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Touch sound localisation technology

A team from the Korea Advanced Institute of Science and Technology (KAIST) has developed a smartphone-based touch sound localisation technology that can turn objects like furniture and mirrors into touch input tools.

The technology is able to analyse touch sounds generated from a user’s touch on a surface and identify the location of the touch input. The researchers said that users will be able to turn surrounding tables or walls into virtual keyboards and write lengthy e-mails much more conveniently by using only the built-in microphone on their smartphones or tablets.

In addition, more traditional smart devices, such as smart TVs or mirrors, which provide relatively simple screen display functions, will now be able to play a smarter role by adding touch input function support.

The most important aspect of enabling the sound-based touch input method is to identify the location of touch inputs in a precise manner (within about 1cm error), but this can be challenging as environmental changes can affect the characteristics of touch sounds.

To address this challenge, Professor Insik Shin from the School of Computing and his team looked to analyse the fundamental properties of touch sounds, especially how they are transmitted through solid surfaces.

On solid surfaces, sound experiences a dispersion phenomenon that makes different frequency components travel at different speeds. Based on this phenomenon, the team observed that the arrival time difference (TDoA) between frequency components increases in proportion to the sound transmission distance, and this linear relationship is not affected by the variations of surround environments.

Based on these observations, Research Assistant Professor Hyosu Kim has proposed an innovative sound-based touch input technology that records touch sounds transmitted through solid surfaces, then conducts a simple calibration process to identify the relationship between TDoA and the sound transmission distance, finally achieving accurate touch input localisation.

Test for accuracy has found that the average localisation error was lower than about 0.4 cm on a 17-inch touch screen. Particularly, it provided a measurement error of less than 1cm, even with a variety of objects such as wooden desks, glass mirrors, and acrylic boards and when the position of nearby objects and noise levels changed dynamically. Experiments with practical users have also shown positive responses to all measurement factors, including user experience and accuracy.

Professor Shin said, “This is novel touch interface technology that allows a touch input system just by installing three to four microphones, so it can easily turn nearby objects into touch screens.”

Neil Tyler

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