Man can't hear in a crowded restaurant.

Sometimes when a person has a difficult time hearing, someone close to them insultingly suggests they have “selective hearing”. When your mother used to accuse you of having “selective hearing,” she was suggesting that you paid attention to the part about chocolate cake for dessert and (perhaps purposely) ignored the part about doing your chores.

But actually selective hearing is quite the skill, an amazing linguistic accomplishment performed by teamwork between your ears and brain.

The Difficulty Of Trying to Hear in a Crowd

This scenario potentially seems familiar: you’ve had a long day at work, but your buddies all insist on meeting up for dinner. They choose the noisiest restaurant (because it’s trendy and the deep-fried cauliflower is the best in town). And you spend an hour and a half straining your ears, trying to follow the conversation.

But it’s difficult, and it’s taxing. And it’s a sign of hearing loss.

You think, perhaps the restaurant was just too noisy. But no one else seemed to be struggling. The only person who appeared to be having difficulty was you. So you start to wonder: what is it about the packed room, the cacophony of voices all struggling to be heard, that throws hearing-impaired ears for a loop? It seems like hearing well in a crowd is the first thing to go, but what’s the reason? Scientists have begun to discover the answer, and it all starts with selective hearing.

How Does Selective Hearing Function?

The phrase “selective hearing” is a process that doesn’t even happen in the ears and is technically known as “hierarchical encoding”. This process nearly exclusively occurs in your brain. At least, that’s in accordance with a new study carried out by a team from Columbia University.

Ears work like a funnel as scientists have known for quite a while: they send all of the unprocessed data that they collect to your brain. In the auditory cortex the real work is then done. That’s the part of your gray matter that processes all those impulses, interpreting impressions of moving air into recognizable sounds.

Just what these processes look like was still unknown in spite of the established knowledge of the role played by the auditory cortex in the hearing process. Thanks to some innovative research methods including participants with epilepsy, scientists at Columbia were able to find out more about how the auditory cortex functions in relation to picking out voices in a crowd.

The Hierarchy of Hearing

And here’s what these intrepid scientists found: most of the work done by the auditory cortex to pick out particular voices is done by two separate regions. They’re what enables you to separate and intensify particular voices in loud situations.

  • Superior temporal gyrus (STG): At some point your brain will need to make some value based choices and this happens in the STG once it receives the voices that were previously separated by the HG. The superior temporal gyrus figures out which voices you want to focus on and which can be securely moved to the background.
  • Heschl’s gyrus (HG): The first sorting phase is handled by this part of the auditory cortex. Heschl’s gyrus or HG breaks down each individual voice and separates them into discrete identities.

When you have hearing problems, your ears are lacking specific wavelengths so it’s harder for your brain to recognize voices (depending on your hearing loss it could be low or high frequencies). Your brain isn’t supplied with enough data to assign separate identities to each voice. Consequently, it all blends together (meaning interactions will more difficult to understand).

New Science = New Algorithm

Hearing aids already have functions that make it easier to hear in noisy circumstances. But hearing aid makers can now incorporate more of those natural functions into their algorithms because they have a greater concept of what the process looks like. As an example, you will have a greater capacity to hear and comprehend what your coworkers are saying with hearing aids that help the Heshl’s gyrus and do a little more to separate voices.

Technology will get better at mimicking what happens in nature as we uncover more about how the brain works in combination with the ears. And that can result in improved hearing outcomes. That way, you can concentrate a little less on struggling to hear and a little more on enjoying yourself.

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