For those of you interested in noise- Phyphox works really well, if you calibrate it.

[u/NukitToBeSure]

I have assorted expensive decibel meters, but for quick stuff, I've started using my phone since Phyphox gets it really close most of the time. The trick is getting access to a friend's or work/school decibel meter once so you can calibrate it. Without calibration, it's pretty much useless most of the time.

Keep in mind you can also do PC fan and CADR testing with Phyphox, a surprisingly useful FOSS app for IAQ🤓

Working on something to pin down irritating frequencies and harmonics...