Tangible sound

17.05.2011 22:11

A week ago Miha Ciglar from Ultrasonic audio technologies stopped by Zemanta's new office to demonstrate the tactile user interface technology they are developing. Before we met him none of us knew this kind of development is done in Slovenia, much less practically next door. We were all curious what exactly tactile ultrasonic interface means so we invited him to show one of his prototypes to us.

You might have caught the recent article about the so-called multitouch force field presented last week in Vancouver by Texas A&M University students. If you read past the science-fiction inspired title you see that it is basically only an infrared virtual-barrier type of device. It might detect accurately the position of your fingertips in the middle of the air via beam-break sensors, but there is no touch or force involved.

Miha Ciglar demonstrating a prototype tactile ultrasound interface

On the other hand the technology from Ultrasonic audio promises that you might one day actually feel parts of the computer user interface floating in space. They achieve this via focused ultrasound. This prototype uses standard piezoelectric transducers in a fixed parabolic arrangement and can radiate around 7 W of power at 40 kHz. Of course, you can't hear those frequencies, much less feel them. But through amplitude modulation of the ultrasonic carrier wave you can achieve tactile effects.

While the focused beam is invisible and inaudible, it can have some quite macroscopic mechanical effects, as Miha demonstrated with a piece of paper. I guess you could call this a textbook demonstration of the fact that waves carry momentum.

I admit that after seeing that it took some mental effort to put my hand where the paper leaflet was in the video. The effect on my fingertips however was much less dramatic. I couldn't feel the upwards push - it felt more like wind was blowing over my skin. Perhaps the intense oscillations in the air cause faster evaporation of sweat from the skin? Miha explained that with some settings you can also feel heat, when sound wave energy is converted via friction. I opted not to try that one.

One interesting side effect of this research into tactile interfaces was the discovery that such an intense, focused beam of ultrasound exposes non-linear nature of adiabatic processes in the atmosphere. This means that the amplitude modulated carrier wave can demodulate itself in thin air. The result is a speaker that produces sound that appears to originate well away from its real source.

It might look like nothing special, but when Miha swung the parabola around and moved the focus around the room the effect was uncanny. The soundtrack of people speaking didn't help with the feeling. If you can move around you can localize the sound source pretty well and it's quite amazing to find out that you can't see anything there.

In conclusion, the effects are pretty amazing and while promising, I'm guessing this technology still has some way to go before it goes mainstream. Safety is certainly one concern. From my own experience with ultrasound I know you can find some pretty loud emitters on every step, but this works on a completely different level. I'm not usually shy around sources of electromagnetic radiation of various wavelengths, but during this presentation I couldn't help but picture early researchers wondering at pretty flashes in radium and not knowing about what the invisible rays are doing to their bodies.

Posted by Tomaž | Categories: Life

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