entral server and from the server to the user. A microphone-equipped headset and voice-recognition and synthesis softwares supply the user interface. With the use of visual markers provided by the mobile camera, as well as localization software, the server automatically calculates the user's exact posi- tion and orientation. "He or she can walk around the workplace, point the camera at the object, and ask how it is," says Navab, who's an imaging and visualization project manager at Siemens Corporate Research in Princeton, New Jersey "One simply says something like, 'Current status." The server will then query the object and divulge the item's current operating condition- temperature, pressure, voltage, flow rate, and SO on. The user can then request specific historical information about the object, such as its model number, age, service history, and the name of the employee directly responsible for its main- tenance. The user can also leave a voice message that will be supplied to the next person who talks to the object. Navab believes that the technology could be used in a wide range of fields. "Factories, power plants, refineries-any place that might have thousands of different pieces of equipment," he says. Siemens is testing the system with a variety of different wearable and mobile computers, and a pilot version is being installed at a working industrial facility. 9.2.3 Computer Talk When using speech-based interfaces on mobile phones and other devices, people not only talk to a computer, they often find themselves talking like a computer-a finding that could be crucial for researchers designing mobile audio interfaces. Researchers at Oregon Health & Science University in Portland, Oregon, have discovered that people who converse with text-to-speech (TTS) com- puter systems substantially change their speech to sound like the computer- a phenomenon known as speech convergence. Additionally, people tend to readapt their voice to each new computer-generated voice they hear. "Human speech is always a variable," 