CRJ700 First Officer reports that display fans are becoming increasingly noisy making communications difficult. As long as the fans are functional maintenance will not take action to replace them or clean the filters.

Narrative

I checked with the recirculating AC fan off to ensure that it was in fact the display fan that I was hearing to be louder than typical. It was as I suspected; the display fan. It is such that even a phone call is increasingly difficult to make; not to mention carry-on a conversation; or more importantly a check list; etc. It is becoming harder to hear on the intercom; etc. I feel that any time the display fan would be written up would just be 'ops check good' by Maintenance since the fan technically does function. Something really needs to be done about these display fans because they are becoming a safety issue if you can't hear anything at all or muffled to an irritating extent. Among other things; we are pretty certain that these fans and probably filters have never been replaced or cleaned. The dB level is really becoming outrageous. There are 3 items that I want to specifically point out of safety interest: 1. The obvious difficulty hearing ATC on the radio and other crew members on the intercom 2. There are certain possibilities of long-term hearing damage 3. This noise also causes crews to turn the fan to 'standby' and perhaps forget about turning it back on. This obviously is not the correct position. It reinforces the enjoyment of not hearing the blaring noise of the fan; but eventually ruins the CRT screens.