So reverberant chant in Bathari, a language spoken by perhaps a few dozen people in Oman, sounds alongside enigmatic footage of rock formations. A blurry figure walks in the distance, eventually covered by pages and pages of scrolling script, as we listen to the evocative Ahom language of India. A child speaks Light Warlpiri, which has a few hundred native speakers in northern Australia.

That we don’t see the speakers and can’t know what’s being said is the point of this austere and poignant Babel. The musical landscape is sometimes gentle, sometimes aggressive, but it always keeps our attention on the rich, incomprehensible, often overlapping chorus of words. The camera slowly approaches ghostly forests, bodies of water and, through space, our planet — imagery that suggests the language crisis interacts with, and is in part caused by, even graver threats to earth’s sustainability.

Ms. Herzog dates the origins of “Last Whispers” to more than 15 years ago, and her interest in languages even further — back to when, as a young girl growing up in Russia, she struggled to learn English to understand a Sherlock Holmes story that turned on the deciphering of a code presented as dancing stick figures.