mclovin is right, that Dynamic Volume == dynamic compression. The overall volume is boosted, so peaks are less dramatic. In a room with a high noise floor (HVAC running, 4-year-old child being a 4-year-old child, etc), I actually prefer Dynamic Volume enabled (but set to low). It's also nice in the evening after my daughter goes to bed and I have less fear of explosions or car salesmen startling her out of bed.