Dockjock,
A T-tail should free up a little space up the back since there's no need to put a tailplane mainspar through the cabin.
As to noise, I think the use of a T-tail in itself won't make much difference - maybe a little because the fin will act to insulate any tail noise from the fuselage - but frankly trivial. More significantly, T-tails often go with rear engines, which are significantly quieter in the cabin (compare, say, cabin noise in a VC-10 and 707).
G