Had 3 30yr old Carrier furnaces. The heat exchanger cracked on two of them and I got suckered in to replacing them with new Lennox high efficiency furnaces rather than try to repair.
Now when the furnaces turn on there's an irritating low pitched whine coming from all of their fans that you can hear all over the house. The installation company has been back several times and tried doing a few things like lowering the fan speeds, but on the 3rd call gave up and said it's normal because today's units use much bigger fans so you're going to hear them running and to just live with it.
Such bullshit that a 30yr old furnace is basically quiet when running and new ones are noisy pieces of shit - are there any brands that are whisper quiet when running, or upgraded fans or something to make it quiet? I'd happily pay to rip these POS out and put new units in if I could find a quiet one (but I don't think you can go to the store and ask for furnance demos of various brands???)