An echo removing apparatus for reducing the echo caused by sound returning
from a speaker to a microphone of a small-sized communication terminal,
such as a portable telephone. The echo removing apparatus includes a
filter unit for outputting a pseudo echo signal estimating an echo
component returning to the microphone based upon a generated sound signal
supplied to the speaker, a subtractor for subtracting the pseudo echo
signal supplied from the filter unit from the sound generated collection
signal supplied from the microphone and a first characteristics
conversion unit for converting frequency characteristics of sound
generated collection signals from the microphone on the frequency axis.
The characteristics of the filter unit are controlled for minimizing an
error component between an output signal of the first characteristics
conversion unit and an output signal of the filter unit.