National Geographic News
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A extremely tall man uses a shorter man as an elbow rest for a portrait in 1930.

Kirn Vintage Stock

Marcus Woo

for National Geographic

Published December 6, 2013

Talk about a cool finding: You can tell the relative heights of others just by the sound of their voices, according to new research.

Past experiments have also suggested that people can discern height from voice. The new analysis not only confirms this ability but also points to what may be clueing in listeners: the sound produced in the lower airway below the Adam's apple—or the lump of cartilage that protrudes from the larynx. (Explore an interactive of the human body.)

The idea, explained study leader John Morton, a psychologist at Washington University in St. Louis, is similar to what happens when you blow air through a bottle.

If the bottle is bigger and taller, the sound is more resonant than if the bottle were smaller and shorter. But unlike with bottles, people aren't simply picking out deeper voices as belonging to taller people, Morton said. (Also see "Pictures: See and Hear Last Speakers of Dying Languages.")

Instead, they determine height based on subtle technical differences in sounds emanating from the lower airways, which are called subglottal resonances.

Heightened Voices

For the experiment, Morton and colleagues accessed data from the Washington University-UCLA speech corpus. That includes recorded voices as well as sounds from volunteers' lower airways, which were obtained by measuring vibrations with an instrument placed just below the speakers' Adam's apples.

They then had 24 volunteers listen to the recorded voices of people saying a few meaningless words. In the first task, the volunteers heard two voices and were asked to choose who they thought was taller. In the second experiment, the participants were asked to rank five people by height based on their voices. (Also see "Deep-Voiced Men Have Lower Sperm Counts, Study Says.")

After analyzing the data, Morton and his colleagues found a link between whether the volunteers could correctly select the shorter and taller speakers and small changes in subglottal resonances, suggesting that these sounds were how people distinguished height.

On average, people were accurate 62.7 percent of the time—significantly better than if they were just picking randomly.

"It says to me that it's a universal human trait or ability to do this," said Morton, who presented the research at the 166th meeting of the Acoustical Society of America in San Francisco on December 3.

Of course, the volunteers were listening to a person's entire voice and not just their subglottal resonances, Morton emphasized. Sounds from the vocal tract above the Adam's apple also contain some information about height.

To disentangle the effects of these subglottal sounds from other nuances in every voice—and to prove for sure that they're responsible for revealing height—is challenging, and will require more research, he said.

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