Whining noise all of the time

There’s a whining noise coming from my car whether it’s in gear or not. It
increases in frequency and amplitude as the RPM’s increase. I’ve replaced
the alternator with no change. It sounds like it’s coming from a pulley on the
belt but I don’t want to rip into anything else without some clues as to what it
might be. Any help is appreciated.

05 mitsubishi outlander
2.4 l, 4 cyl engine
Manual transmission

Here’s a link to the video of the noise:

Power steering fluid full?

It was low, but I filled it to just below max and it still makes the same noise.

Ok, so I put the power steering fluid in with no change. I listened to all of the pulleys with belt off. There was only one pulley that sounded bad. It’s not connect to any component though, It’s just bolted to the engine block. What is this pulley called. Also, it should be noted that I started the engine with the belt off for a few seconds and the sound went away.

Idler pulley. Good diagnostic work - running engine briefly with belt off.

The bearing in the idler pulley may be replaceable by pressing in a new one - or just buy a new pulley.