Sounds almost like a bad pulley to me, but I only hear the noise when the car is moving. Its relatively quiet, but becomes a lot more noticeable when the engine hits 2000 RPM. Obviously something spinning fast and sound seems co-dependent on engine RPM. However when I put it in park, rev the engine to over 2000 and I hear nothing. Bad CV joint or wheel bearing? I don't hear anything when turning, and its barely audible when cruising steadily.. just when I accelerate. I did notice some grease leaking out of the driver's side CV boot recently, but not a ton. Could that joint be going bad?
I have yet to take off the belts and spin the pulleys by hand. I have a stethoscope I can use, but if the noise isn't there when the car is being revved at idle can I rule it out being a pulley?