Just was curious, but why is it that when sound is disabled the games have a potential to be at full speed?

idk maybe because its not taking the extra time to emulate the sound

But why is it that the frame rate drops when its enabled? I never understood that with emulators.

sound takes work to emulate so if you enable the emulation its going to slow down the emulator

is easy to answer!

example (with your body) XD

if your body needs breathe the request of function "take a breath" needs to be processed by your brain (Processor) this take a little of time (some people say "this process is automatic")... but anyway coordinate this needs a tiny fraction of a second (time) and resources (minimums)

now... obviously... you need coordinate many more things to live! XD... per example, hearing, sight, touch, language, this are primary and important processes but it turns complicated when your brain needs coordinate your memory, your movements, your mind, your language, and anything else because your brain has to process more actions at the same time and coordinate it all, fortunately our processing capacity is not limited like a "machine" but for a machine this is a problem because don´t have the "enough power" to do many things like us, and here comes the typical problems. craches, overheating, errors, and curses! XD.

the frame rate drops when we activate the sound because our psp now has to run other function, has to coordinate the video with the sound (synchronize both), and obviously this takes a lot more time to be processed and coordinate than if only was just the video because don´t has to decode the sounds (video emulation need a lot resources to be decode, and if you turn on the sound too... you would be forcing more the processor but the processor of the psp is very limited) XD, do you understand?

"Sorry for my bad english, I´m mexican"

Indeed. Just has you have to stop breathing, talk, then breath again, the emulator would have to stop, emulate the sound, then continue. Bad analogy I guess. But sound just puts more strain on the processor. The PSP has a pretty weak cpu, which clocks in at 333mhz, and it's gpu is only 166mhz. When adding extra strain to that it causes slow downs. What the devs do to speed up the emulator in general is find optimizations and spots of code that they can change to relieve stress on the cpu.