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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!

isherwood
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Darren
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  • Welcome to DIYSE. Be sure to [take the tour](https://diy.stackexchange.com/tour). Would you describe the sound as air rushing or motor humming? – isherwood Mar 05 '19 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 Mar 05 '19 at 15:56
  • Hi isherwood, I would definitely say air rushing. – Darren Mar 05 '19 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. – Platinum Goose Mar 05 '19 at 15:59
  • I can definitely confirm it vents to the outside of my home. I have two vents on the outside of my home, one for the dryer and the other for the exhaust fans. I confirmed this by turning the fan and checking for moving air, the turning the fan off and the air flow stopped. Air flow seemed pretty strong so I don't believe anything is blocking it. – Darren Mar 05 '19 at 16:08
  • You may want to read this post, not exactly your question but a pretty good list of things to check. https://diy.stackexchange.com/questions/70328/how-can-i-quiet-a-bathroom-exhaust-fan-that-became-loud-only-after-the-duct-was – Platinum Goose Mar 05 '19 at 16:15
  • Thanks Platinum Goose. That was a great post. The problem is I can't figure out a way to check most of those things (ie. Length of duct, how many bends...) because the duct run is in the space between the 1st and second floor. I poked my head through the fan opening while I was installing it but you can't see much. – Darren Mar 05 '19 at 16:30
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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. – aparente001 Mar 06 '19 at 03:06

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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

https://www.energyvanguard.com/blog/57709/How-to-Install-Flex-Duct-Properly

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

Criggie
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Joe Fala
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