Is this the end of the keyboard?

Voice interfaces are the solution for places where keyboards break down quickly or alternatively for use in hospitals where the keyboards may serve as a hiding place for bacteria. Tap on the tree

Keyboards are an essential factor in today's computers, but probably not for much longer. A group of scientists used acoustic sensors to turn a tabletop and even three-dimensional objects into a new kind of computer interface.

Sound causing a window to vibrate or passing through a table top is something people experience on a daily basis. Sound waves penetrate through most solid materials. Now researchers from Europe have managed to take advantage of the excellent penetration ability of sound waves through a solid medium to transform everyday objects, including three-dimensional objects into a new type of computer interface.

By connecting sensors to the displayed materials, researchers working in the project known as "Tai Chi" tried to implement a human-machine interface based on acoustics - Tangible acoustic interfaces (hence the acronym TAI). They were able to precisely locate the source of the sounds and follow the acoustic vibrations. Touching certain areas on the board may send musical notes to the computer. Tracking the sound of a finger spelling words on a sheet of wood can be translated in real time into handwriting on the computer screen without the need to insert a layer of a sensitive sensor system under the board.

Sensing the vibrations on a solid medium and turning them into electrical signals is the easy part. The exact location of the vibration source in the solid is the tricky thing. The problem is that the complex structure of the material presented makes it difficult to build a model that will try to describe these fluctuations. Wooden bars inside the table top, for example, will change the distribution of sound waves and vibrations.

The team investigated four main technologies. The time-to-arrival (TDOA) method uses three sensors and compares the difference in the arrival time of an acoustic wave to each of the sensors to locate its location. In fact the concept of TDOA has been around for a hundred years. Given the speed and dispersion of the acoustic wave through a solid material, the TDOA method provides a practical, albeit rather expensive, solution to the problem.

Another method known as time reversal, on the other hand, only needs a single sensor. It works on the principle that tapping at any point on the surface creates a unique impulse that can be recorded and used to calibrate the object. The time reversal method works on XNUMXD objects just as well as on a flat surface.

The third method uses multi-sensor tracking through the Reversal of Dispersion (MUST-RD). This method requires a thorough understanding of the sound scattering properties of the solid material. The dispersion curve of acoustic waves moving on the surface of the material when examining the material is compared to a database of dispersion curves of common materials. From this comparison it is possible to calculate the location of the source of the vibrations, and on this occasion also to estimate at least a rough estimate the type of material.

The fourth method that the researchers of the Tai-Chi project examined is holography in a solid. They used sound pressure, sound compressibility and its speed in the solid medium to calculate position and time. In this way, the sound source can be mapped and simulated in the same way that infrared cameras are used to map a heat source. Some of the researchers also experimented with a combination of acoustic positioning and tracking using the Doppler effect to locate and track a sound source moving through the air.

The group included researchers from Germany, France, Italy, the United Kingdom and Switzerland and was partially funded by the European Union, led by Dr. Ming Yanek of Cardiff University in Wales, United Kingdom.

According to Ming the voice sensor interface should not replace keyboards and mice in the near future, but in specific environments where keyboards are not useful - for example in dirty environments or alternatively in hospitals where the keyboard could be a hiding place for bacteria, TAI systems can provide an elegant solution. He especially likes the time reversal solution, unlike TDOA, it works on any bone and doesn't require special materials. Since it only needs one sensor and a normal computer, it is simple and cheap. A spin-off company of the University of Paris is currently working on commercializing applications using this method. Other technologies such as acoustic holography have shown great promise but are not ready for commercialization.

CeTT, a company from Switzerland that is a partner in the consortium, assembled a development kit for TAI that includes algorithms developed during the project, software and hardware in one package for application developers who wish to implement the breakthroughs of the Tai-Chi project. Among the applications - wireless sensors using Bluetooth technology that Yang would like to develop together with partners from the industry. "Time reversal technology is an important breakthrough" says Yang. "Previously, people only worked with light materials, now we have developed the ability to absorb sound waves passing through plastic metals and plates and we have a real interactive interface.

For information on the ICT REPORT website