groundFungus:
Re-read reply #2. Another choice is to clean up the power supply (Vcc) so there is no noise to inject.
I did not understand. I think the R1 can't be removed, because electret mic needs some voltage biasing in order to work. Apart from power supply noise I think there is another being caught from environment. I need to cure that as well. Any help on that would be appreciated.
Thanks,
Debojit