How to treat a Ceiling with Corrugated Metal Sheet Roof

I have a 8m by 5m Garage with a Corrugated Metal Sheet Roof, Brick Walls. I record voice overs and Radio Jingles. My studio is in a relatively low noise suburb, I have a plan on how to treat the walls but the Ceiling is eluding me. Ceiling has the normal wooden Framing then the Corrugated Roof Sheets 2.4m between the floor and Roof Framing Im confused as to how to treat it. i'm really trying to get enough isolation from rain drops noise when it rains Attached is my Floor Plan.

Hi "tremmsipa". Please read the forum rules for posting (click here). You seem to be missing a couple of things! :) - Stuart -