Identifying an Owl in my suburban area in Northeastern PA?

There's been an owl living in different trees around my house for years. I know next to nothing about owls but I'm curious about this one. I've only seen it once and it's of a decently big size, and it's a brownish color but I only saw a glimpse of it. It hoots in the daytime. It does not screech. If I could describe it's hoot, it's very low and slow and I find it very sweet. It usually goes" Hooo....Hooo.....HoooOOO" With a higher-sounding end. I'm in Northeastern Pennsylvania. What kind of owl could this be?