Man can't hear in a crowded restaurant.

Sometimes when a person has a difficult time hearing, somebody close to them insultingly suggests they have “selective hearing”. Perhaps you heard your mother accuse your father of having “selective hearing” when she believed he was ignoring her.

But in reality it takes an incredible act of teamwork between your ears and your brain to have selective hearing.

The Stress Of Trying to Hear in a Crowd

Perhaps you’ve experienced this scenario before: you’re feeling burnt out from a long day at work but your friends all really want to go out for dinner and drinks. They pick the loudest restaurant (because it’s trendy and the deep-fried cauliflower is the best in town). And you strain and struggle to follow the conversation for the entire evening.

But it’s very difficult and exhausting. And it’s a sign of hearing loss.

Maybe, you rationalize, the restaurant was simply too noisy. But no one else appeared to be having difficulties. It seemed like you were the only one experiencing difficulty. Which gets you thinking: what is it about the crowded room, the cacophony of voices all struggling to be heard, that throws hearing-impaired ears for a loop? It seems as if hearing well in a crowd is the first thing to go, but why? Scientists have begun to reveal the solution, and it all begins with selective hearing.

Selective Hearing – How Does it Work?

The scientific name for what we’re loosely calling selective hearing is “hierarchical encoding,” and it doesn’t take place in your ears at all. This process almost entirely takes place in your brain. At least, that’s according to a new study performed by a team from Columbia University.

Scientists have known for quite a while that human ears essentially work as a funnel: they gather all the impulses and then forward the raw information to your brain. In the auditory cortex the real work is then accomplished. That’s the part of your brain that handles all those signals, interpreting sensations of moving air into recognizable sounds.

Just what these processes look like was still unknown in spite of the existing understanding of the role played by the auditory cortex in the hearing process. Thanks to some innovative research techniques involving participants with epilepsy, scientists at Columbia were able to learn more about how the auditory cortex functions in terms of picking out voices in a crowd.

The Hearing Hierarchy

And here is what these intrepid scientists discovered: the majority of the work performed by the auditory cortex to isolate distinct voices is done by two separate parts. They’re what enables you to separate and enhance specific voices in loud settings.

  • Heschl’s gyrus (HG): This is the part of the auditory cortex that manages the first phase of the sorting routine. Heschl’s gyrus or HG breaks down each individual voice and separates them into distinguishable identities.
  • Superior temporal gyrus (STG): Eventually your brain will need to make some value based choices and this happens in the STG after it receives the voices that were previously differentiated by the HG. Which voices can be safely moved to the background and which ones you want to pay attention to is determined by the STG..

When you have hearing problems, your ears are missing specific wavelengths so it’s more difficult for your brain to differentiate voices (depending on your hearing loss it could be low or high frequencies). Your brain can’t assign individual identities to each voice because it doesn’t have enough data. It all blurs together as a result (which makes interactions difficult to follow).

New Science = New Algorithm

It’s standard for hearing aids to have features that make it easier to hear in a crowd. But hearing aid manufacturers can now include more of those natural functions into their algorithms because they have a better idea of what the process looks like. For example, hearing aids that do more to differentiate voices can assist the Heschl’s gyrus a little bit, resulting in a greater ability for you to understand what your coworkers are saying in that noisy restaurant.

The more we understand about how the brain works, specifically in connection with the ears, the better new technology will be able to mimic what takes place in nature. And better hearing outcomes will be the result. That way, you can concentrate a little less on straining to hear and a little more on enjoying yourself.

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