My wife is an avid birder. She and a friend were volunteers in a barred owk survey here for several weeks. I went along to help. The survey was done at night. They played a recording of barred owl calls in each of several carefully documented sites, wait for a measured time, play again, note if we got a reply. Totally cool when we did. The owl would hoot and then come closer and hoot again. We could hear rhem call a long way off, making their way to us.
Another thing they have done was to use a call tape that had several seconds of calls by each species of owl, arranged in ascending size, (from pygmy to great horned, I think).Apparently an owl will respond to a call of any owl of its own species or to a smaller species, it will go silent if a bigger owl is calling. Using this tape, they would work a responding owl with ever larger owl calls until it quit calling back, which along with recognizing the call it was making, helped identify the owl you were hearing.
I thought that was a pretty cool thing to do in an evening....