While a Barred Owl fits the bill in terms of behavior, the vocalizaiton is interesting. A one note call with a fillip at the end for a Barred (or Spotted) Owl sounds like the whistle call that the females do (rarely the male), but is generally high-pitched. The juvenile begging call is also one note with a fillip at the end, but "airy" or "raspy."

>From the description, it seems like the fillip is higher in pitch than the rest of the call. But if the fillip is lower in pitch than the long "hoooo" it could be the Barred Owl one-note call that both adults do.

Like Pete said, Barred Owls have a lot of variety in their vocalizations. You can check my web site with mostly Barred Owl calls and see if something is similar to what you are hearing. I think I have more variety of categorized calls than Cornell or DNR.

http://home.centurytel.net/bobowlcalls/Barred_Owl_calls.htm

Bob Pearson
Packwood


What owl would swoop from behind, absolutely noiseless, and apply quickly,
but not grasp, talons on the side of the head of human walkers?. The owl
does a sharp turn and comes back for a second close fly by. These "laying on
of talons" occurred along a wide grass pathway through alder and good sized
firs. Artificial light falls on the path from nearby outbuildings. The
encounters occur most often immediately after dark. After listening to
Cornell's bird tapes and DNR guide with owl sounds on the web, I cannot
match what we all heard nite after nite to the notes or screeches on the
tapes. This owl emits one "hoo," not a succession of sounds nor is there a
pattern to it. The sound is one long low ooooooooooo with a fillip at the
end--sometimes up as if a question and sometimes just insistent. Sometime
one hoo and not another. Sometime hoo and then another but not close nor in
a pattern. On the tapes, I listened to Great Grey, Barn, Barred, Great
Horn,Spotted owls. Who has one long note?



I saw the owl take a turn in the dusk light after bonking me. Big wing span,
three plus foot wing span, grey on grey. But it was dark. Usually when hit,
the person hit does not see the approach and is in crouch mode so doesn't
see the bird at all on his return.