MIT Study Reveals Why Ears Are Extremely Sensitive To Different Sounds

Posted: Jan 25 2019, 3:21am CST | by , in Latest Science News


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MIT Study Reveals Why Ears are Extremely Sensitive to Different Sounds
Credit: MIT micromechanics group

The size, stiffness and distribution of nanoscale pores in inner ear make whole hearing system highly selective.

Human ears are extremely sensitive to sounds and can detect vibrations moving less than the width of an atom. But the underlying mechanism responsible for this selectivity is not fully understood. A new analysis, conducted by MIT researchers, provides more insights into the hearing ability of humans and reveals how ear achieves the amazing ability to pick up faint sounds.

The ear’s ability to sense and distinguish different frequencies of sound depends on a tiny structure in the inner ear called the tectorial membrane. MIT researchers have been studying tectorial membrane for years. The size, stiffness and distribution of nanoscale pores in that gel membrane controls the movement of water within the structure. Now, researchers have revealed the mechanism by which these tiny pores filter or sorts sounds.

The tectorial membrane lies at the top of hairs inside the cochlea or inner ear. These sensory receptors are arranged in a specific way. This means that each is sensitive to different frequencies of sound. Since tips of those hairs are embedded in the tectorial membrane, the behavior of gelatinous structure strongly affects the way those hairs respond to the sounds coming into ear.

“Mechanically, it's Jell-O,” said researcher Dennis Freeman. “If you squeeze it as hard as you can, you can't get the water out. It's held together by electrostatic forces.”

Detailed analysis of the microscopic structure showed that pores within tectorial membrane affect how water within the gel moves back and forth between pores in response to vibration, making the response of the whole system highly selective. Both the highest and lowest frequencies are less affected by the amplification coming from the tectorial membrane, while the middle frequencies are more strongly amplified.

The new details help explain the ear's remarkable ability to distinguish sounds with subtle differences and could lead to improved systems for restoring hearing.

"The mechanical nature of the nanoscale structures of the inner ear is extremely hard to study but critically important to hearing,” said John S. Oghalai, a professor at the University of Southern California. “In this study, the authors show that the proteins within the tectorial membrane and the fluid interspersed between them are 'tuned.' This may finally explain how each hair cell is stimulated at its correct frequency."

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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