A few options. Replace the fan(not exactly expensive). Remove the noise
maker..Fan in front will probably do the job, and Seagate drives usually run
a little cooler than most. You can throw a low-noise fan in there. Or, check
and make sure the offending fan isn't plugged up with dust, and dirt. I save
old toothbrushes for this purpose, and they are great for getting "into" fans.
Clean both sides of the fan blade, as well as the motor body, and inside
the fan casement. Compressed air can also work well for this, but isn't
free. GL
Actually, with 2 HDD's stacked, it's probably best to ensure adequate
circulation with a dedicated fan.