I drove my Blazer last night and this morning (both cold starts) and when I turned it over, there was a very loud - almost sounding like a lawn mower - sound coming from my Blazer. It's in/around the front of the vehicle and it went away after some driving (~ 5 minutes).

It's hard to hear over the engine running, but it's there - in all its lawnmower glory.

I recorded the noise this morning on my drive to work:

I read it could be the heat shield (or worse). Any ideas? I'm afraid it'll be something expensive.

 

I went out a few minutes ago and got this video - you car hear the noise much better on this one vs. the previous video. Any help would be appreciated!

 

I am having trouble hearing a noise from the youtube vid. I am also confused when you say you hear a lawn mower sound. I think of a loud exhaust sound. Can you use a different description to describe the sound you are hearing.
You need to get the Blazer on a lift and when it is cold, have some one start it and have someone else with heat resistant gloves under the vehicle who can touch the 1./ Heat shields and 2./ Exhaust components and see if they can make the noise stop. Both 1 and 2 can cause a sound from vibration which can go away once warmed up.
A bad fan clutch will cause a loud roaring noise, but usually does it when the engine is thoroughly warmed up.

 

It was the power steering pump failing! Replacing it this weekend. I was amazed (shocked and amazed) that Jiffy Lube of all places diagnosed it correctly. I had an honest dude give me the diagnosis - they could have sold me a bunch of crap, but he said the pump was leaking / failing and gave me a couple of shops to go to in the area!