Sonata I45 (YF - 2011+) :: Unusual Engine Noise / Loud Growl

I purchased a 2011 Sonata about 6 weeks ago. I like almost everything about it, but the engine is very noisy. I'm not talking about a loud growl when you accelerate, but it's almost sounds like there are 2 frequencies sounding at once. It's higher pitched and at times sounds like pinging or clattering. It's very hard to explain. Unfortunately, sometimes it's worse than others and when I've taken it to the dealer, it's not at it's worst. The dealer I purchased it from told me that it was normal, even though I drove another 2011 on their lot that did not have the sound. Another dealer told me that it was a loud fuel pump because of the high pressure of the injectors and that Hyundai is aware and is working on a new "cover" that should muffle the sound. When I contacted Hyundai directly, they did not know of any new "cover" being developed . Assuming I've described it well enough to know... The only thing I know to do is wait for it to get consistently worse, and take it in again.