I hear this all the time. I was just talking to someone about it. It’s not everyday but it’s frequent. I hear it mostly in the morning and at night.

It’s always the same length, about a second. It’ll come in pulses of 2 or 3 usually. Spread out a few minutes a part. It definitely sounds like an electronic sound. Almost like a sci fi satellite sound but deep in the water far away. Or maybe a far away whale mourning or something.

I just traveled for 3 months and heard it spread across 10 cities.

It’s very weird...