Have you tryed to burn at 2x to see if that would help with sound?
I use UltraISO to burn my Wii games. But i dont have the option to burn with 2 speed. 3 is the lowest i can go. I used IMGBurn with Mario Kart and it wouldnt start. I tried 3 different ISO's. But when i burned the one of the same Mario Kart iso again with UltraISO it worked!!! That's why i prefer UltraISO.
But i am going to give it a try. I'll let you know.
Thnx for the info.