How about this link sir?

http://www.extremenxt.com/sound.htm

the creator of the project said that the circuit is a simple sound sensor but I can't quite figure out the purpose of the diode array with the label RCX. I tried to look for a way to contact the creator of the project but I didn't find any. I know that the circuit is made for RCX from Lego Mindstorms, but I just want to know how to use this sensor for a PIC, specifically 16F84A, so that I could make a PBP program for my project. Any help would be gladly appreciated. Thanks in advance.