My office is less than a mile west of the approach to rwy 1 at ALB, and when walking out of the building for lunch I heard a jet turbine sound like I haven't heard in quite a while. Sounded like a small turbojet, so I was expecting to see maybe an L-39 or something similar size or smaller. Turns out it was a PC-12 on a 2 1/2 mile final.

I thought it was a little weird that I didn't hear any prop noise, all I was hearing was the turbine exhaust. Can't remember having that experience before, and we regularly see turboprops coming in here.

Maybe it was just right at zero thrust or something..

I get a really weird compression of sound as airliners cross overhead my house on a wide downwind for KPHX. Its like zero noise at all... then a descending crescendo waterfall of sound just drops and thereafter sound is normal. Always sounded kinda odd.

Maybe it had the bent tips and it was low RPM?

Could be a MT 5 blade prop. They reduce noise over the OEM Hartzell. Neither makes much noise when not under a lot of torque. They are only turning at 1700rpm.

PC12s sound more like a jet to me when passing overhead than a piston plane.