Help Desk Enviornment?

Looking for insight regarding what may seem like an odd question. I manage a help desk of 18 people in a fairly large call center. We work here with the lights off, the only ceiling lights that are on are emergency lights which cannot be turned on or off. Those lights consist of less than half of the ceiling lights. People prefer that the lights stay off, it’s quiet, its dark. I am wondering if turning the lights on, if it would increase productivity? It is noticeably louder in here when the lights do come on. Has anyone had this type of experience?
And what were your results?