Most bathroom fans are noisy, badly installed, under powered and inefficient. For bathrooms under 100 square feet, they should exhaust one cubic foot per minute for each square foot of floor space. For bigger bathrooms, the fan should be able to exhaust 50 cubic feet per minute per fixture and double that for whirlpools. Check the box.
But good power is not enough. The exhaust line has to be properly installed with minimum of turns, good connections and a proper hood covering the outside end. Stick your head in the attic and take a quick look. It will be obvious if the installation was done well.
And that noise thing? Buy an inline fan designed to be installed in the attic or check to see if the fan has an HVI rating. If not, it’s because someone doesn’t want you to know how noisy it is.