[Above: Two bottlenose dolphins swimming around. Image via Max Pixel and Creative Commons CC0 license.]
Human speaking voices come in a dizzying array of tones. They can be raspy or reedy, lilting or monotone, chirpy or sonorous, nasal or throaty, breathy or booming, and that’s before we even start describing accents.
Most mammals, including humans, use their vocal tracts to make noise, and so slight variations in the anatomies of our voice boxes, throats, mouths, and nasal passages give our voices unique timbres.
Perhaps, not surprisingly, we can use variation in vocal qualities to tell people apart. (Some people have a lot more acuity at this than others, but most of us can recognize our favorite singers, even on songs we haven’t heard before, and distinguish our dog’s bark from the neighbors’ yapping.)
“If you answer the phone, and it’s someone you know very well, you know the voice, and they don’t have to tell you their name,” explains behavioral biologist Laela Sayigh of Hampshire College. “That’s how really every other mammal that has ever been studied identifies each other.”
With one notable exception–dolphins.