I have no idea where in the world you live and what your climate is like, but here in Southern California the auxiliary cooling fans in my 1984 XJ6 Vanden Plas doesn’t come on very often. It will primarily come on during the hottest of days when driving up a long hill with the air conditioning running. The coolant temperature needs to reach about 105C or so before it will normally come on.
I suppose that an electrical problem with wiring or a relay could result with the auxiliary cooling fan coming on when it normally shouldn’t, and if you have leaves and other debris around it that could result in a noise like you are experiencing.
A thorough inspection of that area and cleaning out of the leaves is certainly a good thing to do regardless.