remery said..
Yes, you hold one end of a tube near (emphasis on near) your ear, and the other end next to each of the carburettor's Inlet throats. Adjust the slide/butterfly Inlet so they sound the same.
I get what you're saying and it sounds plausible, but I think I really need to know what would Carantoc do? Sure, other people have used the sound to balance carbies, but he has probably got some strange reason for it not being the best way. I am only after the best way.
No doubt there have been cases where people used hoses and the mixtures were way off and those people survived but they probably have long term after effects from the tuning of the carbys.