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Hidden Hearing Loss

Hidden Hearing Loss Could Affect a Quarter of People

Do you worry at the prospect of an evening in a pub or restaurant that insists on blaring out loud music? You're most definitely, not alone!

Do you struggle to understand the person next to you above the background chatter at dinner parties or in a restaurant? Do you worry about the prospect of an evening in a pub that insists on blaring out loud music? You're not alone, several surveys suggest that more than a quarter of us have great difficulty understanding speech in a noisy environment. In fact even if you pass a standard hearing test, you may still be suffering from something called "Hidden Hearing Loss".

 

Hidden Hearing Loss

Coined in 2011 by researchers at University College London, hidden hearing loss refers to the kind of difficulties that are not detectable via standard hearing tests (pure tone audiometry). David McAlpine, a professor of auditory neuroscience at the UCL Ear Institute in London has said:

People with this problem often have difficulty with complex listening tasks, such as deciphering speech among background noise. "This could be true of anyone with hearing loss. The difference with hidden hearing loss is that they don't necessarily have trouble hearing quiet sounds when there is no noise in the background, so the results of an audiometry test look fine.

While it appears that your hearing levels are fine, this problem can still make social and work life frustrating. The worry is that with increasing exposure to noise in daily life, on personal music devices, for example, hidden hearing loss is potentially on the rise.So what is it and why have we changed our testing protocols to try and pick it up?

For years, sensorineural hearing loss was understood by us to mean damaged hair cells in the inner ear (cochlea). These hair cells are part of the chain that allows us hear and they may wear out with age. They can also become damaged by noise exposure, while sometimes that damage is just temporary. Your ability to detect faint sounds may be impaired for a few days after a concert or prolonged exposure to loud noise. However, it returns to normal as the hair cells recover, this is known as a temporary threshold shift.(TTS) It appears from recent research though that noise may actually cause irreversible damage to the connections (called synapses) between hair cells and nerve cells in the cochlea. This interferes with the sending of information to the brain. This is thought to be what's going on in hidden hearing loss.

Animal studies at Harvard found that in mice who were briefly exposed to loud noise, their sensitivity to quiet sounds was reduced for a few days. An expected TTS, however what was not expected was the discovery that the mice had permanently lost half the connections between the hair cells and the auditory nerve fibres in a large region of the cochlea. The damage is thought to occur because over- stimulated hair cells produce an excess of a chemical called glutamate. This chemical is toxic in large amounts to those synapses. Scientists hope to one day be able to reverse this damage by treating the surviving neurons withneurotrophins (molecules which promote healthy nerve growth), injected through the eardrum.

 

Tests For Hidden Hearing Loss

There is no test currently available to diagnose this damage and as we have said, pure tone audiometry ma y actually show normal hearing ability. One promising approach is based on tests of the auditory brainstem response (ABR). This is a measure of the electrical activity in parts of the brain involved in hearing. A pilot study by scientists at the University of Manchester, including Professor Chris Plack, using a variant of the ABR test on students with normal results on their standard hearing tests, found poorer brain responses among those who had been exposed to loud noise in clubs.

The tests that were used however, are not readily available outside scientific research. We have always been aware of problems akin to hidden hearing loss. There are differing problems that have been named Auditory Processing Disorder discovered and discussed over the years. This is why we use the battery of tests that we do in our hearing tests.They involve speech testing and speech in noise testing among others, this allows us to detect issues that may not be immediately obvious with a standard pure tone test. 

 

Comprehensive Hearing Tests in Cork

This allows us to comprehensively test your hearing ability, those tests also allow us to deliver real benefit for hearing aid users. It allows us to better customise their hearing aids to their hearing loss, it also allows us to make better recommendations to our customers. If you want to talk to us about your hearing, hearing aids or hearing healthcare, give us a call 0n 1800 501 501 or come and see us in our hearing aid centres in Cork, Waterford, Kilkenny & Tralee.

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