Product review (1 stars): Poor Quality / Design and very expensive to fix
The unit is 4 years old. From the day one, the fan is not quiet (for $900, it should better be). A year after, started little rattling sound. For the past 8-9 months, it sounds like a diesel engine (I believe the new sound is from the motor it-self).

1) The blower assembly is poorly designed (rather over engineered with poor quality). The fan (Broan Technician calls it as wheel) rotates in a tight space (they better be using Aircraft quality materials). With the heat from the stove, plastic wheel, rubber washers/screws, any small shift, will make the wheel rub against many things around it, making noise. When I opened the unit, I saw the issue. The Broan technician agreed that it is a sophisticated design and no room for error.
2) The motor is not balanced. Making the wheel wobble. That is sending the vibrations to the entire wall (this was happening from the day one).
3) As I said above, the plastic wheel is a cheap part, for a high-tech design / an expensive unit.
4) The motor started making noise in about 3 years.

I would imagine the same story with other high-end Broan Kitchen Hoods,

Now the sad part is, it costs $400 to replace the Blower Assembly - SV08097 (it is the outer shell for the motor + wheel + motor). They don't sell individual parts. Just ordered one and not sure how long the new one is going to last. This might be an annuity business for Broan. If it breaks, I will replace the entire hood with another manufacturer product.

I would not recommend but, before you buy any Broan Kitchen Hood, check the cost of replacing the motor. The warranty is only one year.