There's a Persistent Hum in Windsor, Ontario, and No One Knows Why

I live about five miles from Heathrow airport. Occasionally I will have planes taking off over our house which is fairly loud and sometimes I can hear them powering up and taking off - that's quiet and distant and I can't always hear it.

When the Icelandic volcano closed the airspace a few years ago I was stuck by how quiet it was outside. Not just the lack of identifiable take-off noises but I became aware there had been an imperceptible continuous rumble. This came back when the airspace opened.

There are always aircraft in the skies, I presume this low level noise is the culmination of many distant jet engines.

Our living room had a window facing the street, and sometimes one could hear a low pitch humming noise that made that window shake. The first time it happened I remember wondering who would leave a delivery truck in neutral for so long.

It was really annoying, especially because when I opened the window, there wasn't a car parked outside - everything was silent. Until you listened carefully, only to confirm the hum was still there, seemingly at a distance.

So the window was reverberating to the hum. But where did it come from? Across the street there is a military academy, so I guessed the obvious guess: military experiments, of course!

The problem with that guess was that under closer inspection, the noise didn't really seem to come from that direction. Usually, one could only hear it in the afternoon, but the hum was present all week round - and around there only the military worked weekends. But it just looked it came from in between some trees far away. So I guessed differently: a big air conditioning system, some large boat, a generator in some construction yard, a concrete mixer...

The hum's amplitude would slightly vary, and the window would just hum along or even rattle annoyingly sometimes. So I guessed that if wind was a factor in modulating the hum's intensity, it would be relatively far away. Either that or it was coming from a moving source.

One day the hum simply stopped. I never found out was was behind it.

I was on Belle Isle last year, two times, which is a few hundred meters from Windsor, and the sound was extremely soothing for whatever reason.. I spent days on end thinking and reaearching. I finally attributed the sound to some sort of tunnel boring machinery. There are a handful of salt mines in windsor, which i discovered after seeing more than the two tunnels I was aware of, between Detroit and Windsor, in the river, on Google Earth.

I am in the habit of identifying every sound that I am exposed to consistently, which I noticed when I bought a new house. After moving I diligently inspected my HVAC system, computer fans, appliances, which neighbors parked where, and how hard they slammed their doors, etc. Not only do I identify every sound, but I also actively recognize and consider every combination of sounds.(neighbor1.carDoorSlam sounds different when my furnace is on, or furnace+fridge compressor, for example.) Once I know for certain what a sound is, I can identify it immediately, and continue with my current activity knowing that it was just some irrelevant, petty routine happening.

I can't imagine enduring a sound like that for long, while knowing I am unable to identify it; I was able to convince myself that it was due to tunnel boring; but I seldom am reminded of the sound and never disturbed by it, since I don't live in the area..