Author(s): Georgios Mantokoudis * , Claudia Dähler, Patrick Dubach, Martin Kompis, Marco D. Caversaccio, Pascal Senn
For many years the use of videophones for transmission of sign language or lip motion over telephone networks was either expensive or of low image quality, thereby limiting its use . Short message service (SMS), instant messaging services or teletypewriters have therefore become the main long-distance communication modes among hearing-impaired and deaf individuals in the last two decades . Written communication, however, is usually slower and less ideal to transport emotional content compared to audio-visual (AV) communication. The relative lack of long-distance communication options among hearing-impaired and deaf individuals contributes to a reduction of social connectivity and is associated with increased morbidity and mortality , . Recently, Internet infrastructure and communication software tools have been rapidly developing and now allow both audio and audio-visual Internet communication with ever-improving quality. In comparison to conventional telephony, Internet telephony also offers broader sound frequency ranges and improved conservation of audio quality. These technical advantages of Internet over conventional telephony have translated into improved speech perception by hearing-impaired and normal hearing adults in recent, laboratory-based studies by our group , . Earlier studies were limited to transmission of audio signals through Internet telephony, and to our knowledge, no reports on speech perception with Internet transmission of audio and visual content have been published. The current study aims to address the value of added visual content. There is evidence that cochlear implant (CI) users improve speech perception performance if visual cues are presented together with an auditory input -. In addition, CI users maintain their speech reading capacities after implantation -.
Video telephony as provided by Skype[TM] and other Internet communication companies offer a broadband transmission of voice and image over an Internet protocol (IP) network. The Internet software sends small packets of encoded data over the Internet guided via the IP. Each data packet takes a unique pathway through the network before arriving at a receiver computer that uses the same software as the sender. The receiver's software then collects, reconstructs and decodes all data packets before finally converting them back into an analog signal that is presented to the end-user.
Despite its potential benefits, the quality of internet video telephony transmission may be hampered by congested internet lines , inadequate infrastructure or insufficient bandwidth, which lead to data packet loss or delay, frame rate reduction, audio-visual asynchrony , or decreased signal-to-noise ratio of the video signal . The web camera properties (lenses, resolution, camera software) may also influence video quality. To what extent these parameters influence speech perception, particularly by hearing-impaired individuals, has not been sufficiently addressed. Additionally, the potential of rapidly-improving Internet communication technology for helping hearing-impaired individuals remains largely unknown. The first aim of this study was therefore to test the hypothesis that current Internet technology allows sufficient transmission of lip and face motion images for adequate speech reading. The second aim was to assess the range of parameters within which visual contributions are...