Mar 19 2012

Howard Hughes Medical Institute: "The Science of Sound"

LINK HERE to visit the HHMI Lecture

Dr. Hudspeth explains the basis for the ear’s remarkable ability to detect sound through the hair cell, the sensory receptor found in the inner ear.

The Howard Hughes Medical Institute educational outreach project targets audiences ranging from little kids to med students. Some of the essays from Seeing Hearing and Smelling the World seem particularly directed at someone doing a school paper on the senses; they provide an understanding of the basic facts.

Others are more particular.

Signals From a Hair Cell, is an entertaining essay on the importance and amazing powers of ear cilia. Signals offers the reader a vibrant description that not only aids comprehension, it makes ear cilia memorable.

Highlights from the essay:

There are 16,000 hair cells in a human cochlea compared to some 100 million photoreceptors in the retina of the eye.

They are extremely vulnerable and sensitive.

Researchers calculate that hair cells are so sensitive that deflecting the tip of a bundle by the width of an atom is enough to make the cell respond.

Based on data from thousands of experiments in which they wiggled the bundle back and forth, the researchers calculated that hair cells are so sensitive the infinitesimal movement, which might be caused by a very low, quiet sound at the threshold of hearing, is equivalent to displacing the top of the Eiffel Towereiffel by only half an inch.

The photoreceptors in the eye are much slower, [says HHMI researcher, James Hudspeth],

“The visual system is so slow that when you look at a movie at 24 frames per second, it seems continuous, without any flicker. Contrast 24 frames per second with 20,000 cycles per second. The auditory system is a thousand times faster.”

 

 

 

 

photo credit: Scott Barrows, National Geographic
explore HHMI’s Seeing, Hearing and Smelling the World

 

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