Having spent the coldest summer in my life in a top-floor apartment in NE Brussels, I can say with authority that the MD-11 is really loud. From the ground, 744s sound like clipper ships in comparison.
That said, I have little sympathy for the NIMBY crowd in two conditions:
A) Their domicile was constructed after the airport was.
B) The government was so stupid/corrupt/bureaucratically dysfunctional as to construct an airport immediately downwind of their capital and major population center.
B) applies in this case. It's now worse that the EU has moved all their bureaucratic machinery to northern Brussels.
Trains go slowly through Brussels., but there's only so much you can back off the throttle in climbout.