Sitting in traffic can expose a driver to intense irritation, as well as a range of sound frequencies. Humming engines typically emit low-frequency sounds, while car horns release high-frequency blasts. Emergency vehicle sirens are high-pitched, and the rumblings from large trucks are lower-pitched.
For most people, their ears are able to process these wide-ranging sounds and make sense of them. However, scientists don’t have a full sense of why this happens because they are still working to understand the mechanics of the inner ear.
A team of physicists recently took a novel approach to understanding how the cochlea processes different frequencies. They uncovered new intricacies that may explain how the ear is able to hear the softest of sounds.
The Mysteries of the Ear
When it comes to human hearing, scientists still have many unanswered questions.
“Hearing is pretty mysterious,” says Benjamin Matcha, an assistant professor of physics at Yale University.
Although physicists have a general road map of how the ear functions and communicates with the brain, researchers still don’t have a complete picture.
In comparison, physicists better understand the inner workings of the human eye, particularly in terms of how light passes into the eye, bends, and then converts into electrical impulses that supply the brain with information.
“The physics of hearing is actually pretty poorly understood as opposed to vision,” Matcha says. “There is a lot of biochemistry in vision that is complicated, and we don’t understand it well, but the physics part is well understood.”
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The Physics of Hearing
When it comes to the physics of hearing, researchers know that when sound reaches the cochlea, it is converted into electrical signals. Auditory hairs in the cochlea pass along the signals and communicate to the brain what the ear is hearing.
For loud traffic sounds, such as someone laying on the horn because the car in front of them has failed to realize the light is not going to get any greener, the hairs are forced to bend in response, and electrical signals are sent to the brain.
But how is the inner ear able to tune into the faintest of sounds? How does the cochlea pick up on those barely-there sounds and provide the brain with information? Matcha and his research team saw this as a physics question.
“Physics is useful for understanding hearing at the basic level because the cochlea has a way of separating sound into different types of frequencies, and this is related to a lot of concepts in physics,” says Isabella Graf, a principal investigator at the European Molecular Biology Laboratory in Heidelberg Germany and a former postdoctoral researcher at Yale University.
On the Low Frequency
In a 2025 study published in PRX Life, the research team took a mathematical model and applied it to a rendering of the cochlea. Although the mathematical model previously existed, this novel application allowed the research team to uncover a deeper complexity within the cochlea.
The team wanted to learn from the study how the ear can detect soft, barely-there sounds. But, their results took them in a surprising direction when they discovered the possibility of a set of low-frequency mechanical modes in the cochlea’s basilar membrane. These “extended set of modes” move together in response to sound. Whereas the first set, “localized” modes, are able to uncouple and move independently, the second set works collectively.
The results surprised the team, mainly because they set out to apply a previously used principle to the entire cochlea. And when they did discover the possibility of low-frequency mechanical modes in the basilar membrane, they were surprised it had not been previously identified.
“In a way, this was a bit of a surprise finding in the sense that we had tried to understand something else,” Graf says. “People have looked at various models of the ear, why have people not already seen these other types of modes?”
The possibility of low-frequency mechanical modes is meant to apply to people with standard hearing. Some people with hearing loss may be unable to hear quiet, low-frequency sounds like a car engine idling.
The research team hopes their findings contribute to a growing understanding of how the ear processes low-frequency sounds and that such work may help future researchers better understand why some people fail to hear well at different frequencies.
“This is basic science research, and it helps us better understand how a healthy ear works. This is helpful in understanding how to help impairment,” says Asheesh Momi, the study’s first author and a PhD student in the Department of Physics at Yale University.
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Emilie Lucchesi has written for some of the country's largest newspapers, including The New York Times, Chicago Tribune and Los Angeles Times. She holds a bachelor's degree in journalism from the University of Missouri and an MA from DePaul University. She also holds a Ph.D. in communication from the University of Illinois-Chicago with an emphasis on media framing, message construction and stigma communication. Emilie has authored three nonfiction books. Her third, A Light in the Dark: Surviving More Than Ted Bundy, releases October 3, 2023, from Chicago Review Press and is co-authored with survivor Kathy Kleiner Rubin.
