| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive speech unit capable of canceling an audio component emitted by a speaker from a transmission signal over a wide frequency band, thereby preventing the occurrence of howling. SOLUTION: After the lapse of a delay time with respect to a sonic wave of a frequency f1 from a timing when an A/D conversion circuit 30 performs A/D conversion on an audio signal from a microphone M1, an A/D conversion circuit 31 performs A/D conversion on an audio signal from a microphone M2. While defining as deviation times Th2-Thn a phase difference in components of frequencies f2-fn with respect to a component of the frequency f1 in audio signals collected by the microphone M2, based on an output of the A/D conversion circuit 31, an inference circuit 322-32n infers the audio signal outputted from the microphone M2 in the timing deviated from the timing when the A/D conversion circuit 31 performs A/D conversion, by the deviation time Th2-Thn, and audio from a speaker SP is reduced via attenuation circuits 351-35n and an arithmetic circuit 36a. COPYRIGHT: (C)2008,JPO&INPIT
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