Raven Hill Recording Pt2

2022 04-07 Here is an odd set of audio clips recorded between 1 and 2 a.m. on April 7th 2022 in Trinity County, California. Initially I thought I had something pretty crazy but I think it is a biologist surveying for Spotted Owls.
I'm not sure what the weird whistle recording is. I couldn't find it anywhere related to Spotted Owls. There are also a couple of wood knocks that occur in this capture. The silence in this area is pretty amazing and goes on for hours at times. No frogs, bugs, birds etc. Tree structures are present here as well as rock throwing and other signs of activity.