Sound Activated LED Mod How-to from Acid Mods
Over on the Acid Mods wiki there is now a guide on how to add sound activated shoulder button LEDs to the PSP. This mod was originally created by CyberPyrot and F00 f00 to use headphones or external speakers but then evolved, in response to a mass of emails, into a solution that uses the PSP's internal speakers. This does involve disassembling the PSP (voiding the warranty) and requires advanced soldering skills. If you choose to do this then realize that you are doing so at your own risk. With that said, this is not one for beginners but if you're still interested then you can head over to the Acid Mods wiki article using the link below. Also below is a picture of what the chip looks like after it's been put together.
Acid Mods' PSP Sound Mod
Source:
Acid Mods