Whirring noise from hydraulic clutch?

hi guys, i have a 1997 honda civic 1.5 LS vtec. It has a hydraulic clutch which as of today i was aware of a whirring sound when the clutch pedal was not being pushed. When i push the pedal down the noise stops. I'm not sure whether this noise has always been there and i have only just noticed it, It does not affect the way the car drives though...does it sound like a problem?