Our dog, a beagle, does the same thing. He also barks when someone other than members of the family walk up the garden path, or comes into the house. He only stops once he's been allowed to meet and do a sniff test on the intruder. Once that's over with, he's happy to continue being his normal placid self.
It might be worth a try. I always ask the person if they mind being sniffed at by him as I'd imagine it doesn't suit everyone. But once explained, no one has yet refused.
Cheers
