Christine and I were on Incinerator Ridge for about an hour and a half. And almost the entire time we could hear two Ravens squawking. At one point one of the Ravens was creating sounds neither of us have heard before. One of the calls was very low in pitch so I couldn't hear it at all. Another was a knock-knock-knock that at first I thought was a woodpecker. Christine thinks that it was a young Raven who couldn't find or hear his (her) parents because it seemed distressed. We watched the young bird as it made several different calls. Eventually the mother came around and the two flew off together.
After during a little research on the subject, fifteen to 30 categories of vocalization have been recorded for this species, most of which are used for social interaction. Calls recorded include alarm calls, chase calls, and flight calls. The species has a distinctive, deep, resonant prruk-prruk-prruk call, which to experienced listeners is unlike that of any other corvid. Its very wide and complex vocabulary includes a high, knocking toc-toc-toc, a dry, grating kraa, a low guttural rattle and some calls of an almost musical nature. So I guess what we heard was normal -- even though some of those calls we had never heard before.
Here is a photo of that young Raven:
