Recently, the engine has developed a whining.

Recently, the engine has developed a whining sound that increases in pitch and loudness as the engine increases in revs. This occurs whether the clutch is depressed or not, and whether the car is in gear or not. The sound wasn't too loud to begin with, but after driving over 600km on holiday, the noise has gotten a little louder and also sounds a little more rough. I have been told that the thrust bearing could be the problem, and the car had it's clutch replaced 2 years ago due to failure in the thrust bearing. Any help with the cause and solution to this problem would be greatly appreciated!