Thanks for all the replies. I'm really bad at soldering so to me that's not really an option. I thought possibly the firmware might be dated but it turns out I have the latest one. 
I'll try replacing the fan. If that doesn't work I don't know what I'll do. Maybe turn it off at night.
I tried using one of my PC case's fans but it didn't fit. It's weird. The fan from my PC case has a 4 pin connector but it's a different 4 pin connector. Maybe because the one from the Antminer is a higher powered fan? I'll try to go at my local computer store and see if they have that model of fans.
I'll try replacing the fan. If that doesn't work I don't know what I'll do. Maybe turn it off at night.
I tried using one of my PC case's fans but it didn't fit. It's weird. The fan from my PC case has a 4 pin connector but it's a different 4 pin connector. Maybe because the one from the Antminer is a higher powered fan? I'll try to go at my local computer store and see if they have that model of fans.
Ok maybe i went to far with this soldering.
Try this simple thing-cut red wire and put 47ohm resistor from one end to other end of red wire.
Once this is done max voltage on fan will be cut at least in 1/3 so this will slow down this fan and will make it more quiet.
But there is down side of it- if miner will got hot fun will not speed up to cool it.
I will make few photos and will show you how easy it is.
replacing a fun will not help as probably :
a. controller is fucked and gives order to full speed for fun-so dosnt matter what fun you will use it will spin full speed.
Try to connect to other blade same fun and see if this will help. Maybe just simply changing blade will help.