L LAST INCH-INPUT AND OUTPUT TECHNOLOGIES TOUCH INPUT When words fail people, they often resort to touch. A comforting hand on the shoulder or, in dire situations, a sock to the jaw can express a person's inten- tions and feelings quite adequately. Touch can also be used to input various types of information on computers and many types of mobile devices. Imagine, for example, ordering your meal in a restaurant by a simple tap on the table, which would transmit your choice directly to the kitchen. Or how about placing an order for goods by making your selection on the surface of the shop window? It may sound like science fiction, but this could be the way we interact with computers in the future, thanks to a pan-European research project, led by experts at Wales' Cardiff University. "The vast majority of us communicate with our computers using tangible interfaces such as the keyboard, mouse, games console, or touch screen," says Ming Yang of the University's manufacturing engineering center. "Although these are in common usage, they have certain disadvantages-we are required to be 'within reach' of the computer, and most devices lack robustness to heat, pressure, and water, restricting their spheres of application. Although some voice-activated and vision systems for interacting with computers do exist, they are as yet unreliable." The research project's goal is to develop Tangible Acoustic Interfaces for Computer Human Interactions (TAI-CHI). It will explore how physical objects such as walls, windows, and table tops can in effect become giant three- dimensional touch screens, acting as an interface between any computer and its user. The whole project is based on the principle that interacting with any phys- ical object produces acoustic waves both within the object and on its surface. By visualizing and characterizing such acoustic patterns and how they react when touched or moved, researchers can develop a new medium for commu- nication with computers and the cyber-world. Although acoustic sensing techniques ha