| 摘要 |
PROBLEM TO BE SOLVED: To reduce cost by conducting echo cancellation processing in a hand- free speech such as a cellular telephone system or the like so as to reduce a signal processing scale and an equipment scale. SOLUTION: A received voice signal Sa is sounded from a speaker. A voice St at speech and an echo voice of a voice output (reception voice signal Sa) from the speaker inputted to a TX microphone and its mixed voice signal Se is inputted to a differential amplifier circuit. A delayed reception voice signal Sat obtained by delaying the received voice signal Sa is attenuated by a voice signal attenuation circuit 16 and its attenuation received voice signal Sac is inputted to the differential amplifier circuit. The differential amplifier circuit applies differentially amplifies the mixed voice signal Se from the TX microphone, a voice St from the TX microphone and the echo voice signal of the voice output from the speaker at a same level and on a same time base so as to conduct echo cancellation processing and the transmission voice signal is sent to a transmission section of a cellular telephone set. |
