break angle is excellent and his big work called 'String Theory' is very good. Despite the obvious pun in the title, it is an exhaustive look at guitar strings in tension, motion, structure and what happens to them as they move. He figures out some things we already knew by ear, and few new things we did not know.

Some people also swear by the book of the Australian called Trevor Gore, but he kind of uses the research to support a proprietary bracing system and the cost is prohibitive for casual reading. But he did a lot of work.

One thing to remember is that many things on the guitar seem provable with physics, yet in practice the guitar does not actually function as is is proved out to function. Like if you think the treble side of the bridge and treble side fan braces control the treble strings you would be scientifically wrong. Yet there is some bearing to the common sense visual logic as it applies to guitar function. It is truly a strange and contradictory box.

And the tone generation science where makers excite the guitar with a tone to see how the various points resonate. That stuff does work to a degree, but good guitars also don't adhere to the same parameters that other good guitars show. There are different kinds of 'good' guitars. Carruth says, we know how to make a good guitar almost every time after looking at the research, but we are still figuring out how to make a great guitar.

The great guitar is probably not possible to quantify, good guitars fall into some what calculable ranges.

After nearly 500 years, violinmakers are still not clear on why the bass bar functions. They know if you whittle it here or there it changes the violin a bit, but not really why.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2014 1:56:37

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Guitar Physics (in reply to jmb)

quote:

After nearly 500 years, violinmakers are still not clear on why the bass bar functions. They know if you whittle it here or there it changes the violin a bit, but not really why.

And that explains lutherie very well. We work A LOT with intuition and impirical experience.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2014 8:39:48

jmb

Posts: 119
Joined: Oct. 14 2014
From: Vallecas - Madrid - Spain

RE: Guitar Physics (in reply to jmb)

Thanks, I think it is a very interesting field. I have skimed what is in Internet, but mos of the studies are related with chladni patterns and other vibrational issues. Bracing and wood type seem to be very important. But no too much about other microscale issues.

For example. One paper that capture my attention was some clinical(sic) images o a violin (I can't not find it now, sorry) There was a tomography (a CAT scan) image of a violin and it was curious that the the axial image of the grain, in of the bulk of the top, was crosswise. I mean that the image of its section was something like "////" and not something like "|||||" as I expected. And despite de distance bettween lines in surface was regular the inclination was high considering the few milimeters. I have read that the grain (lines) of the top is a kind of strings that vibrates at the same time and get amplification (perhaps I wrong) and I wondered if that inclination could induce changes in the sound. The image was quite impressive for me because of the high grade of perfection in the surface and simetry of the wood that you get in the guitars and then this so thin and hide wood bulk showing so irregular. But like in biology, the tricky is that you work with live beings

: the trees.

Thank you very much for you contributions. I will continue learning about your really interesting alquemist's work.

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Suenas payo ¡y lo sabes!

Sing and string - other flamenco blog

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2014 14:54:05

Richard Jernigan

Posts: 3431
Joined: Jan. 20 2004
From: Austin, Texas USA

RE: Guitar Physics (in reply to Ricardo)

I read Ramirez's book after I had spoken to him a number of times in the process of buying over a period of a few years about a dozen 1a classicals, which I imported to the USA. As a practicing physicist and engineer, I could not see where his ideas had a scientific foundation. All the same, he produced fine guitars, and I still love my '67 1a blanca.

Carruth, on the other hand, strikes me as a very well informed 'scientific' luthier, who has performed a number of ingenious experiments that shed light on topics not readily accessible to calculation. Any engineer or physicist will know that a calculation is not to be trusted unless verified by experiment. Carruth sums up by saying, "Through measurements we can tell a good guitar from a bad guitar, but we can't tell a good guitar from a great guitar."

RNJ

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2014 15:21:32

Richard Jernigan

Posts: 3431
Joined: Jan. 20 2004
From: Austin, Texas USA

RE: Guitar Physics (in reply to jmb)

Grain pattern in guitar tops: One of the most famous classical guitars of the 20th century is Julian Bream's 1973 Jose Romanillos. I have seen it up close. The grain lines are spaced quite widely in the center, for a guitar top. The spacing narrows toward the outer edges, then widens again. I own the guitar made just before this one. The top looks like it could be the next board in the flitch to Bream's. In an article by Kevin Aram in the Journal of American luthiery, Romanillos is quoted saying guitar tops were hard to come by in England at the time. He resorted to re-sawing 'cello tops.

The well known Mexican luthier Abel Garcia Lopez studied with Romanillos, and twice served as his assistant at his guitar making course at Guijosa in Spain. When I visited Garcia to order a guitar from him he showed me some tops Romanillos had given him from early in Romanillos's career. They were obviously from the same flitch of the tree as Bream's guitar and mine.

When I ordered from Garcia he offered a selection of backs and sides to choose from. I chose, but I said, "Maestro, you are the expert, you pick the top." He chose a piece of perfectly quarter sawn spruce with very fine straight grain. He said the wood from Romanillos would have been as good, but it might have made my guitar a little harder to sell if I wished to.

(I don't want to sell it.)

RNJ

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2014 15:39:41

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: Guitar Physics (in reply to jmb)

I'll swear by Trevor Gore's work
http://www.goreguitars.com.au/main/page_home.html
It's like Kevin Richards said
"Don't believe anyone who has an easy answer"
Trevor's books require quite a lot of effort to digest
Most of Trevor's techniques use little more than a computer, free software, scales, a microphone and a rubber eraser on a stick.
Plus a dial gauge and supporting jig if you want to measure soundboard flexibility.
I have spent 3 days with Trevor in a course and he is the real deal.
His guitars are outstanding, I have only played his steel strings and classical's, not his flamenco's which he uses a more traditional bracing on.

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 18 2014 4:31:49

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: Guitar Physics (in reply to jmb)

A problem that we, the luthiers, often face is when tecnically and theoretically minded non-luthiers try to cut the production of a stringed instrument down to small meassurable things and after doing that start asking us, the builders, a lot of questions based on these theories which they mean are important. Some even try to convince us that they, the non-builders, know more than those of us who build and when we dont take them serious, they get angry.
There´s a spanish saying: "Nothing is real until it has been transformed into experience"
The whole Spanish idea about building guitars is based on that. They dont put to much theory into their building. They do it step by step.

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REPORT THIS POST AS INAPPROPRIATE | Date Dec. 18 2014 8:46:39

jmb

Posts: 119
Joined: Oct. 14 2014
From: Vallecas - Madrid - Spain

RE: Guitar Physics (in reply to Anders Eliasson)

Yeah! I work in the world of life sciences research and, I understand what you say. In this world of electronics and road bridges most of the people think that all can behave as digital devices. It is very difficult to made people understand that one think is the equation(usually from a simplified model) [8| ]and other to control the equation in some works and fields.

Lots equations as the basic frecuency=speed/wave lenght in your case, involve wicked behaviours inside a guitar body. That was because I asked for papers about a deeper research that vibrometers.

Your work is titanic. Thanks you all.

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Suenas payo ¡y lo sabes!

Sing and string - other flamenco blog

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 18 2014 10:48:44