A Portable Acoustic Caption Decoder Using IH Techniques for Enhancing Lives of the People Who Are Deaf or Hard-of-Hearing - System Configuration and Robustness for Airborne Sound -

A Portable Acoustic Caption Decoder enables a person who is deaf or hard-of-hearing to have access to audio announcements in public places if the auditory presentation accompanies embedded transcripts. Despite of discouraging results of studies indicating the low robustness of a signal that is transmitted through the air, our decoder successfully detected signals emitted from a loudspeaker located 77 meters away. Embedded bits were conveyed by white- noise in 16-bits digital (fs=44.1 kHz; 1,411 kbps) at 4 bps using echo-hiding technique. The sound pressure level of the 77-meter point was as low as 46 dB. Autocepstrum diagrams of the point showed that each of the embedded bits keep good "spikes". Although, further experiments are needed, the results will encourage researchers to use "airborne stego-sound" to explore more practical applications.