That was one of my concerns but wasn't sure.  On the formerly named "California Screamin" and "Rip Ride Rockit", the audio is quite clear.  On Hulk, I can't hear it at all.  It's a B&M with that traditional roar and I can't even hear myself yell.  Plus, the slowdown sections could easily be augmented with speakers surrounding the coaster to create a deeper immersion.