What a bad wheel bearing sound like?

[sasha055]

Hi,

I have a bad wheel bearing I beleive...
I can hear a "whooo" sound from my rear left when I'm going over 50mph.

It's not very loud, with the top down I can't hear it (I can if I listen for it.) however with top up I can hear it clearly...
It quiet before 45-50mph... it gets louder when I go over 70..

Is it a bad bearing? how can I test it?
I would really like to be sure that it's a bad bearing before dropping 300$++ for SIR tools to replace it.

Any advice on what that sound could be?

Also is there anyone in Seattle area that have the tool and will be kind to let me borrow it? or sell me a used one?

Thanks
Sasha