Can I use Airplay without Apple TV or Airport I have my PC, IPad and a AirPlay compatible speaker

My question is:

Can I use AirPlay to hear my IPad music in my speaker only with ITunes software only, or I need necessarily to buy AppleTV or an AirPort in order to use AirPlay?  

In order to use AirPlay is necessarily to have AppleTV o an AirPort??
Rogue Amoeba has a few applications that work together for this sort of thing. Check out Airfoil: http://www.rogueamoeba.com/airfoil/