New fan, high pitch noise

I just replaced the fan in my Airport Extreme today. Once i booted up the router, I'm now getting a high pitched noise. When I start the router, it initially doesn't make any noise. I can see the orange light, etc... But, once it starts "initializing", maybe 5 seconds after start, I get a constant high pitched noise. Since it's a brand new fan, I'm wondering if this is coil whine? If so, I don't understand how a new fan could cause this? Anyone have any ideas as to what's up? Or, maybe the new fan is just noisy? It's a sunon fan that i bought off ebay. Curious if anyone has any thoughts based on these symtpoms?

Doing some more research, I'm reading that sometimes replacement fans do have a high pitched noise. So, it might indeed be the new fan. It looks to be the same brand (Sunon) as the original, so I don't know why there would be noise. Very sad... Past my return period on this fan, too.