World’s first sound projector targets willing individuals

Researchers have demonstrated what they believe is the world’s first sound projector, an advance that allows sound to be focused a precisely as light at consenting individuals.

The current version of Sussex’s acoustic projector. The speaker is contained in the back, together with the tracking camera and one of the acoustic lenses. The part in white is the second acoustic lens in the telescope. (Credit: Sussex University)

Dr Gianluca Memoli and his colleagues at Sussex University demonstrated the device in a talk at the 46th International Conference and Exhibition on Computer Graphics & Interactive Techniques (SIGGRAPH 2019) this week.

Dr Memoli, a lecturer in novel interfaces and interactions, 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 is said to work with an in-house face-tracking software which is used to pilot an Arduino-controlled acoustic telescope to focus sound on a moving target.

According to Sussex University, the low-cost 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.

sound projector
(Image: Sussex University)

Joshua Kybett, the second-year undergraduate at Sussex who designed the tracking, said: “Since acoustic lenses can be 3D-printed for only £100, 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 will now expand the capabilities of the sound projector 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.