Helium reveals gibbon’s soprano skill

Apes are unlikely to become virtuosos at the opera house, but gibbons have naturally mastered some of the vocal techniques that human sopranos rely on, scientists in Japan report.

The research shows that, like humans, gibbons use a ‘source–filter’ mode of sound generation. The sound originates from the creatures’ vocal folds as a mixture of different harmonics, which are multiples of the frequency at which the vocal folds vibrate. The resonant frequencies of the vocal tract then determine which of these harmonics are projected. By altering the position of the mouth, lips and teeth, humans vary these resonant frequencies to make the different sounds required for speech.

The gibbon’s melodious calling bears many similarities to the techniques of human singers. Like professional sopranos, gibbons tune the resonant frequency of their vocal tract to the pitch frequency generated by the vocal folds to amplify the sound. Acoustic physicist Joe Wolfe of the University of New South Wales in Sydney, Australia, says that this type of “resonance tuning” is something that comes fairly easily to human singers and is key to their ability to project their voice over a loud orchestra.