Measuring Good Vibrations

Chris writes "A laser vibrometer finds its first application analyzing the vibrations in a guitar when different strings are plucked. The laser Doppler vibrometer (LDV) measures displacement and vibration speeds at 16 separate points simultaneously. The first application of the XVI is musical, analyzing the vibrations produced in a guitar when its E-string (the fattest string) was plucked. Analysis of this kind could prove useful for enthusiasts and manufacturers trying to replicate the sound made by old musical instruments in their new designs. They want to know what made these old instruments sound so good."

Comments

oh great

[nocomment]

Now we're gonna have "Live Double Doppler" on guitars too?

Why so good?

[gnovos]

They want to know what made these old instruments sound so good.

They should look into a little thing called "talent". I know it's not a very popular thing today, but I'll bet you 99 times out of a hundred it's why that older music sounds better than now...

Re:Why so good?

[Myco]

Troll. The question is why old instruments (such as the famous Stradivarius violins) sound so good compared to modern instruments, when played by the same musician. And do you honestly believe that there aren't talented classical musicians out there today? Puh-leez.

Why,

[3-State Bit]

isn't looking at the wave form produced enough? (In terms of matching the same sound in "new form factors", etc.)

Re:Why,

[clearcache]

Well, if you're just looking to reproduce the specific sound, then wave form would be fine. But if you're looking to understand why and how the instruments produce the wave, this helps tremendously:

the XVI instrument offers a "new concept" in vibrometry, as it can measure the rate of phase change at various points of a vibrating object.

Ever notice how a guitar string sound decays and modulates a bit as the sound fades away? We can measure that...and reproduce it...but this lets us look underneath the hood a bit. Of course, depending upon where on the string the pick/finger hits it, and how hard it is struck, it's going change phase at a different rate. They can measure the results of that phase change (in the wave form) now, but an increased understanding of how the material itself vibrates, correlated with the waveform change over time, will bring new understanding to the physics of sound.

Re:Why,

[ripler]

The current version of the instrument produces a line of 16 points, but Morel says that this can be altered according to the needs of a specific application: "It is neither inherently limited to 16 points, or to a linear pattern."

The way a guitar creates the waveform you hear is not only dependant on vibrations in the string, but also resonant vibrations on other strings, the soundboard, back, neck, head, bridge, and nut. Looking at how these components make up the resulting waveform could allow actual Engineering of a classic sound and it's nuances, rather than just a close approximation.

The article also mentions the auto industry as a potential candidate for this technology. Structural Engineering is another that came to mind.

Question

[aster_ken]

Could this technology be used in helping to determine what made violas made by Stratavarius so pleasing to the ear? I know that MRI scans have been done to determine composition of the instruments, but perhaps these types of non-destructive testing could also prove useful.

Let's fall for nostalgia for once...

[pruneau]

They want to know what made these old instruments sound so good.

Well, let me see. In the ol'(which maybe was not so good) time, instruments where done by people who where master of their art, which in turn took years to produce.
They were respected for their unique knowledge, and made apprentice of young people that wanted to learn it. Of course, since making a "proper" instrument was a revered art, it took time as well.

But as time passed, this apprenticeship business losed its appeal for the young generations.
Why ? Because after all it was hard, masters tended to be harsh, brutal and extremely demanding. And they wanted their "secrets" to be closely kept too.
This was eventually replaced by mass industrialisation: producing always cheaper goods with far less dedication and quality, but for everybody to access.

The difference here is clear: current instrument maker simply do not have the same goal and values as past ones.

Is it good, or is it bad ? Who knows, and I'm not the one to start the debate.

But even if they manage to find why a stradivarius is a stradivarius, will they simply be willing to reproduce it truly, and not a scaled-down version of "process" ? I doubt it. Because it might take something that is not only technical. Or maybe those instruments are going to be an elite-thing again.

And in my opinion, there we lose the interest.

Re:Let's fall for nostalgia for once...

[Myco]

Sorry, but no. How much time and love was put into an instrument is not (directly) relevant -- all that matters is its physical makeup. The best instruments today are still painstakingly handmade -- just because there exist mass-produced versions doesn't mean nobody takes the time to produce quality anymore. This is a scientific question about determining in physical terms why one instrument sounds better.

Re:Let's fall for nostalgia for once...

[Myco]

And I don't think that's the case, because we're dealing with scientists rather than craftsmen. Not to say that scientists are somehow better or immune to their own prejudices and conceits, but rather they have different goals. A modern craftsman making a violin is going to work towards an abstract idea of a "good violin," one that sounds good to him and suchlike. This is a subjective process. On the other hand, a scientist attempting to recreate these old instruments has concrete, quantitatively defineable goals that are not so subjective. If we discover what makes these instruments different, the "how" will depend on developing a process which can re-create those qualities. Sometimes good engineering can provide an acceptable substitute for artistry. At the logical extreme, we could have replicators that would produce exquisite instruments without any of the painstaking work put in by old-time crafstmen. There's more than one way to skin a cat, that's all.

Computer cases

[awerg]

How about putting this thing on a computer case and determining how to make it _not_ vibrate?

Then we could get closer to a silent PC without haveing to go to extreme measures.

Beach Boys

[joyoflinux]

The Beach Boys would be so proud :)

Don't they allready have this?

[Cyno01]

Don't they already use something similar to this in some guitars? Lightwave Optical Pickups