Electronic Design

Hot Hands For Some Cool Rock: Motion Sensing Meets Audio Engineering

As an electric guitarist and rock aficionado, I was excited to see the recent announcement of a new company developing motion-controlled guitar effects—Source Audio, with its debut product, the Hot Hand controller.

Hot Hand embeds an accelerometer into a ring you wear on your picking hand. A control box allows you to dial in various "wah" filters and frequencies, and a sensitivity control determines the effects via picking, strumming, or "flailing." (Flailing would be the perfect setting for Who guitarist Pete Townshend, famous for his windmill power chords.)

Source Audio's founders are former Analog Devices (ADI) engineers Jesse Remignanti and Roger Smith. They hatched the idea for motion-controlled effects during an ADI technical conference where tabletop exhibits fortuitously positioned digital audio engineers next to the accelerometer product team.

The engineers started brainstorming—then experimenting. When they decided to launch a company, they recruited Bob Chidlaw, formerly chief scientist at Kurzweil, to help them refine the digital musical effects. "We decided that incorporating an accelerometer would give us a way to really differentiate our products, to stand out from the crowd," Remignanti said.

Hot Hand uses ADI iMems sensors, initially developed for airbag deployment back in 1991. Since then, over 200 million ADI airbag sensor devices have been sold, driving down their cost to a point that is attractive for use in the effects controller. For Source Audio, the ADXL320 sensor offers low power in a small package, which makes it ideal for incorporation in the pick-hand ring.

Other companies have tried motion control for guitars, says Remignanti, "but no one has done it effectively, until now." Combining the accelerometer with an Analog Devices SigmaDSP offers a unique solution. The DSP couples a 56-bit audio processor with 24-bit analog-to-digital and digitaltoanalog converters for a 100-db dynamic range.

Source Audio initially tried embedding the accelerometer in a guitar but discovered that the motion response range was better suited to wearing it on the hand. Plus, the ring has a glowing blue LED that adds an extra cool touch on stage!

Remignanti and Smith loaned me a prototype Hot Hand unit, and I loved my test drive. When it comes to guitar effects, this is a great new approach. On the most sensitive picking and strumming settings, the ring could translate the motion of my regular rhythm-guitar style into perfectly synchronized wah effects. What's more, the ring allowed me to experiment with new "in air" hand movements and playing techniques to manipulate sustained tones.

But once Hot Hand products are put into the hands of true axe masters, things will really heat up! My favorite guitarists favor a "whole body" playing style. They follow a path blazed by Jimi Hendrix, positioning the guitar, amplifier, and themselves so they interact to create a feedback-enriched sonic zone where every dip and turn of guitar and player alters a wall of sound.

Critics who say gyrating rock guitarists are just posturing don't understand this amazing interplay of body, emotion, and electronics. I most recently encountered this style of playing at an Audioslave concert. The group's guitarist Tom Morello is a master of this technique, and he truly blew me away. If you love rock guitar, check out Audioslave and watch this guy play!

Remignanti was reluctant to tip his hand (pun intended) about what other sorts of sensors or technologies might join the accelerometer. But he says there are some more tricks up his sleeve (pun intended again).

The unique design concepts that were jumpstarted when iMEMS managers started talking to audio engineers is a great example of the sort of cross-discipline creativity that underlies our goal as a publication. With our reach to electronic engineers in many different vertical markets, it's always interesting to imagine your differing perspectives when you read our new technology coverage. Our hope is that Electronic Design is a key springboard for you to keep the creative design juices flowing. Rock on!

To read more about my conversation with Remignanti and to listen to an MP3 of my original song "Accelerometer," incorporating the new effects, go to www.electronicdesign.com and see Drill Deeper 12518.

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