Acoustic Guitar Terminology"DAMPING"=Luthiers Please chime in

[AcousticDreams]

I have searched the internet for Acoustic Guitar terminology & can not seem to find a complete glossary of luthier terms..

I am very interested in descriptive scientific terms, that pertain to wood's sound.

*In particular, I would love to totally understand the complete meaning of "DAMPING", In its relation to wood's damping characteristics & how it effects guitar tone. So much is discussed about damping, and I do have a general understanding. But sometimes what we interpret, is not always the exact meaning as it was meant to be used. Descriptions and the context in which they are used, is sometimes hard to grasp.

So my purpose of this post is two fold:

1. Help me to understand what damping is, and how "Damping" wood properties effects sound ?

2. In particular I am extremely interested in Fingerboard materials. Ebony is known for its damping effect. Rosewood is known to not damp as well in comparison. However, there are those Heavier & harder Rosewoods such as African Blackwood, Brazilian Kingwood, That may exhibit similar damping characteristics to Ebony, due to their hardness and weight? OR not? That is what I would like to understand.
There are, as an example, custom Electric guitar makers who prefer using Rosewoods over Ebonies for fingerboard material. As where with acoustic instruments ebony has long been a favorite. Of course there are many acoustic guitars made with Rosewood finger boards as well.
The question is are there Rosewoods like AF & BK, that might exhibit some of the Characteristic of Ebonies, due to their Damping abilities? Obviously there will still be a difference in sound between them.

[rick-slo]

I would not sweat it on the fingerboard choice other than perhaps a cosmetic preference. Tonal differences are minimal. Personally I prefer ebony for looks and excellent wear resistance.

[charles Tauber]

Originally Posted by Knives&Guitars

In particular, I would love to totally understand the complete meaning of "DAMPING", In its relation to wood's damping characteristics & how it effects guitar tone.

The response of any translational oscillating mechanical system - the guitar is an example of such a system - is characterized by mass, spring stiffness and damping.

Damping is an influence within or upon an oscillatory system that has the effect of reducing, restricting or preventing its oscillations. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation.[1] Examples include viscous drag in mechanical systems, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators.

https://en.wikipedia.org/wiki/Damping_ratio

If you pluck a guitar string while holding your palm against the guitar top, you are mechanically reducing or restricting the amplitude of the oscillation of the guitar top. You are adding/increasing mechanical damping.

The wood from which a guitar top is made has inherent mass, stiffness and damping: they define, in part, the physical properties of the piece of wood. The amount of mass can be altered by the size, shape and thickness of the top, as well as by removing portions, such as is done with a sound hole.

Second, each piece of wood has, as part of its mechanical properties, a certain amount of inherent stiffness - resistance to bending and an accompanying tendency to return to its un-bent state. Many guitar makers choose pieces of wood that are inherently stiffer. Stiffness is also manipulated through thickness of the wooden component - resistance to bending is proportional to the cube of the thickness: stiffness is heavily dependent upon thickness. (So, there is the inherent stiffness of the material and how the stiffness of the component is manipulated through the geometric shape of the material.)

A third mechanical property of the material is its damping. Some materials impede oscillation - have higher damping - more than others.

The three of these, together, determine the response of the system. The acoustic guitar maker's task is to find the balance of these three elements that produces the sound (response) he or she wants, while having the instrument strong enough to withstand the string forces imposed on the instrument.

A guitar is a very, very complex mechanical system. There are many inter-related things going on, making it difficult to isolate any one of them and decisively conclude what result changes to that one variable has on the response of the entire system.

So my purpose of this post is two fold:

1. Help me to understand what damping is, and how "Damping" wood properties effects sound ?

The example of striking a string while holding your palm on the guitar top is an example of increased damping. Damping, whether due to the mechanical properties of the material, or due to an external mechanical application, can reduce vibrating amplitude and can increase the rate of decay of the vibration. One will tend to reduce "volume", the other duration of sound.

A good example of damping ratios can be found in automobile suspension systems. Japanese - and some European - cars are "over damped". When you go over a bump, the suspension responds with a single heavy thump and very little subsequent oscillation - it's a "hard" ride. Many North American cars are "under damped". When you go over a bump, the car floats up and down repeatedly, gradually reducing in amplitude. It is a much "softer" ride. That illustrates the response of varying amounts of damping. Guitars, of course, want "sustain", a result of being underdamped. In some guitars, a note is plucked and the sound immediately decays - too much damping.

