Knocking in Tuolumne County, California

My girlfriend and I were finishing a week long backpack trip south of Sonora pass and we spent our last night on a ridge line seperating two deep canyons. To the east was Kennedy canyon which we had hiked up that day, to the west was another canyon of which I don't know the given name, only that it was very deep and rugged. I was a bit concerned about our campsite due to the lack of decent trees to hang our food in (this was before bear cannisters, and packers still hung their food in trees to keep it away from bears), they were all very small due to our elevation. I awoke about 1 a.m. to the sound of rockfall off one of the peaks above us and I sat awake because I thought it was possibly the sound of a bear coming up the nearby creekbed. Quite suddenly the sound of what I assumed was a large gust of wind came barrelling up the western canyon. This immedietly struck me as odd as the night was very still. The sound started as a low moan, growing in strength and intensity and eventually raised in pitch until it resembled a scream bouncing off the mountain walls. This episode lasted approx. a minute. As best as I can put the sound into print it went something like this: WHOOOOOOOORROOOOUUUUUIIIIIIEEEEEEEE. I have spent a good part of my life knocking about the wilderness and many years as an alpine mountaineer. Now I have sat through many a lonley night on a mountain ledge waiting for first light with nothing to do but listen to the wind howl around the peaks and I've heard it do some pretty strange stuff, but when I heard this noise I was dumbfounded. Now I was wide awake and all was still again. No wind whatsoever. After several minutes the sound began again, building up the canyon until it reached the same screaming crescendo. I thought "whoa, that was bizarre". Satisfied that our food stash wasn't being raided by a bear I tried to go back to sleep when a very similar moan/howl/scream came up from Kennedy canyon to the east. The sound was similar in tone and building pitch but seemed fainter, possibly originating from a more distant point. This is when my girlfriend awoke and I asked her what she thought of the sound, but she wasn't much of a wilderness person and I didn't want to scare her so I didn't push it.