^^^ Norseman, I believe that you have Dusky Grouse in your area. Another fine example of a bird with loud and repetitive hoots.
I have the Sooty Grouse. Both were called 'Blue Grouse' until 2006 when they were split into 2 groups. The Sooty Grouse has very loud, low frequency hoots. The hoots can be heard over a mile away. In my area, the Sooty Grouse does sets of 5 hoots. It sounds like wood knocking. The repetition is precise and seems mechanical. It gets better. The Sooty Grouse is considered to be ventriloquial. I had one that would follow me. Always above and behind me. Drove me crazy.. One day, it came out the tree tops like an out of gas Hail Mary pass and landed several feet away. Odd for a game bird to land by a human. It walked around for awhile. Interesting diet of pine needles that these Grouse have. Lots of food.