Interesting article on this subject: Get loud, go deaf? Noise levels in arenas can cause harm
"While the effect of noise exposures over the course of an NBA season is not well-studied, one study at Murray State examined the average and peak noise levels expected in their sold-out midsize NCAA basketball arena. The results from this three-game study showed peak noise level of greater than 130 db in each of the three games."
"This noise level corresponds to a sound somewhere between an ambulance siren and a jet engine taking off. Furthermore, of the 15 fans surveyed, one-third experienced noise levels higher than Occupational Safety and Health Administration criteria for hazardous conditions over an 8-hour average (8-hour average greater than 85 db)."