Imagine you can't talk but can still vocalize - your mouth is full, or you're at the dentist's or something. You want to express "yes", "no" or "I don't know". You would express "yes" by nodding your head and saying "mmm-hmmm" with an ascending pitch. You would express "no" by shaking your head and saying "nnnn-nnn" with a descending pitch. You would express "I don't know" by shrugging your shoulders and saying "mmm-mmm-nnn" with an ascending pitch followed by a descending pitch, the same pitch pattern that you woud use to say "I don't know."

Now take the body language, leaving only the vocalizations. Those vocalizations still communicate the concepts of "yes", "no", and "I don't know" to English speakers. What I'm wondering is whether they translate. I don't think the "I don't know" vocalization translates as well, because it's "Je ne sais pas" or "Ich weiss nicht" or "No se", all of which have different pitch patterns. But would "mmm-hmm" and "nnn-nnn" translate?