countries use the "b" sound depending where it falls in a word. By the way, it's really a hybrid sound between "v" and "b" and is hard to master. So, the word "vaca" is usually a hard "v" sound but I've heard some pronounce it with a softer "b" sound too. A word like "television" I've never heard it with the "b" sound. I'm sure there is some rule out there but your best bet is soften the "v" sound a bit and stick with that.