High pitched noise from left side of RMBP underneath the keyboard
I bought a RMBP (13' early 2015) recently and found annoying high pitched noise comes from left side of it underneath the keyboard. So I returned it for refund and bought an exactly same one(configured to i7, 16RAM) but the same problem happened again. I can hear it clearly in quite place. Just want to know is it a normal problem for the new RMBP 13 because two machines have the same problem.
MacBook Pro (Retina, 13-inch,Early 2015), OS X Yosemite (10.10.3), configured to 16GB ram and i7 CPU