WD drives are particularly bad about bearing noise in my experience. Usually the drive starts off quiet and deveolpes a majority of its whine within the 1st couple months. After that initial "break in" period the drive slowly gets louder, often gradually enough so that it is not noticible until you replace the drive.
It is also possible for seek noise to increase. I've noticed many of my older Quantum drives and even some reletively recent (120GXP IBM for example) drives started off with quiet seeks which got louder as the drive aged. I believe this identifier also follows the "break in" pattern.
However with the advent of FDB, nearly all my drives are quiet; even years after their purchase. I am happy with the noise qualities from any of my newer drives including Samsung P80, Maxtor DM+9, IBM 180GXP, and Seagate 7200.7 (all P-ATA)