Freetel – Esprit

Start Date: 01/01/1992
End Date: 31/12/1994
Project Leader: Carayannis George

The project aimed at the design and creation of high quality hands-free telephone communications, optical-acoustic systems and mobile-phones. Research includes the improvement of acoustic modification based on environmental characteristics, the design of an efficient echo reducer, the techniques for noise reduction and the provision of the best hands-free communication processing solutions which are adaptable to each application.

In more detail, the project covered the following areas:

  • Improvement based on the definition of each application environment, selection of the appropriate microphones and location of the best positioning in the vehicle for the microphone and the loud speaker.
  • Echo reduction: Important improvements in this field are expected, regarding efficiency and user-friendliness. Multiple zone techniques with effective filtering methods and new non-linear techniques were also studied.
  • Noise reduction: Techniques in the field of time (adaptation filters) and the field of frequency (optimised spectral subtraction) as well as algorithms based on higher class statistics so as to ensure an improvement of communication quality in noisy environments.
  • Overall improvement and complication reduction methodologies led to the design of an appropriate solution for each acoustic environment.
  • Creation of a real time prototype for vehicles, this being the most difficult application of its kind.