98' ford taurus makes humming/buzzing/whining sound

My ford taurus makes a weird sound when I am driving it, it doesn't make the noise when i first turn it over, only when i start to drive, also it seems to get worse while making turns, my power steering fluid was low and i refilled it, but I'm not sure what it could be...please help! also it seems to stop after i have been driving it for a while.