A student asked about the assignment, and I suggested using subjective sound. She responded:
Alright, so to show my ignorance I had to ask 3 kids in our class to confirm my definition of subjective sound and none of them could quite define what it is. I'm guessing it refers to non-diegetic sound, something that isn't necessarily related to the picture but evokes an emotional response? Am I way off?
From Lecture 1:
Subjective sound - using the wrong sound for the right (emotional) effect, even if it is completely illogical. Frequently it is layered with reality-based sounds and/or played at a subliminal level.
So yes, it could be considered non-diegetic. A good example would be the earthquake-like rumble in the Oval Office scenes in Oliver Stone's NIXON. Not at all logical, but very effective.