Metallic rattle in engine area

https://clyp.it/rjg5drcy

Here's a clip of the audio. It starts around 10 seconds in

Within the last few months my trucks been making said noise when driving around town when I let my foot off the accelerator, and now it's doing it even while the accelerator is pushed down. This only happens when the truck is driving and in gear. I can't replicate it when idling at a stop.

I've read tons of other threads trying to pin point the issue, but I'm not finding much. The only thing I haven't checked is the heat shields around the cat, because the noise is coming from the front of the truck.

It doesn't seem to effect the trucks driving ability.

 

My heat shield sounded like a bunch of mad hornets not like that, but if yours is real loose?

 

Just wanted to update this.

I tracked the rattle down to my timing chain. The guide probably broke. Should be getting it fixed this week