I tinkered with that a while back. Night mode only works with Dolby Digital soundtracks according to the manual, so it wouldn't do anything with a DTS DVD. When I tried to figure out exactly what night mode was doing, I found that each level of night mode appeared to reduce peak sound levels by ~2dB. That was tested using the opening salvo of the early sea battle scene from Master and Commander set on A-B repeat with my SPL meter sitting on the couch.