metallic growling sound when engine turns on and when accelerating

Hi there! I have a 2012 prius with 102k miles.

The past week I have noticed a metallic growling sound when the engine kicks on, and also randomly when my foot is on the gas. It doesn't seem to change depending on the speed I'm going, and it isn't consistent.

I read through a few threads about the rattling sound issue, but I don't think that is it. The sound also does not go away after starting it up. I'm taking it into a mechanic tomorrow, but... any ideas? I attached two sound files, you can hear it in the background, but they aren't great quality.

Thanks for the help.

 

UPDATE: turns out it was a rusty heat shield.