I tried using a newer version of Dolphin as Bluekandy suggested, but there was unbearable audio stuttering using roughly the same settings. I also tried enabling audio stretching with a sizable buffer, but that is an unsatisfactory solution for my laptop. I deduce newer versions of Dolphin tie audio to frame rate, which may be the cause of this issue. So, I plan to stay with the version I've been using since the minor graphical issue doesn't really affect my gameplay.