This tailpiece is coated with a thin-film sensor system. It converts the tension on the string into digital control signals. |
Guitar
virtuosos have to master all kinds of playing techniques. But how can
the intricate process of playing the instrument be captured digitally? A
special thin film on the tailpiece has the answer. Functioning as a
sensor, it converts the tension on the string into digital control
signals.
Rapidly,
but expressively and with amazing ease, the guitarist’s fingers move
over the strings on the neck of the instrument. His fingertips move up
and down and a vibrato resonates. From the guitar a cable leads to a
laptop, which records the virtuoso performance in minute detail. The
computer registers each vibrato, each bend precisely and almost
instantaneously. Afterwards the guitarist can play back the digital
recording and process it on a computer.
The
guitar incorporates a piece of Fraunhofer technology. Engineers at the
Fraunhofer Institute for Surface Engineering and Thin Films IST have
developed a sensor which translates complex guitar-playing movements
into digital control signals.
“This
enables the different techniques such as vibrato and bending to be
precisely captured,” explains Saskia Biehl, head of the micro and sensor
technology group.
The
key element is a thin film bearing the name DiaForce, which coats the
tailpiece, the part of the instrument anchoring the guitar strings to
the body.
DiaForce
is based on amorphous carbon and is piezoresistive. Biehl explains what
this means: “When the player changes the string tension, the pressure
on the film changes. This in turn leads to a change in resistance, which
is measured by electrodes on the film.”
To
be able to record the string tension forces and therefore the various
playing techniques accurately and with as little delay as possible,
Biehl and her group have tested various coating parameters and contact
materials. They achieved good results with a tailpiece coated with a
ten-micrometer DiaForce film. The intention is also to measure the
strength of the string vibration, which would make it additionally
possible to digitally represent the stroke strength and fading –
regardless of whether the player plucks the strings with their fingers
or a plectrum.
The
development partner for this Fraunhofer technology is M3i Technologies
GmbH. The company has already developed a laser-based sensor system
which captures the pitch of chords and individual notes. A software
program converts this data into digital control signals. DiaForce
supplements this development and makes it the perfect sensor system for
guitar playing. The Fraunhofer research engineers now aim to develop
suitable processes for mass producing the DiaForce coating as a low-cost
tension sensor for guitars.
“We
also want to extend its application to other musical instruments,“ says
Biehl. “After all, force is exerted at various points on many string
instruments, and so the possible applications are numerous.”
In
the future, coated tailpieces could replace the pickups on electric
guitars which convert the string vibration into an electrical signal to
create the sound from an electric guitar.
“The DiaForce film will need to be particularly sensitive for this, which is what we are working on right now,” concludes Biehl.
