| 摘要 |
<p>PURPOSE:To prevent the echo, by always adding the reference signal having a certian spread of frequecy to the driving side of an electro-acoustic transducer to extract the reference signal entered the electroacoustic transducer and then detecting the degree of acoustic coupling to erase the reference signal entered the transducer. CONSTITUTION:The aural signal supplied through a telephone receiver terminal 7 is amplified 8 and 9 to be delivered through a speaker 2. The voice, etc. supplied through a microphone 1 is delivered through a transmitter terminal 6 via amplifiers 4 and 5. A reference signal generator 10 produces the signal BG music, etc. having a certain frequency spread to add it to the amplifier at all times and then to deliver it throuth the speaker 2 in the form of a sound wave. This sound enters the microphone 1 to be extracted by a detector 11, and the amplitude and the phase are compared with the reference signal 10 through a comparator 12. As a result, a tap gain controller 14 is controlled to control the tap output signal of a delay circuit 13. Thus the signal corresponding to the entering characteristics is erased. As a result, the coupling state is detected to erase the entered signal although the environment varies.</p> |
