I can not think of any other way to lower the fan RPM. 7200 RPM should be normal for that processor.
I have a Dell PowerEdge R720 with 192GB ram and a two 2.6GHz 8 core processors in it.  Just the other day I upgraded the two CPUs with 2 10 core 3.0Ghz CPUs. (E5-2690 v2).  All is working just fine with the server except the fan speeds are running over 12K RPMs now and the server is very loud.  Does anyone have any idea what I can do to lower the fan speed I do not want to go back to the old CPUs if I don't have two? Thanks Steven
High fan RPMs after CPU upgrade