My house was built in the 70’s. The original furnace lasted until about 2000. As soon as it started running, we noticed it was louder than the old one. Just a white noise from the airflow. It’s loud enough to be conscious of the sound, whereas the other one was more of a background noise. It can be significant when you’re listening to quiet music or something at night.
Is there a reason for this? Is it a characteristic of newer systems, or cheap ones? I looked for info and I think I read something about newer ones being noisy for the sake of efficiency or something, but I might be wrong. Has anyone else noticed this? I think it affects the quality of life to a small degree.
The white noise from airflow is a strong function of the velocity of the air. I think it starts being noticeable around 700 feet per minute. If your new system moves more air, or even if it was designed to move the same amount of air but your old system was clogged with dirt or leaky or dented shut someplace, that would give you more white noise.
I think your living experience would more reflect the air velocities around the outlet grills and the duct leading to them than the other components further back in the duct, but I’m not sure.
If you are getting white noise from further back in the ducts, you can replace some of the close sections with multilayer insulated duct. This is soft and flexible and does a poor job of conveying sound along its length.
It is cheaper for them to make smaller ducts and smaller fans with higher speed motors. This makes your energy cost higher to move the air, and creates more objectional noise. I’ve daydreamed about building a house from scratch with extra large ductwork and large, low speed fans, to make the HVAC system inaudible. But nobody seems to do it that way. The cheap bastids.