2. In particular I am extremely interested in Fingerboard materials. Ebony is known for its damping effect.

While it is easy to state, "Everything has an influence on the sound", the unanswered question is just how much influence does each component have? Some believe that the material, and its properties, from which a fingerboard is made has an audible influence on sound. That might be true, but there isn't a lot of hard/scientific data to support that.

My suggestion is that the material properties of the fingerboard is way, way down the list of important contributors to the audible response of an acoustic instrument.

[AcousticDreams]

A very thorough response, Thank you Charles!

I have been told by some lutheirs, that ebony becomes a Neutral zone of sorts. Ebony does such a good job at Damping, that a fingerboard made from it, will effect the guitars tone less in comparison to other materials?

In this regard then, it is not damping the guitar itself...but rather letting the the rest of the Instruments parts influence the sound. That is how I have interpreted it. But I may have misunderstood, and wish to clarify an make sure I am understanding?

If this has any basis, am I am not saying that it does, as I honestly do not know, then my questions is directly aimed at African Blackwood and Brazilian Kingwood. They are seemingly heavier & with higher specific gravities, than our standard used Ebonies. Yet as we all know, AF and BK do not sound the same as Ebony. Of course if I am not understanding this correctly, then Damping for fingerboards would have an entirely different influence.

What scientific notation determines the Amount of Damping a wood species has? Is it Janka hardness? Crushing strength? Specific Gravity? Weight? or is there some combination there of? I have briefly read the great info and links provided by Charles, but I am not sure how to apply the Known data of AB & BK to determine their exact damping factors in relation to Ebonies.

[rick-slo]

Damping would be the fretboard wood absorbing the string vibrations (turning them into frictional heat) rather than transmitting them on
towards the body of the guitar. I suppose that might be a plus if you want a certain amount of decay to the sound. You might further color
the sound by frequency dependent variable absorption of the sound (such as happens with different top woods). I just think it does not
amount to much audibly in regards to the fretboard wood.

[mercy]

The way I look at it, on a neck is you want stiffness that restricts the ability of the neck/fingerboard unit vibrate and thus not eat energy. You want that energy to stay in the body to generate as much sound as it can. Ebony is very stiff so it is good for a neck and that makes it good at making a guitar more efficient. There are other ways to stiffen a neck of course.
I do not think damping is a factor for a fingerboard where it is very much a factor for a bridge. Ebony has higher damping than ei rosewood which has higher damping than any of the other rosewoods. You want your bridge not to absorb energy except with big guitars which help to balance them out.
So rosewood for smaller guitars and ebony for bigger guitars. Another factor is not the efficiency of the system but what youre used to hearing. You may like the sound of a "muffled" guitar. Change an ebony bridge for a rosewood one and it will sound different but you may not be used to that sound and so my not like it, or you may.

[AcousticDreams]

Originally Posted by mercy

The way I look at it, on a neck is you want stiffness that restricts the ability of the neck/fingerboard unit vibrate and thus not eat energy. You want that energy to stay in the body to generate as much sound as it can. Ebony is very stiff so it is good for a neck and that makes it good at making a guitar more efficient.

I really like this explanation Mercy, makes me look at this equation from an entirely new perspective. Thank you very much. That makes some good sense..

O.K...Where is Alan? Nobody is better at explaining scientific terminology than him!

[varve]

The best source for damping, specifically as it relates to lutherie is, IMHO, found in the excellent two volume set by Aussie luthiers Trevor Gore and Gerard Gilet, "Contemporary Acoustic Guitar Design and Build":

https://www.stewmac.com/How-To/Books...d_Edition.html

I just spent a very in-depth weekend at a modal tuning workshop run by Trevor Gore, and hosted by Robbie O'brien, in Colorado. We learned a great deal about all aspects of guitar acoustics, including damping.

In short, damping (or internal friction) results when guitar wood is compelled to vibrate. Some of the energy is lost to friction, instead of being radiated as sound, our desired outcome.

Low damping, therefore, will result in a long "ring" on the tap tone of the board. In the finished guitar, it could have a positive effect on the amplitude, and therefore volume, of a given note. It will NOT, by itself, have an effect on the modal frequencies at which a guitar vibrates efficiently. The position of these modal frequencies is an important, complex, but ultimately predictable intersection of design, Young's Modulus of the topwood, and density of said topwood and bracing.

