an important fact is with a roof a terrace keeps/amplifies the sound, when they switched blackburns "Darwen End" fans to the Blackburn End the same number of fans made the same noise, but it was no where near the volume generated at the darwen end, the diference was the darwen end had a much lower roof, so less away fans installed there,sounded much louder.
it aint just the rain that would be n issue.