One recent night at 10 p.m., Denver public health investigator Justin LaMascus rolled up at a west side dance club and bar, responding to complaints from next-door apartments alleging drunken debauchery, fighting, and gunplay. Violence wasn’t his focus, though he’s been issued a bullet-proof vest for protection. He stood in a halo of pale security light between the apartments and the bar’s back doors holding a beige box with a protruding sensor measuring sound levels.