The .5 - 1 db average sensitivity is for sound in narrow frequency spectrum . Across broader frequency spectrums, the ear is more sensitive. Toole & Olive put the max sensitivity at .25db . Also, these studies were done with ordinary people. My guess is that sound engineers, who have better trained ears (hopefully), should be more discerning than the general population.
Anyway, thanks bigwillz24 for the hold shift recommendation. It does make it easier to adjust things with volumes not jumping around so much at the slight move of a mouse.