Have you ever been in a situation where there is a lot of background noise, for example dining out with friends in a busy restaurant, and while your hearing is usually fine, you struggle to make out what they are saying? It could be hidden hearing loss, also called hidden hearing disorder, a term used to describe a specific hearing problem in which you can hear just fine in quiet or normal settings but have difficulty when there’s competing background noise.
Experts say many people have this disorder (which can coexist with tinnitus and hypersensitivity to sound) and don’t know it. And the condition can’t always be detected in the quiet testing room for an audiogram — the gold-standard test of hearing sensitivity. As part of research conducted at Massachusetts Eye and Ear, study authors reviewed more than 100,000 patient records over 16 years and found that about 1 in 10 who visited the audiology clinic had complaints of hearing difficulty; yet auditory testing revealed they had normal audiograms.
Most researchers feel that long exposures to even low-level noise may cause hidden hearing loss. In our daily life, there are more mechanized devices creating background noise and the amount of time and level of noise in our environment have combined to create hidden hearing loss.
What’s going on in our ears — and in our brain
Hidden hearing disorder occurs when the connections between the hair cells in the inner ear and the nerves that carry hearing signals to the brain are lost, so information can’t be transmitted. As a result, the brain is getting an incomplete signal. Standard hearing tests can’t detect these changes that hinder our ability to hear in louder settings. In fact, you can lose nearly 90 percent of the electrical connections before a doctor is able to see an irregularity.
However, when it comes to hidden hearing loss, some researchers believe that we should shift our attention away from our ears and toward our brain.
“There is a widespread misconception that the ear and the auditory nerve synapses hold all the answers about why we struggle with hearing as we age,” Polley observes. “This is not the case. The brain creates the perception of sound, and measures of the brain function will be able to predict hidden hearing disorders more accurately than measures of the ear, because the brain is the arbiter of sound perception, even if the problem begins in the ear.”
To that end, Polley and his colleagues at Massachusetts Eye and Ear have been working to “find a biomarker for hidden hearing disorder, so that we can focus on the neurological cause for the complaint.”
Diagnosing hidden hearing loss
Though standard pure-tone audiograms may not be able to detect hidden hearing disorder, the only way to detect hidden hearing loss is to see an audiologist to have a comprehensive audiological evaluation.
Tests that can demonstrate evidence of hearing damage include an extended high-frequency pure-tone audiogram; an otoacoustic emissions (OAE) test, which examines how well your inner ear is functioning by measuring otoacoustic emissions (sounds the inner ear emits when responding to another sound, which can show early-stage damage); and speech-in-noise tests, designed to simulate real-life conditions.
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