Researchers at Bristol University have developed a new system that simulates the feel of objects in mid-air using nothing but sound.

The “UltraHaptic” system uses an array of ultrasonic transducers – a grid of small piezoelectric speakers that produce waves of ultrasound, the same as those used to scan babies in the womb – which align to produce an invisible layer of ultrasonic vibrations in the air above a display. This creates a small tactile sensation on the surface of human skin.

Haptic feedback, as techniques like this are known, is the process of creating a tactile sensation for virtual objects. For instance, some smartphones vibrate on virtual button presses, while others emit audible keypad tones while dialling numbers.

“By creating multiple simultaneous feedback points, and giving them individual tactile properties, users can receive localised feedback associated to their actions,” said Tom Carter, a PhD student in the Department of Computer Science's Bristol’s Interaction and Graphics group.

Virtually interact with objects in mid-air

The array is placed behind an acoustically transparent display that monitors the motions of a user’s fingers above the screen, providing a tactile feedback layer as they virtually interact with objects like knobs and switches in mid-air.

UltraHaptics allows a user to experience a tactile interaction with virtual objects in mid-air.

The ultrasonic layer can also be used for mid-air gestures, as well as allowing the user to identify different tactile properties without actually touching anything.

“Current systems with integrated interactive surfaces allow users to walk-up and use them with bare hands. Our goal was to integrate haptic feedback into these systems without sacrificing their simplicity and accessibility,” explained Carter.

Several systems, including Microsoft’s Kinect sensor and the LeapMotion, have pushed technology which monitors a user’s hand and body motions to allow them to interact with a computer interface, but have lacked any sort of feedback, bar audio and visual alerts from a display screen.

The research paper is to be presented at the ACM Symposium on User Interface Software and Technology 2013 in St Andrews on Friday by Carter.

• Senseg, among others, are working on bringing haptic feedback to touchscreens by giving them 'texture' through the use of electrostatic forces.