Sounds too high-pitched to be coming from deep underground. I would guess there is an architectural flaw/feature in a building or buildings (metal or glass plating perhaps?) that is catching wind at just the right frequency, causing the resonating hum.
Sounds too high-pitched to be coming from deep underground. I would guess there is an architectural flaw/feature in a building or buildings (metal or glass plating perhaps?) that is catching wind at just the right frequency, causing the resonating hum.
I think for this sound, that is a very plausible answer.