[PIF]

And does not sound anything like the over amplified noise on those various recordings - at least to me. Perhaps the people making the recording have never heard the hum themselves and are just recording when someone else say to record. Don’t know. Speculation.

If you have ever heard a diesel engine running - albeit a bit rough - and listened closely for a few minutes - you can hear each cylinder firing, in this case there are occasional momentary lapses in the firing causing a rough sound before it resumes normal even firing.

Here (one of those dots on the WI map), the sound seems loudest when lying down and goes away when rising from bed. But just now, over or under I should say the noise of several hard drives spinning I can hear a low faint hum if I concentrate.

[Steve Van Doorn]

It does to me. The first video I gave it had a LOT of static that was filtered out on the second one. The tone is a a little different which I think the filtering changed it or the sounds could be a little different in different locations around the world. I doubt it was a "faked" sound but who knows.

said, "If you have ever heard a diesel engine running - albeit a bit rough - and listened closely for a few minutes - you can hear each cylinder firing, in this case there are occasional momentary lapses in the firing causing a rough sound before it resumes normal even firing"

Here is a diesel truck idling. I raised the speed and slowdown the video's on both. It sounds similar but I don't hear the pistons in the "hum" videos.
https://www.youtube.com/watch?v=j1GMIHV17qo

You do hear the sound. It would be very interesting to hear one day.

[Steve Van Doorn]

One other thing. The crust of the earth is very thin relative to the size of the earth. Is it possible we're hearing the mantel move?

For example the dark blue areas (mantel moving down) and dark red (mantel moving up) we could be hearing those movements.