I do not think it is surprising at all that the aeroplane sounds louder if it flies lower over your house. We do double derate takeoffs and the first time I used it I was asked by the tower if we had had an engine failure we were so much lower over the end of the runway.
Some airlines combine this with selecting full climb thrust (increasing noise) at 1000 feet. Double derate combined with improved climb on a long runway makes a huge difference to how high (read much lower) you are crossing the airfield boundary.
My local airport is having major trouble with opposition to them building a new runway.....I think there might just be some connection to the current approach to noise abatement.