Type of actuator, - electric, air, hydraulic, spring return??
speed of actuator?
Manufacturer of actuator?
Model of actuator?
Do the valves close against flow or isolate a stationary flow?
what is an "abnormal sound"?
what is a normal sound?
what are the other actuators - different in any way?
does the sound come from the actuator or the valve?
How do you know?
How old is the equipment,
Have you asked the vendor?
What other investigations have you done?
Any pictures?
Any video / sounds able to be posted or linked to a you tube video?
Try to provide answers to that lot and then we might get somewhere
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.