An excellent term to describe Dave is "stealth." Along with Dave's well-known patience, his stealth is among the most important qualities that make him such a great detective. Jack is naturally quieter than Dave, but when Dave puts his detective hat on, he is so quiet you could hear a pin drop. This is sometimes necessary in Dave's investigations, because it is important not to disrupt whatever he is investigating. Much like a good scientist tries to make as little impact as possible on whatever she is observing, Dave also tries not to impact whatever he is investigating. He wouldn't want to make any false conclusions.