Recently I was driving my new Equinox on the freeway and noticed a loud roaring sound when I was driving at a consistent speed where the engine was at 1800 RPM. I am taking it into the dealer today. But my Son and I decided to try and figure it out ourselves. It appears that the noise cancellation system has an issue. When I put the car into manual shift and drive at 1800 RPM, there is a very loud 180 Hz tone that comes out of both rear speakers. It does not seem to do this at any other RPM. I am not sure how they sample the noise reduction, but I assume there is a microphone somewhere. There may be a phase differential error that is causing this. Hopefully the dealer can figure it out, it is very annoying. It mainly seems to happen with the rear seats folded down.