In Trevor's words, then: "Low damping wood will, by itself, not guarantee guitar quality - a lot of other things have to be right. Once those things ARE right, however, then low damping can make the difference between a good guitar and a great one!"

The three day workshop, and volume one of the book set, is an incredibly thorough treatment of how exactly to "get those things right" . Both the yearly workshop, and the two volume set, is highly recommended.

Cheers,
Dave Olson

[AcousticDreams]

Starting to understand the importance of Damping in relation to the Balance of sound in a guitar.

In a good article I just found online they state many interesting factors. Trying to sum it up it states:

That there are peaks and valleys of the frequency response in stringed instruments(we have all seen those dynamic volume graphs when we visit some of the music cloud sites). These peaks and valleys make the instrument sound natural. In comparison, Some synthesizers have a more level output giving a different feeling altogether.
“In mechanical vibrating systems, the height of a resonant peak and the width of the peak are related to damping. The more damping present, the lower and wider the peak. The less damping, the higher and thinner the peak will be. To understand why damping is important to the tone of an instrument it is necessary to understand that a resonant peak can be driven by frequencies other than the center frequency of the peak. “
“But too much damping can be a problem. Not only does damping increase the width of a resonant peak, it also decreases the height of the peak. The lower the height of the peak the less sound it radiates. At some level a peak would be so low that it would not contribute much to the sound at all.
On the other hand, too little damping can be a problem as well. We've already discussed that the peakiness of the response of a stringed instrument is generally a good thing, because it makes for a more natural-sounding tone from the instrument. But what if the response were to be made even more peaky, reducing the width and increasing the height of the peaks?"

Some great information revealed here today by Charles Tauber, Rick-slo, Mercy, & Varve.

However I would still like to know how to figure out the damping factors of a particular wood species.
I would still like to know how African Blackwood and Brazilian Kingwood damp, in comparison to Ebonies? Obviously a wood being harder, weighing more, and more stiffness does not always mean that it necessarily has more dampening qualities? Or does it. What causes one wood to Dampen more than another?

[charles Tauber]

Originally Posted by mercy

The way I look at it, on a neck is you want stiffness that restricts the ability of the neck/fingerboard unit vibrate and thus not eat energy. You want that energy to stay in the body to generate as much sound as it can.

That's true in theory, but, possibly, not so much in practice.

In the 1960's Dr. Michael Kasha, a science professor at Florida State University, stated that the classical guitar is designed all wrong. He created a theoretical model of how the guitar, he thought, worked and worked with luthier Richard Schneider to implement those theories. One of those theories is that vibration/energy is "wasted" on the neck. To reduce vibration and energy transfer to the neck, they introduced a "rigid" H-shaped metal connection between the neck and body. They also added weight to the head of the instrument to increase its inertia, thereby increasing its resistance to vibration. He applied the concept of "impedance matching" to guitar theory.

To make a very long story short, the Kasha design, and its theories, never really caught-on with most makers or players. The theory sounded nice, but didn't really produce instruments that most players wanted to hear.

Another guitar maker of that era, Arthur Overholtzer, had his own ideas. One of his ideas was the use of rosewood necks for classical guitars. He was not in any sense a theorist, he simply felt that a heavy neck was desirable.

My own experience, regarding necks, has been the exact opposite: generally, the lighter the neck, the more responsive the instrument. Generally, the lighter everything, the more responsive the instrument.

I think the short answer is that there are many ways to make a "good sounding" guitar. There are many combinations of the main variables that produce satisfactory results. Sometimes one successful combination appears to be contradicted by a different successful combination. That leads many to confusion. As a simple example, take a braced guitar top. One maker might make a very thin top with tall bracing and get the "good" sound that he or she wants. Another maker might use a relatively thick top, but shorter bracing to get the "good" sound that he or she wants. Each has found a balance between mass and stiffness that give the desired response of the instrument. Both can work: they have used different values for the variables to end up with a "similar" result.

Ebony is very stiff so it is good for a neck and that makes it good at making a guitar more efficient.

An ebony fingerboard is not very stiff. It has 20 or so slots cut across its width that significantly reduce its stiffness. Compression fretting takes advantage of that lack of stiffness to bend the fingerboard and neck.

