The first time we went out camping this year was back in June. The first night we were there we heard this sound and couldn't quite figure out what it was. We were camped in an open spot in the woods and heard it flying in large circles above our heads. Because it was night, we all assumed that it was a bat catching bugs and we were hearing the sonar it uses to locate its prey.
Well, that was what we thought until we heard it again periodically throughout the day. We saw what could have been a bird flying around overhead. It was a smaller in size and had very short wings. It very well could have been a bat but I don't know of any that fly around during the day. Maybe they do, I don't know.
The recording was done with my cell phone because that was all that I had on hand, I was camping afterall. Make sure that you turn your speakers up on your computer because it's not that loud. What you're listening for is the woo-woo-woo-wooo-woooo that starts quiet, gets lounder, fades a bit then stops.
I would love to get some feedback on this. If you know anyone, like an ornithologist, who would have some more information I would love to get his or her opinion. We were just north of Highway 43 near the BC border when we heard it and it was in early June, if that helps. It was a very loud noise in person and there may have been two of them.