Is there a way to find out if a sound is real or imagined?

A few months ago, I started hearing this low humming~buzzing noise and I can't tell where it's coming from or if it's even real.

At first I thought it was something electrical in my house (I only hear it in and around my house) so I checked all my appliances and turned everything off and it turns out wasn't coming from anything I had plugged in.

I hear it loudest in my bedroom and outside in my yard. Inside, it sounds like it's coming from something in my house and outside it sounds like it's coming from something outside. When I try to pin down the source it's like trying to find the end of a rainbow!

I have asked other people if they can hear it but so far no one has been able to positively confirm or deny it.

I can't record it because it's too low of a sound to be picked up by any recording device I own.

I'm at a loss here and this noise is starting to drive me crazy. What can I do to find out where it's coming from?

Any ideas or relatable experiences will be greatly appreciated!