The magic of sound

Holograms (3-D light fields) can be projected from a 2-dimensional surface to control objects. Credit: Asier Marzo, Bruce Drinkwater and Sriram Subramanian

Asier Marzo, PHD student and lead author, levitating a polystyrene ball with soundwaves.

Ever heard of “Tractor Beams”?  Those were use in Star Trek to move objects with no use of ropes and pulley through some magic force acting at a distance.

But those were  figments of the imagination of screen-players and their effects were nothing more than “special effects”.

We have ways of controlling objects from a distance, moving, rotating and levitating them through magnetic fields. But you need a magnetic sensitive objects for the magnetic field to have any effect.

Now  researchers at the University of Bristol and Sussex in cooperation with Ultrahaptics have managed to create sonic holograms, waves of sound that are focused in space, and to use these sound holograms to move, rotate and levitate (small, light) objects.

I remember the time we used focused sound waves at the Future Centre of Telecom Italia in Venice to create small space bubbles in the courtyard where roamers got to hear Christmas carols. They could hear the music in one spot and jus a meter away it was complete silence.  I still remember the surprise on the faces of people visiting us.

What researchers have done with sound holograms is to move a step forward. In our case it was just a matter of focusing sounds by recomposing sound waves in a specific, small, area. Here the trick is similar but it requires a greater control of the sound waves with much higher strength. 

It is like creating a shroud enveloping the object. The sound waves create pressure points that can push the object. In their demonstration they have used  64 miniature loudspeakers controlled by a computer to create the hologram around a small sphere of polystyrene. By controlling the various sound waves one can put pressure on one side of the object and decrease pressure on the other side resulting in the motion of the object from the high to the low pressure areas.

The researchers expect to be able to increase the “coherence” of the sound hologram and hence to increase the size and weight of objects that can be manipulated, aiming at controlling a soccer ball from a distance of 10 meters. As practical application they see this tractor beams in use in production / assembly od delicate components that will be moved without the need of touching them. Also, they imagine sound tractor beams applied to move drugs and micro surgical instruments inside a human body.

Really, there is always something new coming up! Who said that everything has already been invented?

Author - Roberto Saracco

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