WTF is that wobbling sound under the hood?!

Title says it all. Started about 2 or 3 months ago, I hear it while idling, not sure if it's making that sound while driving because I don't hear it... mechanic buddies thought it was the alternator, but I had that tested and that's fine. But it must be something ::near:: the alternator bc that's what they thought it was... I have an audio clip but not sure how to add it : / So tell me how and I will!

EDIT:

After listening to a bunch of stuff on YouTube, I'm wondering if the sound I'm hearing is an idler pulley dying...

 

Remove the belt and start it up for a few seconds see if the sound goes away ....

 

Our trucks are full of wobbles and noises. As long as it still runs, just leave it.

I’ve tried to figure out and fix all the noises in our trucks and I just gave up on some of them. Some of my wobbles and noises have been going on since I bought the d new with 7 miles on it. I would spend months trying to figure out noises and then would just give up.

As far as the audio, if you upload to YouTube and just post the link, it’ll show the YouTube video on here.

 

Co Mod Day is approaching, and my plan is to just replace it then, and keep my fingers crossed. Good to know that I'm not the only one with some strange noises emanating...

 

It just these trucks.... I'm paranoid to death of noises but this truck is helping me deal with that lol

 

There are plenty of noises I am content to ignore. Especially once I identify where it's coming from. A wobbling noise in the engine bay is something I'm not willing to ignore. Best case scenario, the belt breaks and you discover it's a bad belt or a bearing going bad on a pulley - which you'll identify when the new belt gets eaten, or if the wear pattern on the old belt makes it obvious.

Having local Taco heads around to check it out on a mod day is an amazing resource to have. TW is an awesome community.