Photo credit: Sepehr Ehsani licensed under CC BY-NC-ND 2.0

by Daniel Fink, MD, Chair, The Quiet Coalition

This press release from Boston’s Massachusetts Eye and Ear Infirmary reports on the award of a large NIH grant to Sharon Kujawa, PhD, Charles Liberman, PhD, and others there. Why is this important? Because in 2009, Kujawa and Liberman published the first report describing cochlear synaptopathy caused by noise exposure in an animal model.

Sound is transmitted through the ear to the cochlea, deep within the temporal bone of the skull, where minute hair cells perceive the transmitted sound waves and transduce the sound waves into electrical signals. The electrical signals pass through connections, called synapses, and are transmitted to the auditory processing centers in the brain, where they are perceived as sound.

It turns out that high-intensity sound damages the synapses. This doesn’t just happen in animals, but has now been shown to happen in humans, too.

This discovery is thought to explain a phenomenon that had been observed for years, the difficulty adults in mid-to-later life have understanding speech in noisy situations, e.g., a noisy restaurant. But when a patient complains of this to the audiologist, hearing testing, i.e., pure tone audiometry, their test results will be within or largely within normal limits.

That’s why the cochlear synaptopathy is called hidden hearing loss. The hearing test may be normal, but more sophisticated research techniques demonstrate that auditory damage has occurred.

We congratulate Dr. Kujawa, Dr. Liberman, and their colleagues, and look forward to reading future publications from them.

In the meantime, however, no more research is needed to know that noise is unwanted and/or harmful sound, and that a quieter world will be a better and healthier world for all.

Because it it sounds loud, it’s too loud, and your auditory health is at risk.