Is this noise normal?
 

Below is a youtube vid I found, with the poster saying he wasn't sure what was causing the noise. However, I noticed two different noises in the video: One distinct rhythmic knocking in the beginning that is proportional to the speed, and a different noise right before the end after he releases the clutch and gets on the gas (sounds like a tractor to me).
[media]http://www.youtube.com/watch?v=PMpUKWb5zz4[/media]
http://www.youtube.com/watch?v=PMpUKWb5zz4

My question is, is the second noise that's near the end a normal noise for S2000's? I've noticed that noise in mine (however a little quieter), and my mechanic swears that it's a normal noise for S2000s. Just weirds me out because it definitely doesn't sound healthy to me, but I'm not familiar with these cars yet and my mechanic is apparently very familiar with S2000s (Source1 Automotive in the Cincinnati area). Anyone else familiar with this noise? Thanks.

That noise is blown differential 99%, 1 % something else broke near rear end

This is frustrating because I've had other people absolutely positive it was a throwout bearing. I'm just hoping whatever it is won't break the bank to fix it. I'm assuming you've experienced this noise or problem before? Do you know how much it cost to fix?

Bump. Could anyone else chime in on this? This seems like it would be relatively common.