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New sensor digitally captures complex guitar-playing movements


July 12, 2011

Researchers have coated a guitar tailpiece with a thin layer of DiaForce, which allows for accurate digital capture of complex playing movements (Photo: Fraunhofer)

Researchers have coated a guitar tailpiece with a thin layer of DiaForce, which allows for accurate digital capture of complex playing movements (Photo: Fraunhofer)

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For most of us, digitally capturing our six-string virtuosity involves plugging an axe into a guitar interface like Apogee's JAM and then launching some software on a laptop or mobile device. Researchers from Germany's Fraunhofer Institute for Surface Engineering and Thin Films are currently developing a somewhat neater, and potentially more accurate, solution that also holds the promise of replacing the humble guitar pickup. The guitar's tailpiece has been thinly coated with a contact material which is claimed to precisely capture complex playing movements in minute detail and convert them to digital control signals for onward processing.

The thin film coating on the tailpiece acts as a sensor to convert string tension into digital signals. Working with M3i Technologies, the researchers tested numerous coating parameters and contact materials before settling on a ten-micrometer coating of DiaForce - an amorphous carbon-based material that's also piezoresistive - which appeared to produce the best results, accurately capturing the subtle phrasing produced by the player (from gentle vibrato to stinging bends or lightning fast progressions) in something very near to real time.

"When the player changes the string tension, the pressure on the film changes," says Saskia Nina Biehl, head of the micro and sensor technology group. "This in turn leads to a change in resistance, which is measured by electrodes on the film."

The engineers are also looking to record the strength of a string vibration using the system - to digitally represent the strength of a player's stroke and the fading of the note, regardless of whether the player is using a pick or fingers.

Supplementing an earlier development where data from laser-based sensors are converted into digital representations of chord pitch and individual notes by specially-developed software, the project is now heading towards commercialization as a low-cost tension sensor for guitars and other stringed instruments.

It's also believed that, with some sensitivity tweaking, the technology could go on to completely replace pickups on electric guitars.

The following short video shows the string tension system in action:

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Paul Ridden While Paul is loath to reveal his age, he will admit to cutting his IT teeth on a TRS-80 (although he won't say which version). An obsessive fascination with computer technology blossomed from hobby into career before the desire for sunnier climes saw him wave a fond farewell to his native Blighty in favor of Bordeaux, France. He's now a dedicated newshound pursuing the latest bleeding edge tech for Gizmag. All articles by Paul Ridden
1 Comment

It\'s pretty smart and Fraunhoffer is a very innovative research center but I have doubts about it. I suppose it works only well to reproduce the same type of sound of the traditional pickups, if the whole signal chain is remodeled digitally (and it\'s still doubtable quality, I tried those Line6 axes with built in modeling, for some tones it\'s pretty impressive, but experienced ears could hear the difference sometimes to notice the \"faked\" sound.) Also using more and more digital modeling devices in the chain will led to some unexpected weird phenomena coming from the digitezed and digitally generated output that you can\'t find in the analog signal propagation. Of course, traditional electronics have their own drawbacks, too.

Anyway, very interesting try and could broaden the sound collection for guitars, but I hardly believe that it could replace the traditional way soon. For addition to it will be pretty cool!

Iván Imhof
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