In terms of the response of a mechanical system, mass matters. Ebony is a very heavy wood, though stiff. It has a much lower stiffness to weight ratio than spruce, for example. For responsiveness, one usually desires low mass. One example of that are "double tops", where "veneers" of top wood sandwich a low-mass, mostly air, honeycomb centre. The result is a very light - low mass - top that is very stiff. If the top is made too stiff, say by using too much or too stiff bracing, bass response is sacrificed.

[charles Tauber]

Originally Posted by Knives&Guitars

However I would still like to know how to figure out the damping factors of a particular wood species.

Values are derived from physical testing. In the recent discussion on hot hide glue, a link was given to Tim McKnight's article on how he tested the damping quality of different glues. One could perform similar tests using identically sized pieces of different wood species.

This research, for example, https://www.sciencedirect.com/scienc...11379717302632, describes the testing methodology, one similar to Mr. McKnight's, and gives values of damping ratio for Indian rosewood, ziricote, African Blackwood and ebony, values of 9.6, 7.6, 8.1 and 9.8, respectively.

Now that you have those values, what will you do with them? What do they mean for the practical world of guitar making - or playing?

Guitar fingerboards have been made from a variety of woods. Good sounding instruments have been made with ebony fingerboards, with Indian rosewood fingerboards, Brazilian rosewood fingerboards, ziricote fingerboards, and so on. The determining factor of how responsive a guitar is, or is not, does not seem to have any direct correlation to the species of wood used for its fingerboard. There is no concrete evidence one way or the other: there is only subjective opinion.

[AcousticDreams]

Originally Posted by charles Tauber

Now that you have those values, what will you do with them? What do they mean for the practical world of guitar making - or playing?

Hmmm? Honestly I have no idea at this point how I will use this information as of yet. I am at least a year away from ordering another guitar. And more likely two years.( As high quality microphones are next on my list. I have been studying them now for several years).
I will need to study wood damping & its effects further.

But I do find this information totally fascinating. In that the hardest, densest material, African Blackwood does not have the greatest damping factor in comparison to Rosewood & Ebony. That is such interesting news. This explains part of the reasons why These two woods are the most frequently used materials for fingerboards. It also gives an explanation as to why African Blackwood would have a different tonal quality than ebony. While it is harder, denser, it has a lower damping characteristic.

And I like you added opinion about weight being a bigger factor with necks. Would love to have you expound more on this.

As you pointed out, In Reality, it would pretty hard to provide concrete evidence one way or the other. No debate there. There are so many variables in making an acoustic guitar it would be very hard for conclusive evidence. It is not something as easy as a saddles ( or bridge pins, ha ha...just had to through that in for giggles=please forgive me) that can be dropped in and out for comparison.

Regardless, it is fun to dream of how one component might effect the sound. Valid or not, it is always fun to theorize. Daytime theorizing is a staple for this old guy. Makes me feel young again.
*I have said this many times before, I might like experimenting more than actually playing. Creating, Building or modifying something with my own hands, discovering something new, is most gratifying.

[rick-slo]

Originally Posted by Knives&Guitars

But I do find this information totally fascinating. In that the hardest, densest material, African Blackwood does not have the greatest damping factor in comparison to Rosewood & Ebony. That is such interesting news. This explains part of the reasons why These two woods are the most frequently used materials for fingerboards. It also gives an explanation

Well this is in the neck fretboard situation. For the back of the guitar the density (weight) does have a noticeable effect. A dense, stiff wood such as
Macassar Ebony tends to suppress the power of the bass response as it vibrates less readily. Sustain is good.

[mercy]

African Blackwood and Gaboon ebony have about the same stiffness and hardness but AB is quite a bit heavier. That means to me that ebony is a better choice for a fingerboard as it has similar characteristics to AB but has less weight.
What is the most important factor in a fingerboard is its hardness because fingernails eat away at it. Since both woods have about the same hardness that gives ebony the advantage over AB as well as any of the other rosewoods. One person might like the look of rosewood better but ebony is the winner.
As far as sound that varies with the individual preference. For an example I dont like the Martin sound, I find it bass heavy, but I think most people do like it.
If we are talking efficiency thats different then we can talk numbers. Still I dont think the fingerboard makes much difference in an acoustic guitar sound. It has to some because it makes a great deal of difference in an electric guitar, solid or chambered.

[runamuck]

This is anecdotal, but my experience with various woods and their damping characteristics, have to do with high resin and mineral content such as silica. Take teak or lignum vitae as two examples, 2 woods that are terribly dead acoustically.