How to stop the SMPS fan Noise?

It is tricky process and do it on your own risk. If you are sure the noise is coming from SMPS then unplug it wait for 5 minutes open it and remove the fan from it. Rotate it by hand and see if has any broken thing if not clean it with a little paint brush and then remove the sticker on the motor of the fan which is covering the hole. Then pour one drop only(only one drop or the whole assembly of the fan will be flooded ) of machine oil in it. Rotate slowly with hand. apply the sticker back. and after 5-10 times of operation it will give no noise. I have tried this process on my 7 years old CPU fans and they are running great. 

Important Note: Also you need to remove dust from the power supply just don't touch any part with hand and remove dust only by soft brush not with blower or something like that. Again do it on your own risk and if you are not comfortable with this let the professional do it.