Hello Carl, I would bet my next to last dollar that the sound RFI that you are hearing is a street light starter circuit. I had the exact same sound from one about 1/2 mile from me. In my case it would come on and increase with intensity and suddenly stop. A short time later it would start up again and start the process all over again. It was just a few months ago and it was cold outside and I didn't want to look for it.One night I spotted a lamp trying to start up and thought I'd better call the town electrician but someone beat me to it.
Most of the time its a bad bulb and not the starter. I looked at Google maps and I see one right down the street from you and there are others down by that bay or whatever that area is?
Good luck..
https://www.youtube.com/watch?v=7ZX_eJeQLUc