The scans revealed that a tubelike part of the dinos' inner ears called the cochlea was sensitive enough to detect low-frequency sounds produced by the crests.
The team also scanned the skulls of individuals of various ages within each species and found that as the dinosaurs matured, their crests grew and their nasal passages changed shape.
"The youngsters have just the beginnings of a crest and slightly expanded airway," said study team member Lawrence Witmer, a paleontologist at Ohio University.
"As they get older, they start to develop a much more convoluted airway and a taller crest."
The changes varied between individuals, so the nasal cavities may have been as unique as human fingerprints.
As a result, the duck-bills may have had voices unique enough to tell one another's calls apart, the team speculates.
The images also show that brain regions associated with higher cognitive functions were larger than previously thought, possibly giving the animals the brainpower needed to ID and decipher calls.
The brain scans add to recent finds that weaken the theory that the crests were used to boost sense of smell.
Previous research by a team at the University of Texas had found that the nasal cavities inside the crests couldn't detect odors because they didn't contain nerve tissues.
Likewise, the new study revealed that the region of the brain that controls smell was too small for the dinos to have processed so much extra information.
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