If you are sure that the noises are really coming from the HD then you have limited time before it fails altogether.
If the noise is coming from the HD this is totally bad news. The HD is a precise piece of kit with minute tolerances, and spends its life spinning at high speed. Such devices shouldn't really make any noise at all (except perhaps a tiny high pitched whirr or whine). If this becomes loud then something is running a dry bearing, or grating internally. There is nothing external that moves so cannot be a casual embarce from a cable or fan