Aug 20 2014
My visit to an audiologist for a baseline hearing test revealed an awesome thing about birds.
This summer I had my hearing tested because I noticed I could still hear faint rustling sounds with my right ear but not with my left. For a long time my left ear has been slightly “less good” but this spring was the first time I didn’t have stereo for everything. I was looking in the wrong direction for the very quiet birds.
The hearing test showed that my right ear is still above average but I’ve begun to age and am very slowly losing the top end of sound. My left ear has lost more than my right — hence the lack of stereo — but for a human I have good hearing. The sounds I’ve lost would only be noticed by a cat (or a birder). Since those sounds aren’t in the “human” range, the loss is not correctable.
But if I was a bird, I could correct it myself.
We hear thanks to tiny “hair cells” that line the cochlea of our inner ear. Not “hairs” at all, they are actually protein-filled protrusions that vibrate when sound reaches them and transmit it electronically to the brain. Age, loud noises, and toxins, including strong antibiotics, damage these cells. Mammals cannot regenerate hair cells. Birds can!
The photo above, from a 2004 article at the University of Washington’s Department of Medicine, shows the man who discovered this with a bird that helped him prove it. In the late 1980’s Dr. Edwin Rubel at the University of Washington and Dr. Doug Cotanche at the University of Pennsylvania simultaneously discovered that birds can recover their hearing. After hair cell loss they grow the hair cells back again! Later research uncovered this same ability in fish. (Click here for the 2004 UW article and here for information in the 2012 Hearing Journal.)
Their discoveries have led to work on a wide range of possible solutions, none of which are perfected yet.
For now, I compensate when I hear a faint bird sound — I turn my head.
Some day, thanks to birds, there may be a cure for us mammals.
(photo of Dr. Edwin Rubel from a 2004 article about his research at the University of Washington Department of Medicine)