| 摘要 |
PROBLEM TO BE SOLVED: To exchange information without disturbing listening of sound. SOLUTION: A modulation apparatus generates a waveform obtained by combining a plurality of frequency components. When superimposing information on the waveform, the modulation apparatus changes factors (frequency values or levels) of respective frequency components in accordance with encoded information. In a case where there are a waveform represented by combining frequencies f<SB>0</SB>, f<SB>1</SB>, f<SB>2</SB>and f<SB>3</SB>, for example, when superimposing a code stream "101", the modulation apparatus shifts the frequency f<SB>1</SB>just by Δ<SB>1</SB>, shifts the frequency f<SB>2</SB>just by Δ<SB>0</SB>and shifts the frequency f<SB>3</SB>just by Δ<SB>1</SB>. Namely, when a case where no shift is performed is defined as a criterion (a), the modulation apparatus combines waveforms of frequency components obtained by shifting respective frequencies from a criterion value just by values corresponding to the code stream (b). COPYRIGHT: (C)2010,JPO&INPIT
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