Ah that's a good idea. It doesn't bother me at all (since I know what it is, it's rather comforting and brings back good memories) but never considered that it might bother people who have no idea what it is (I've heard it as far as 20mi/30km away from a shipping lane in the US.) I live about 1mi/2km from a canal that regularly has barge traffic late at night. I'll see if I can find a mic or equipment that can pick up the hum, then do a little study. It'll be fun and also make it easy to reproduce around the world.

Edit: I've also considered that the frequency could be a resonant frequency in the human body for some people, making it seem unnaturally loud. My wife can't hear it.

> I've heard it as far as 20mi/30km away from a shipping lane in the US

Have you taken a look at The World Hum Map (linked from the article)? There are a lot of data points that are deep inland, way more 30 kms. For example there points in the Australian outback, and all through the "flyover states" in the US.

I did, a lot of cities are near navigable rivers that barges go down. I don't think all hums are boats, but I'd be willing to venture that most near waterways are.

I work in acoustics. Very familiar with data acquisition and processing. Hit me up if you need any processing help.

That would probably end up getting reverted because wikipedia forbids original research