sounds like a typical loose drive belt noise. few things will cause it.. 1) water introduced into the pulley/belt area ( like after the engine has been steam cleaned) 2) loose a/c, alternator belt which are very easily tightened up again.
it's a simple diy job if ur mechanically inclined and have the right tools, otherwise any workshop can tighten them up for not much at all.
last option is to lubricate the belt using WD-40 or a lube stick. just apply some on the belt itself and smear some on the pulleys. lastly, inspect the belt.. if it's cracked and ripped, I'd suggest getting it replaced asap as the last thing u want to happen is to have the power steering belt break off while doing a hard corner :D