Recently, sometimes, I've been hearing a strange noise coming from the dashboard, from the Ac vents, it looks like a boiling sound, coming from the engine.
I made a little video, but it's not very good. I hope it's enough for any tips:

H2 noise - YouTube

I opened the hood, but my exhaust makes so much noise, that it's very hard to isolate this sound, so I can only distinguish it from inside the h2, with doors and windows closed. I can clearly hear a boiling sound coming from the ac vents.

I checked the temps on the cluster every time I heard this, and everything is good.

If I go to the back of my truck, next to the exhaust pipe, I can hear a similarity of that boiling sound on my exhaust, so maybe it's something within the exhaust, I don't know, I just hope it's not anything engine related..
Any tips on this would be great. Sorry for the bad video, and the audio is low because the boiling sound is not that loud, but noticeable even with the music on.

 

Is you blower motor on?

 

No, it was off...