Do you have the CPU governor set to performance mode? If not, switching to it will certainly help.
I remember running into occasional audio crackle in SwanStation even with the performance governor though. Maybe there are other tweaks someone can post to fix that 
I took the lazy route and went back to PCSX-ReARMed. It runs much better on these devices, and I can’t say I’ve noticed any major accuracy problems (no doubt they do exist for some games though).