T320 fan running louder than normal?

I recently moved my Dell t320.  It's in the same room, and it's getting good air flow.  The air coming out is cool.  Nothing crazy is going on.  I can't recall exactly, but I think it's louder than when I was running it previously.  

I don't have a decibel meter, so I can't say exactly how loud the fan is.   I went into the setup settings and idrac settings, and the fan speed is set to auto.  It's not as loud as it first powers on.  It does come down.  

I'm just wondering if a setting changed since I unplugged it.  Or there's not good air flow since I did open it up, removed the large plastic piece inside to get out some dust, then put that back in, but no major disassembly or cleaning.