The Associated Press (AP) reports that “[s]cientists have been finding evidence that loud noise — from rock concerts, leaf blowers, power tools, and the like — damages our hearing in a previously unsuspected way.” The damage “may not be immediately noticeable, and it does not show up in standard hearing tests,” the AP adds, but according to Harvard researcher M. Charles Liberman,” it can rob our ability to understand conversation in a noisy setting [and] may also help explain why people have more trouble doing that as they age.” The condition is called “hidden hearing loss,” and Liberman adds that “[n]oise is more dangerous than we thought.”
The AP interviews Matt Garlock, a 29-year old systems engineer who is “a veteran of rock concerts.” Garlock complained of not being able to hear friends in a crowded bar, but when he got his hearing checked his test results were normal. The AP writes that Liberman’s work “suggests that there’s another kind of damage that doesn’t kill off hair cells, but which leads to experiences like Garlock’s.” Specifically, Liberman believes that loud noise damages the delicate connections between hair cells, called synapses. He adds that animal studies show that “you could lose more than half of your synapses without any effect on how you score on an audiogram,” but if you lose enough synapses, it “erodes the message the nerves deliver to the brain, wiping out details that are crucial for sifting conversation out from background noise.”
The end result is that people like Garlock recognize that they have a problem but their hearing appears to be fine when they take conventional hearing tests. Fortunately, Liberman says that “[o]ne encouraging indication from the animal studies is that a drug might be able to spur nerves to regrow the lost synapses.” [Note: This article notes that Liberman has a financial stake in a company that is trying to develop such treatments.] But while treatment for hidden hearing loss may be available in the future, what can be done now? Liberman states that his work “lends a new urgency to the standard advice about protecting the ears in loud places.” As always, prevention is better than treatment.