hey guys my alternator is humming when i start up my car from a cold start, how can i fix this, the alternator is only a couple of months old though, car is a 93 accord

 

Alternators will often whistle when they are under heavy load, and this is a trait which is cinsidered normal.
But if it's humming, that could be a whole different thing.
Have the alternator load tested (DeathZone Auto Parts Ect.)

Either you've a bad bearing (it would do it all the time (however))
or
One of the three 'phases' (It's actually three rectified alternators in one) has gone south and sets up an uneven load as it spins (heard as a hum)
It will show up as a reduction from the rated output by factors of 1/3. IE: 100amp rated will only put out 66 or 33amps....or none.

P