Perhaps playing for the Miami Heat for two years has thrown Chris Bosh's perspective off completely. After all, last season every arena in the NBA booed his teammate LeBron James with passion, and the Heat's own home crowd isn't exactly renowned for its rowdiness.
That's the only possible explanation for these comments, as quoted by Ben Golliver of Eye on Basketball:
"Everybody keeps talking about how loud it is," Bosh said. "It's regular. We've been in a lot of other arenas and it's about the same. Once it gets really loud, it's all about the same."
I've never been on the court during crunch time, so my perspective is solely that of a fan whose game experience is primarily in Sacramento. But it does seem as if most arenas hit the magical decibel level (at least as expressed through the TV) where it's just loud. It's like how once it hits about 95 degrees outside, it's just hot. The difference is irrelevant: it's just hot.
Most NBA arenas (even Miami in Game 7 of the East finals!) simply get loud in critical moments. That's probably what Bosh means.