Just had a new Rheem Classic 90 plus furnace installed.. I noticed that the blower seems to make a high pitch noise that emulates through the ducts.Not as bad in the bedrooms upstairs.I pointed the noise out to my contractor and he seems to think its coming from something the ducts.. I read on another website that someone had the same problem and some wrote this is normal with the high efficiency models to push air.. Any ideas to minimize the noise?Is this normal.. I can live with it but it's a little annoying.. Thx