Knocking in Mason County, Washington

Over the Labor Day weekend 2010 my girlfriend and Newfoundland dog were camping at Lake Cushman, WA at the upper Camp Cushman campsite. We had dinner, an evening walk and then to bed in our seperate tents. I was cuddled up with my dog when all of a sudden a very loud earie whooping call burst through the quiet night, awaking me and the dog. My dog growled and flipped himself over & broke the tent pole. He was very agitated, nervous and couldn't calm down. The whoop sounded longing, lonely or lost in tone. It was definatly a female tone, the whoops went "whooop whooop whoop, whoop whoooop.." then would stop for about 15-20min, then again "whooop whoooop...." on and on for about 2.5 - 3hrs. The noise came from up above the campsite away from the Lake. It sounded really close but could tell it was far away, perhaps about 1- 2 blocks away. It was difficult to tell due to the woods, lake and projection of the very loud voice. I thought it could be an owl but no owl sounds like that, then I thought maybe an Elk but once again I've never heard an elk like this before. I couldn't go to sleep that night due to my dog wouldn't calm down, he was on alert all night until it finally stopped. I was petrified and was up all night wondering if this creature making the noise was coming to visit us in our tents. When I woke up my friend had heard the same noise and wondered if it was an injured dog howling but then when I mentioned sasquatch whoops she had an Ah-hah moment and realized no dog could make this noise. Others campers gathered in the AM discussing the mysterious noise, some said it was a bard owl, spotted owl, a coyote, an elk, but I felt in my bones it was the same noise I had heard from a recording on BFRO site (1974 Ron Morehead Sierra Nevada whoops & knocks) Camp Cushman is most likely being closed due to some lawsuit w/the native americans over land use.