bro first of all, thats not fan belt. there isnt any fan belt fans are not run by seperate motors instead of belts.so this sound can be of two things, either clutch bearing or the belts on the left side of the engine, the charging belt etc. u can do a very small test to see if the belts are squeeling or not.start ur car in the morning, take a little water and throw it over belts.if they are the culprit, the sound wud go out for a second or two.
once diagnosed, there are 3 things u can do.
1st is, change it! that isnt neccessary unless ur car has done tooooo much miles.
the 2nd solution is to apply some grease on the belts.yes, grease.no it wont make then slip.i ve done that countless times with mine.but this is also a temporary fix.the best one is to get the belts adjusted.my mechanic did that for me n i ve go no belt noise for the past 30,000kms. im not really sure what he did but i think he readjusted the placement of generator, moved it a bit to tighten or losen the belt. that fixed it.