Noise, Birds and Hearing

12/3/2021

Recently while waiting for a bus, my ears were assaulted simultaneously by the

sounds of construction equipment, sirens, car horns and the whiz of traffic. My ears hurt.

Yet, when I saw two sparrows pecking on the sidewalk for food, I noticed that they seemed oblivious to all the noise.

I thought to myself, “How could such small creatures (a sparrow weighs approximately 0.85 – 1.4 ounces) with

ears that are tiny holes on the side of their heads covered with feathers, withstand such a high frequency of

noise.

I then thought, “Is it possible that these birds are deaf?”

I discovered that I’m not the only one intrigued by birds and their hearing.

Stanford University scientists are actively studying why birds never go totally deaf yet we humans do.

Their research is showing that birds can regrow damaged hair cells in their inner ears - an amazing anatomical feat.

So where exactly are these hair cells located and how do they work?

First, let's look at the anatomy of the human ear.

The ear is made up of three parts: the outer ear, the middle ear and the inner ear. These microscopic hair cells,

which birds can regrow, are located in the cochlea of the inner ear. The cochlea is shaped like a small snail

and is about the size of a pea. It is fluid-filled and lined with these tiny hairs (there are about 15,000 in the human ear)

Vibrations are transmitted as waves from the outer ear to the eardrum. The eardrum passes the vibrations along

through three tiny bones, the malleus, incus and stapes. They pass vibrations to the cochlea. The vibrations

pass through the cochlea fluid and over the tiny hair cells in a wave-like motion creating electrical signals

which are sent to the brain via the via the cochlea nerve. At the end of this process, we are able to hear

the sounds created by the initial vibrations from our outer ear.

Healthy hair cells can be likened to wheat standing tall in a field. In humans, these tiny hair cells die

for various reasons: injuries, aging and loud noises.

Dead hair cells look like a wheat field pelted by heavy rain which don’t grow back in humans.

Scientists are working to unravel this mystery of how birds can regenerate cochlear hair cells. And the discovery and

identification of gene mutations related to cochlea hair cell degeneration, offers another avenue to pursue in their quest to

find a way to regenerate healthy hair cells.

If, and when they do, it holds out the promise that one day we could be like our feathered friends and never

go permanently deaf.

I hope this post gives you a renewed appreciation of the sense of hearing, how our ears work and the wonder of birds.

White, Tracie. "To hear again: birds regrow damages inner ear cells. Why can't we?" Listening: the art and science of hearing, Stanford Medicine, 2018
stanmed.stanford.edu/listening/scientists-hope-cure-hearing-loss-studying-birds.html.