I've had my eye on these for awhile, I like the modular design and easy of use and maintanence, but I refuse to buy any fan that doesn't list the dba. Personally, I don't buy any fan that doesn't list the exact specs, especially listing the sone or dba
On page
11 of their extended PDF for the TD series, it says this:
Fan sound levels are measured in sones. At this time there are no sone level test standards available through HVI due to the
fact that remote mounted fan noise levels are in proportion to the following: type of duct, length of duct, fan distance from the
intake source and other miscellaneous factors. However, it is generally accepted that remote mounted venting is usually quieter
than standard (in room) venting.
Thats enough info for me to not buy one.