According to a paper published in PLOS One, a team of linguists say that the word 'huh?'is the one syllable that is universally recognized throughout the world.

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Previous studies claimed that words like "mama," "papa," and "um" were also well recognized, but none of their results were convincing as "huh." Here's more from the New York Times:
The study, conducted by Mark Dingemanse, Francisco Torreira and Nick Enfield, closely examined variations of the word — defined as “a simple syllable with a low-front central vowel, glottal onset consonant, if any, and questioning intonation” — in 10 languages, including Dutch, Icelandic, Mandarin Chinese, the West African Siwu and the Australian aboriginal Murrinh-Patha.

The researchers also looked at other words and expressions used to elicit clarification during conversation, a function that linguists refer to as “other-initiated repair.” But only “Huh?,” they write, occurs across languages whose phonetic patterns otherwise vary greatly.
Huh, you don't say. So what is it about the word "huh?" that makes it such a big deal?
It might seem trivial to carry out research on “Huh?,” which some linguists argue isn’t really a word at all. But the study, Dr. Enfield said, is part of a broader effort to challenge the dominant view that language is primarily a matter of inbor grammatical structure, as Noam Chomsky has argued. Instead, some researchers suggest, language is primarily grounded in social interaction.

“We think of this as the core of language: managing common understanding as we talk,” Dr. Enfield said in an interview. Confirming and checking with other people, he added, “are really fundamental to the use of language.”
So the next time you're stuck in a foreign country and trying to talk your way out of something, just say the word "Huh?" over and over again. Eventually, someone will be able to understand you.