2010 5.7L Mystery noise from the front end

Hello all, I've been trying to diagnose an odd noise coming from the front end of my vehicle and I was hoping to get some advice from folks who know more than I do.

The symptoms:

• low pitch, chuffing/rubbing noise
• Only occurs above 1500 RPM
• Only occurs while the vehicle is in motion (haven't been able to replicate it in park or neutral in my front drive)
• Frequency (# of rubs per second, not the pitch) of the noise is directly related to RPM
• Does not seem to have any relationship to vehicle velocity or what gear I'm in.
• When I let off the gas and the engine RPM goes down below 1500, the noise goes away.

My thoughts so far:

• Probably not the brakes rubbing since it happens.
• Possibly something on the serpentine belt, though if that were the case I would think I could replicate it in my front drive.
• Possibly transmission (please god no)
• Possibly engine (also please god no)
• Possibly motor mounts.

If anyone has any advice or diagnostic steps I can try out, I'd appreciate it. Haven't been able to find anything online that matches this exact set of circumstances.

 

It is probably the serpentine belt tensioner and/or the idler pulley. Not sure what your miles are but I've had to replace both every 80k miles or so. In general, I replace the belt, tensioner and idler together every time. It's a cheap and easy job to replace the tensioner and idler. If you want to check them then release your belt and spin the pulleys to hear if they make noise. I don't bother because they are each only about $50 so I just replace them every time.