So periodically (every few months, for a few days or a week) I will hear an annoying humming noise at home. It is worst at night, probably because the air is still outside and noise transmits better - and there is less ambient noise. It sometimes rises and falls, sometimes seems to pulse, but it is always exactly the same frequency (about 200 hz). I know it is real and not in my head because I captured it on my phone's spectrum analyzer ap (photo attached -- how cool is that ap?) and it is definitely coming from the window. I'm about 5 miles from the Limerick nuclear power plant, so I'm wondering if I'm hearing a bearing fail on a generator. Normally, this would just be a curiosity, but I think it is contributing to the trouble I've been having sleeping this week. I lie in bed, fixated on the sound. Anyway, mostly just venting, but I wonder if I could build myself an active noise cancellation system or soundproof my window or something.