Susan:--The high pitched squealing or whistle is probably due to the gas traveling through a corrugated flex gas connector. This is the line that carries the fuel gas from the hard piping to the main control valve. The best way to cure this is to go to a larger diameter flex line or install a piece of armaflex insulation over the one you have now. Lots of luck....Bud
I don't know if this is applicable to plumbing, but everytime my furnace kicks on there is a whistling noise. It is getting extremely annoying. I wanted advice before I call someone. Plumber or heating/cooling? Thanks!