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Our understanding of hearing loss and the underlying mechanisms have improved greatly over the last few years, something that has led to a re-evaluation of long-held beliefs. Conventional thinking has taught us that a single exposure to loud noise is not harmful to the ears over a long time and that only sustained, repetitive noise damage has the potential to cause hearing loss.
One of the shocking facts that have recently caught a lot of attention is that even a single exposure to loud noise, such as that experienced during a concert, is enough to cause permanent damage to your hearing.
Noise-Induced Ear Damage: A Traditional View
The old theory of hearing loss caused by excessive noise postulated that the hair cells lining the inner ear get damaged by excessive vibrations, leading to hearing loss. These hair cells are exquisitely sensitive and are irreparable. Studies testing out this hypothesis found results that were in line with it, concluding that hair cells are unlikely to be damaged in a single high decibel event and instead may take years or even decades to be damaged by this method.
Recent Evidence Challenges The Idea That Your Ears Are Safe If You Only Go To Concerts Occasionally
Now, however, animal studies and a few human studies have shown that while these hair cells survive for a long time, the nerves that transmit the signals from the cells to the brain may not be that lucky. These studies have found convincing evidence that permanent damage can be caused just by a solitary exposure like attending a musical concert.
The pioneering work in this field has been done by neuroscientists M Charles Lieberman and Sharon G, who have been studying noise-induced hearing loss for the better part of their careers. One of the reasons why this nerve damage was not known earlier was because stains to isolate them as they degenerated simply did not exist, thereby making animal studies and collecting histological evidence impossible.
Hearing Loss Hypothesis
Lieberman and Sharon have put forward the hypothesis that even a single exposure to loud noise can cause degeneration and death of nerve fibers that connect the hair cells and the brain. This degeneration, they say, is caused by an over-production of glutamate. This acts as a neurotransmitter and a chemical signaling compound in normal conditions, however it plays a role in degeneration when produced in larger quantities.
This degeneration and loss of hearing is also not discernible in normal audiograms, since the partial degeneration of some of the nerve fibers is not enough to cause severe enough hearing loss to show up on these tests. Our brain compensates for some of the hearing loss and adapts so people often experience a return of hearing abilities to normal after an initial few hours where cotton seems to have been stuffed in their ears.
This however, does not mean that it should be ignored; it just means that our current testing methods need to be more sensitive. This hypothesis is backed by some convincing animal studies and is expected to cause a significant shift in the way hearing loss is studied by scientists all over the world. A lot more work and human studies will be needed to quantify the ramifications of these findings.