I cannot stand nosiy items so I was looking for the quietest fan. It''s not as quiet as I had hoped and it was VERY difficult to install per my electrician.

The fan is a great fan, can't believe how quiet it is. Was relatively easy to install, although I needed to ask customer service for some clarification on the instructions. Kaze was able to send me a clearer diagram which made everything very straight-forward. In addition, the humidity sensor seemed dead on arrival so Kaze sent me out a replacement at no cost which was awesome, didn't need to fight at all. Really, really great customer service, I only wish all companies replied so quickly and comprehensively. Thank you!

First thing I did when i got the box was hook it to a test plug and turn it on. I had to check the blades to make sure it was working! Really moves the air, and the motor ramps up to keep the airflow going at 100cfm - adding the reducer or blocking the airflow cause the blades to spin faster. Installed it (super fun refit of a 40 year old NuTone that finally gave up) and asked the wife to hit the switch to check the power and she swore I screwed it up because she couldn't hear it!
Did remove the back flow flapper because our existing duct work has one in place and the slightest air pressure difference causes it to bang around. Probably the only really cheap part in this.
Super pleased with the unit so far, hope this one lasts at least as long as the old one.
Edit: did some db measurements with and without the 6->4" reducer. For 6", the measured in room db is +10db, which equates to 0.3 sones - spot on the advertised rating. Putting on the 4" reducer cranks up the db to +35ba, which is around 1.8 sones. So this is probably what's got other reviewers upset with the noise level - the reducer collar makes the fan speed up to keep the same airflow. Putting this in a wall will force you down to 3" which will only make it worse.

We just had thr bathroom redone and my overly sensitive wife wanted NO fan noise. I purchased it fir that reason. I am about 75% deaf. This thing makes just as much noise as my old small square 50cubic ft fan. However it is a monster when it extracts thr bathroom air.Tons of steam or a horrendous dump won't matter.This fan clears it al in a few minutes AT MOST. That is amazing. If only it lived up to it's low "sones" rating.

I ordered and installed 3 of these fans in our high-rise condo. They are very quiet. They replaced noisy fans that were high volume but had vibration problems not associated with being dirty. These new fans were quite easy to install-but issues related to the old fans made it a big job-for example the existing wiring was too short to reach and electrical work was required. Installation was easy. The flapper in one of the fans was dislodged during shipment and 2 required nylon bushings were found loose in the fan body or packaging material. The fans really do just slide into place once the exhaust connection is made. These fans have a 6" connector so I had to install a reducer on each fan-however I have not had problems related to reduced air flow because the fans were already oversized for our bathrooms.

Here is where things became a problem resulting in extra work and complications: the flapper valves are not well designed and will actually tap against the metal reducer and make an annoying sound. This was caused by the reducer I installed and was easily fixed using a 6" exhaust extender about 8" long installed between the unit snd reducer. Even with this fix, the flappers do NOT close completely and actually allow significant backflow. There is at least 1/4" of space around the outer edges of the backflow flappers when closed. For the 6" outlet, this means that a minimum of about 2.3 sq inches of open area around the flapper valve when it is closed. (Area of a 6" circle is 28.274sq.in. minus area of a circle 5.75" of 25.967sq.in. = 2.3 sq in open area). The fans ARE extraordinarily quiet-in fact it is easy to forget they are on. I have since the original installation replaced the flappers with positive action flappers that close 100% when the fan is off. Even though these issues came up, I would still buy these same fans because of the power, quietness and especially ease of installation (because I had no access from above).