Sound projector beams audio to a moving person and no one else can hear it

Sound projector developed at University of Sussex
Credit: University of Sussex

A sound projector that tracks and delivers audio to moving individuals has been dubbed “the audio equivalent of special effects”.

The invention comes out of the University of Sussex in the UK. A research team from the university demonstrated the system at the Siggraph conference last week in Los Angeles, USA.

Led by Dr Gianluca Memoli, the team showed off what they claim the world’s first sound projector with an autozoom objective.

Dr Memoli, lecturer in novel interfaces and interactions at the University of Sussex’s School of Engineering and Informatics, said: “By designing acoustic materials at a scale smaller than the wavelength of the sound to create thin acoustic lenses, the sky is the limit in new potential acoustic applications.

“Centuries of optical design can now be applied to acoustics. We believe this technology can be harnessed for plenty of positive applications including personalised alarm messages in a crowd, immersive experiences without headphones, the audio equivalent of special effects.”

The system works with an in-house face-tracking software which is used to pilot an Arduino-controlled acoustic telescope to focus sound on a moving target.

An off-the-shelf web camera is able to track a person and command the distance between two acoustic lenses, delivering a sphere of sound around 6cm in diameter in front of the target, which then responds to the individual’s movement.

Joshua Kybett, the second-year undergraduate at Sussex who designed the tracking, said: “Since acoustic lenses can be 3D-printed for only £100 [approximately €108], we wanted a tracking technique that worked on a similar low budget. With a £10 webcam, this is one tenth of standard tracking systems.

“In addition, our method has been designed to require user consent in order to function. This requirement ensures the technology cannot be used intrusively, nor deliver sound to an unwilling audience.”

Thomas Graham, the research fellow in the School of Engineering and Informatics who ran the measurements and the simulations, said: “In our study, we were inspired by autozoom cameras that extend their objectives to match the distance of a target. We used a very similar system, with even the same mechanical sound of the motor. I believe our work is also the first step towards hand-held, low-cost acoustic cameras.”

The research team are now working to expand the capabilities of the system beyond tracking for just one direction and over one octave, to ensure it can be scaled up to cover most speech and basic melodies and eventually to deliver a full piece of music.

Arash Pouryazdan, who designed the electronics, said: “Siggraph is a place where emerging and futuristic ideas are discussed. This is the conference where entertainment giants such as Disney, Marvel and Microsoft meet to share their visions: it was the perfect place for us to demonstrate how we think sound might be managed in the future.”