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A Sound Discovery

Creating a better guitar pickup

In the course of research, a chance discovery can open the doors to whole new applications of an idea. With a background in physical chemistry and engineering chemistry, Hans-Peter Loock and his colleagues didn't set out to build a better guitar pickup. But while testing a hypothesis for another project, they have done just that.

About eight years ago, Queen's University researchers were building chemical sensors using fibre-optic components. These measure variations in properties of light to determine changes in quantities like pressure or temperature. During their research, the team made another discovery about fibre optics.

"We realized these fibres are very sensitive to vibration," says  Dr. Loock.

This revelation got the researchers thinking about possible ways to test the quality of the sensors.

"I like best that I can pretty much do what I like [with my NSERC Discovery Grant]," says Dr. Loock. "I can think of an experiment and if I have a bit of funding, I can just explore things."

Placing fibre optics on a guitar and listening to the resulting signal is a great way to test their sensitivity. As the strings are strummed, they vibrate the guitar body and the sensors attached to it. Variations in the reflection of light within the sensors are measured and the resulting signal is then converted to sound.

For the sensors to work at their best, it is important that they only detect the vibrations that the user is interested in and disregard all other signals. If they are working optimally, one will hear a pure guitar sound without excess noise.

"If the sensors are good enough for a guitar, then they are good enough for everything else," says Dr. Loock.

To help test the sensors, the team commissioned Niagara on the Lake-based Dagmar Custom Guitars to build an instrument that incorporated the fibre-optic pickups.

Nicknamed "Vicky" after Queen Victoria, the one-of-a-kind guitar has an array of fibre-optic sensors placed on its body. By spreading the sensors to various locations on the guitar, a broader range of sound can be captured with better clarity than with traditional pickups, thanks to their sensitivity. 

At this point in time, guitar players are more interested in recreating the sounds of Jimi Hendrix than forging new sonic ground. Ever since the Beatles opened "I Feel Fine" with a blast of feedback in 1964, fuzzy, squealing guitars have been a hallmark of rock ‘n' roll music. That means traditional guitar pickups—electromagnets with a tendency to produce excess static and buzz—aren't likely to be replaced anytime soon. But the curtain hasn't fallen on the photonic pickup.

"Some companies seem to think our pickup has potential, and we have had conversations with guitar manufacturers. But for that we would have to make it cheaper," says Dr. Loock. "The technique we have now would be competitive for a recording studio but not for an amateur musician."

The other avenue, he says, is as a vibration sensor with an excellent signal-to-noise ratio—a very strong signal and very low noise background. "We know our instrument outperforms commercial sensors that cost from $50,000 to $100,000."

"For example, many modern aircraft are equipped with fibre-optic sensors in their wings, so that pilots can essentially watch the wings vibrate. Those are not acoustic frequencies—the wings vibrate at very low frequencies—but you still need low-noise measurement."

Dr. Loock and his research team are continuing development on the sensor and exploring further applications.