Speakerphone and microphone case for the same

摘要

A speakerphone of the present invention can obtain an output in which an acoustic coupling component between a louder speaker and a speech microphone has been removed. The loudspeaker telephone set of the present invention comprises a noise canceling microphone 25 which is located near the speech microphone 6, a band-pass filter amplifier 26 for extracting only a partial frequency component of a signal from the noise canceling microphone 25 and a differential amplifier 27 for adding a signal extracted by the band-pass filter amplifier 26 in opposite phase to a signal from the speech microphone 6 so that an acoustic coupling component between the louder speaker 4 and the speech microphone 6 is canceled by the result of the above addition.