Agreed - very likely wheel bearing.
They are a common failure item for this model. Not necessarily a unique problem for Porsche, however, as the same one is used for certain models of BMW and Mercedes, which may explain why the part itself is not expensive.
Someone noted that the same part was used on the 914, with tires half as wide and a whole lot less stress on the bearing...
The bearing size was increased in later models to account for this.
My first one failed after 95K miles; maybe I'm not stressing the bearings enough
This can be accomplished as a DIY, but I don't recommend it unless you are already a pretty decent mechanic with all the tools. The juice ain't worth the squeeze.
The good news is you can likely drive it without much immediate danger. If you are like most of us, you will decide you can't stand the noise long before your bearing fully implodes.