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

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.

Don't they allready have this?

[Cyno01]

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