There are many variables when it comes to range hood installations and noise. What size duct was used for the hood installation? Was it a smooth or ribbed duct? How many bends are in the hood run before you make it to the outside? The answers to this may be aid in understanding where the noise may be coming from in your hood. No hood is noise free though so that is not a realistic goal but proper installation will mitigate some of the noise.

Good luck!

we have 6" round ribbed duct with one elbow and it's coming right outside (it's mounted on the wall that has an opening to outside)
In our previous house we had Broan and we only found it loud in a Boost mode (at 430cfm it was 8 sones). This one is loud on the lowest setting:(

I don't think the hood installation should use the ribbed duct. It should use a smooth duct only. Is it a 90degree or 45degree elbow? I don't know much about these hoods but you can do a search on the appliance forum as I know that several members have bought them in the past.

Good luck!

I'll try to post this in the Appliance forum. I did search and found one post that sounded like my problem, but hasn't been fixed.
Thanks a lot for you help