They're both onomatopoeias, from the greek onomatopeiia, "Onoma=Name and Poeio=to make" basically using words that imitate the sound they denote. I guess that to be able to answer this, you should be paying more attention to the guy's face instead of what's actually coming out of his mouth. If this helps, in almost all spanish speaking countries we use "eh?" to express you haven't understand. But I've never heard "huh?" in spanish. And I actually haven't heard "eh?" in english, but I've defintately seen it written. Does this make sense to anyone?

Not much difference. However, "eh" is used more commonly in Canada than "huh" is, and "huh" is used more commonly in the USA than "eh" is. Granted, with each generation, the usage in the two countries becomes more and more congruous.

���Eh” and “Huh” are both spoken interjections and have the same meaning. Although the use of eh is regarded by some as characteristic of Canadian English, most usages of eh are spread throughout the English-speaking world, in the meaning of "Huh?", "What?", "Hey", or "Repeat that, please". It is an invariant question tag, unlike the "is it?" and "have you?" tags that have, with the insertion of not, different construction in positive and negative questions. There is some question as to the origin of the term, a popular theory is that the "eh" sound is similar to the "ey" sound that a native French speaker will stereotypically say when pronouncing the word "Hey". In addition, "eh" can also be used as an exclamation: "He's all right, eh!" This has its origins in Scotland, where it can still be heard. It can also mean "I don't care" or "whatever", when pronounced as it is spelled (not like "ey", but an unstressed "eh"). http://en.wikipedia.org/wiki/Eh Huh Used to express surprise, disbelief, or confusion, or as an inquiry inviting affirmative reply, disdain or lack of interest, or used to reinforce a question.Origins are American 17th century slang.