2003 renault megane 1.6 petrol 5 door hatchback noise?

My 2003 renault megane 1.6 petrol 5 door hatchback inthe past 3 weeks has developed a strange whining type noise that increases and decreases with the speed of the car.It occurs in all gears but the perfomance/reliability of the car is unaffected.All fluid levels are fine and no leaks of any kind have been found.Any ideas ?