The most natural form of human communication is speech.
last decades an increasing demand for natural and comfortable speech communication over long distances can be observed and hands-free telecommunication setups are widely used nowadays. Examples for such systems (without claim for completeness) are video-conferencing systems, hands-free front-ends in cars, information terminals, e.g. at railway stations, airports, or public places, smart homes, messaging-software like ICQ c○ or Skype c○ , or computer software and computer games with sound output and speech input. Hands-free systems can be used to increase security while driving a vehicle or to increase communication comfort in teleconference situations. By this, the user of a hands-free telecommunication system may use both hands for other tasks and/or can move freely in a room. Furthermore, the use of a hands-free setup for communication while driving a car is required mandatorily, e.g. by German law since 2001.