I recently installed a new bathroom fan in our master bath in hopes for a much quieter environment. I installed a NuTone Model # AERN110 (110 CFM, 1.0 sone).

I've never had an ultra quiet exhaust fan before so I wasn't sure what to expect but I wasn't impressed, it was still pretty loud. I just figured that was normal until I visited a friend and noticed how quiet his bathroom fan was. His fan was 6 years old and almost double the sone rating of mine.

I decided to reach out to NuTone technical support and after asking me a few questions decided to send out a replacement motor. I just replaced the motor and it sounds exactly the same. I'm assuming this means the problem in on my end but I don't know what to look for.

The fan is installed in the ceiling between the first and second floor (No attic access). It's connected using 4 inch flexible duct pipe directly to the fan (No reducers or elbows). I don't know the length of the duct but I do believe it vents to the outside but I'm not positive. One other detail that may or may not be important is when the fan is running I can hear it (very quietly) in the other bathroom located on the same floor.

Hopefully I've provided enough detail for someone to point me in the right direction but please feel free to ask questions and I'll answer to the best I can. Thanks for reading!

  • Welcome to DIYSE. Be sure to take the tour. Would you describe the sound as air rushing or motor humming?
    – isherwood
    Commented Mar 5, 2019 at 15:55
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    I'd start by finding out where that vent goes and if it's clogged with a bird nest or something.
    – JPhi1618
    Commented Mar 5, 2019 at 15:56
  • Hi isherwood, I would definitely say air rushing.
    – Darren
    Commented Mar 5, 2019 at 15:58
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    I installed a fan and tested it out while it was vented to the attic and it was pretty quiet. I then hooked up the vent to the outside and it got louder. If you can easily disconnect the vent try that and see if it get's quieter. Commented Mar 5, 2019 at 15:59
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    Does it sound like a rattling noise? Or do you think there's some resonance being created (like a flute)? What happens when you attach some of the same type of flexible duct pipe to the fan when you lay it out on your kitchen table? Maybe that would help you eliminate some variables. Commented Mar 6, 2019 at 3:06

1 Answer 1


Unfortunately the quietness is often determined by the air restriction. Yes a poorly made fan can rattle or the motor can hum or buzz but even the best fans with no hum no rattle no buzz can still make noise if the diameter of the outlet pipe is too small.

This is the problem with installersenter image description here


Flex duct for all its Glory is installed incorrectly 90% of the time if you're going to run a flex duct and leave it all floppy you better run a much bigger duct or just run rigid or install the

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