There is an weird humming like sound coming from just south of us, there is no object visibly, but it sound fades in and out of ear range constantly,
it sounds as if a car horn is going off in the sky. Idunno what to say, its still there. fading from quite to loud.
Interesting post. I have heard of this more than once and do wonder what the source is.
The sound is fading in and out most likely due to being blow around by the wind.
A recording would be nice. We'll keep an ear out for you!