Not a sound, but...
In the summer there are often kestrels on the wires on the worst, most dangerous part of my ride. I can't look at them much as it's a 2 lane 50 mph busy road with no shoulder, but they are heart warming none-the-less.
In the winter when it's dark on the same stretch of road, bats often buzz my lights and I really enjoy that. I don’t see the bats in my car and I’ve never seen them buzz a car when riding my bike, not sure what’s special about the bike to them.