I have heard this type of sound before.
In MY case...
Once was loose hardware on power wires moving in the wind, another was from
a defective mercury vapor lamp in a neighbors yard near my friends house and
most recently, although not identical, from a defective power supply in an
LED street lamp, although those produce a much broader white noise hash in
addition to the sound you've recorded.
Can you narrow it down by time, day or night? This could be a clue. It's
very audible in your recording, do you have portable equipment to locate it?
I'm leaning toward loose hardware on a power pole.
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