| 摘要 |
PROBLEM TO BE SOLVED: To provide a modulation device for drastically reducing noise by simple processing and having few restriction during communication, a demodulation device, an information transmission system, a modulation method and a demodulation method. SOLUTION: In the information transmission system, as for the modulation device, a component of an input audio signal Sa is removed, and a part of frequency band component of a remaining frequency band is superimposed with the removed frequency band by frequency shifting with a shift amount corresponding to coding information of transmission information, and thereby sound of a modulated modulation audio signal Se is output. As a result, even if the modulation audio signal Se which is output at information transmission time is heard, uncomfortable feeling for sense of hearing by modulation is reduced. At this time, as an output level of an audio signal Sd which is frequency shifted is adjusted to get a frequency distribution closer to that of the original audio signal Sa, the uncomfortable feeling for sense of hearing is further reduced. COPYRIGHT: (C)2010,JPO&INPIT |
