Tacoma Whine Noise

Problem: have been hearing a faint whining sound, almost like a supercharger whine (no I don't have a supercharger) coming from an inconspicuous place. The noise increases and decreased with RPM increase/decrease. Does not sound like it's coming from rear of truck. I only ever hear it when I'm driving, not sitting still (so maybe wind noise through a weather seal?)

Again it's not very loud. Turned truck on a second ago to try and pinpoint source but was not really hearing anything out of ordinary.

So far I've read it could be idler pulley, transmission whine, sound system, etc.

Troubleshooting:
What are some quick/easy things to rule out? I have aftermarket front speakers but even with stereo off I still hear the noise but I'm no audio guru, would I be hearing alt whine through speakers even when stock stereo is turned off? Or would an amp possibly make the noise?

My next plan is to pull power from amp and see if it's the problem.

I am also going to try and record the sound next time I take a drive also.

 

Check the tweaters in the door buy the lever. When they start going bad they put off a really annoying whine sound even when power is off to the radio

 

Might seem grueling but.. take the 5 minutes.

Release the tension on your belt and just pull it off the tensioner. Leave it in its proper path everywhere else. Shake your idlers around and make sure they don't move. If you're not sure pull one off. How many miles are on it?

Also FWIW... I read a vague article on here about idlers and changed mine in about 10 mins. It's that easy.