need some assistant on the op-amp circuit attached in the thread.

yaantey:
Thanks alot. Can I use the above circiut to drive a small speaker? Which is 0.5 W and 8ohms?

You mean use the circuit to amplify the signal from the microphone and drive a speaker? You can try it, but it won't be very loud. The LM358 is a low-power op amp so it is only designed to source or sink a few milliamps.