I had a similar sound when I first bought my SVX. I thought it might be my wheel bearings, but it most definitely wasn't. I had some tires left over from my previous SVX, so I swapped them on. Noise went away.

The original tires were quite ****ty. Some no-name brand. The replacements were Yokohama AVS type V-rated. Much bettah!

I would have a reputable tire shop look at your tires for odd wear and tear and leaks and bumps and humps. Everything. I might even look into seeing if any of the local shops have some used, but good condition tire replacements.

Or you could buy some new ones. Whatever. You just may want to consider what you can afford and/or what seems more likely to be the problem. Search to boards for info on the rear wheel bearings. This noise is very highly documented, trust me. If your noise isn't the same, you may wanna look at the tires. If it seems to fit the description for the bearings, do the bearings.

Seems to be somewhat of a craps-shoot.