It sounded like someone snoring with a whistling hissing snore, rather loudly. Finally I got up and slowly tried to locate the source. It was around my house, in the front. Was it from the streetlight? A moment of horror of some imminant and terrible electrical explosion.... No there was something large and feathery sitting on the wires by the street light. An owl! I quietly and rapidly went and got my camera, came out and photographed the owl,

Then I heard an answering whistle hiss behind me. Another one closer up on a tree branch!

They were Barred Owls. A deep woodlands species. I live in a little enlave in a large natural wooded park. I had heard them hoot before (described as "Who Cooks For You? Who Cooks for You Now Ahhh!") but never heard of this noise, perhaps they were hissing at each other like angry cats, or perhaps they were saying harsh endearments.