In the story Hoot Officer Delinko tells the supervisor the truth about the owls is because he doesn't want them to die.
IN THE BOOK HOOT
Curly is a construction builder
The owls's sound is a hoot.
Hoot hoot hoot
you get hoot hoot at night in the marsh game
Ash's hoot hoot evolves at episode 183
hoot-hoot evolves at level 20 into noctowl which will not evolve no further
The heh sound that officer Delinko heard was likely the sound of an owl hooting in the distance. Owls are known for making distinct hooting sounds, especially at night.
A hoot sound
Hoot was published in 2002.
I am pretty sure hoot hoot is near one of the entrances to mount coronet. You can use the pokedex to find out