2008 Toyota Prius - Strange Noise

We’re on a family road trip. What just started happening yesterday was, as the mighty Prius powered us up a hill, at maximum exertion it would make this rhyrhmic whooshing noise. Seems to be coming from the driver’s side of the engine compartment. It’s not in the wheels or suspension because it happened anywhere between 52-77 MPH. i could make the sound go away by backing off either the cruise control or the pedal a little.

And your question would be? What is this noise? Is it safe to drive? Where is the nearest Dairy Queen?