Weird sound – hoping to definitively ID it
On about June 15th, I pulled the innards out of one of our Panasonic bathroom exhaust fans to clean it. It had been a decade or more.
Everything went fine.
Starting about three days later, while sitting in another part of the same level of the house, I heard a “WHOOP” sound. Over the next 20 days, I heard the noise 12 times. On the days I didn’t hear it, it may not have happened. I also may not have been in the house.
The noise always happens between 11:45am and 3:30pm.
My wife reports having heard the same noise on two different occasions … at 10:30pm. I’m not awake at that hour and have to take her word for it.
This (about 7s in) is the noise … in all its glory. I put a digital recorder in the bathroom for the above-referenced daytime period last week and … caught the bastard.
I had to start with the assumption that I did something wrong. Some of you will understand
I pulled the fan guts again, disassembled them, made sure everything was tight and right, checked the operation of the ‘damper’ (in the attic, juxtaposed to the fan’s (permanent) housing), and everything worked as expected.
Three days later, though, we heard the noise again. 1:58pm.
I was assuming that the noise was expansion as the attic (where the fan housing lives) warms up, and that a 10:30pm noise was contraction as the attic cools down. That does line up with our temperature patterns around here.
Another possibility is an animal … something, something. But I’ve neither heard nor seen any evidence whatsoever that we have an animal freeloading in our house.
Are we positive that it’s the fan? No. Are we positive that it’s coming from the powder room? No. Pretty darned sure on both fronts, though.
My early thought was some weird “low battery” notification from … something electronic, but we can’t identify anything electronic in that part of the house.
And why a four-hour window for something electronic?
My brother suggested … take the fan guts back out and leave them out for a few days to see if the noise ceases. But – practically – that takes the powder room out of commission because setting up and tearing down … twice … for the fan R&R is a lot of work … for this sickly guy. So is running up and down the stairs to use the lav, truth be told
When I cleaned out the fan entrails, I also air sealed the junction between the fan box (in the attic) and the drywall bathroom ceiling using metal HVAC tape.
Like so:
My theory (sparked by my wife’s comment that it “sounds like opening a canning jar”) is that the air sealing created some sort of nearly air tight connection between the fan housing and the drywall that – like a jar of spaghetti sauce – breaks suction when you open it. I think it probably ‘breathed’ better until I monkeyed with it, and – as the roof and attic above the fan warm up – expansion “breaks the seal.” Later at night, as the roof and attic cool down, the seal breaks again.
Anybody ever heard this kind of noise in a home before? Anybody buy my theory? Anybody have another possibility for me to consider?
Anybody think an exorcism or forced sale of the house is in order?
I know the next test would be to just get back up on the ladder and break the seal, either by removing one side of HVAC tape or simply cutting a single slice in one piece. But I don’t want to go up on the ladder (9ft ceilings) again any time soon, and … knowing the right answer probably wouldn’t change my strategy – ie, I’d still take air sealing and a weird noise over an air gap and blissful quiet
But if it’s something else … well … that really would be something else
ETA: there’s no correlation between the noise and whether the fan is ON or OFF.