I'm a novice, I don't know much about electronics, but I'm enthusiastic and looking to learn....

I'm trying to find an audio activated circuit like one of those whistle key chains where a loud noise activates the circuit.  I've taken one a part, but there appears to be some sort of surface mounted small IC covered in black epoxy rather than mounted as a chip (four pins, no casing)

Any ideas where I could learn how to build a simple circuit like this, I'd like one that lights up when activated by noise instead of beeping.

Thanks in advance,
Peter