yaantey:
About the diagram. I want the voice from microphone to go arduino and check the frequency or voltage range and if its between a certain range to on the speaker and output from the voice from the speaker. Is it possible with the block diagram you mentioned.
That doesn't make sense to me. What I think you mean is that the speaker should normally be silent, but when the sound picked up by the microphone is loud enough, the signal from the microphone is amplified and fed to then speaker. In which case, this circuit can do that of the Arduino is suitably programmed. The Arduino will take a small amount of time to decide that the signal is loud enough, so the speaker won't cut in until a few milliseconds after the loud sound started. This may make it hard to understand what the first word spoken was.