Flute sound from engine

I have a 2014, Tacoma Access cab, 4-cyl with auto. which I have been totally enjoying. I noticed after Iowa turned very cold, ( temps in teens )that , at times, when I accelerate I hear a flute-like tone from under the hood. I'm sure all is well, but I wonder if anyone else has experienced this. It isn't constant, but seems to be a combination of cold air and certain acceleration demands.

 

Mine does it too. I think it's a vortex in the throttle body created by certain positions of the throttle blade. Kinda like blowing across the opening of an empty bottle.