I am hearing a strange noise coming from the front of my engine. It only seems to happen if I have been driving for a while. I have around 100k miles on my car. Here is a clip of the noise:

https://www.youtube.com/watch?v=_aTX...ature=youtu.be

Here is another video with my hood open. The engine isn't making the noise from before but it doesn't sound quite right:


Any advice on what this could be?

 

I'm no expert and no mechanic but I've had my fair share of experience with the v8 (came from a 2002 a6 with the 4.2).
The first video you linked sounds like a knock sound. The 2nd video sounds just like normal lifter sounds. The ticking is something I heard for many years on my a6 - unfortunately something I never figured out and I've heard on my Audi's with a v8.

I would read through this and see if anything fits/helps:
B6 S4 Engine Knock @ 99K HELP!!!!