Report 47014: Hikers hear "weird vocal exchange" from unknowns near Lake Ann

My son and I were hiking near Lake Ann in the Northern Cascades around 6:00 pm on Sat. Sep. 6, 2014. We were in a little cirque just down the trail from Lake Ann. From the bluff high above us (to our northwest) to a crag on the other side of the highway (to our east), there was a weird vocal exchange going on for 5-10 minutes. It weren't no bird. It wasn't a wolf howl... I'm trying to recall. It was rather high pitched, but it also varied... there were a variety of sounds. Two bear had been sighted up the trail at Lake Ann itself, but we didn't see them. We ran into two other hikers just after the exchange. They had also heard it and thought it strange. I just don't think it could have been human. For one thing, the points from which the exchange took place were so inaccessible, not good campsites. It was starting to rain. Night was falling soon. Humans would have camped together or used cell phones. And the sounds were eerie. Pranksters don't need to go to such remote places for an audience of so few. The sounds weren't like someone trying to spook us or joke. They were eerie.