Why would researchers in Japan induce gibbons to inhale helium? To record their high-pitched singing, of course. The differences between helium and helium-free singing revealed that gibbons actively control the vibrations of their vocal cords just as humans do, allowing the primates to communicate from more than 3 kilometres away. The gibbons’ technique is the same one soprano opera singers use to amplify high notes, suggesting that the physical traits necessary for speech aren’t uniquely human.
Here’s what a gibbon sounds like before and after inhaling helium: