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Hearing Aids by Tricia Leagjeld - Redmond, OR

Man can't hear in a crowded restaurant.

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

But actually selective hearing is quite the talent, an amazing linguistic feat performed by cooperation between your brain and ears.

Hearing in a Crowd

This situation potentially feels familiar: you’ve been through a long day at work, but your buddies all insist on meeting up for dinner. And naturally, they want to go to the loudest restaurant (because it’s popular and the deep-fried cauliflower is the best in town). And you spend an hour and a half straining your ears, working hard to follow the conversation.

But it’s difficult, and it’s taxing. This suggests that you may have hearing loss.

You think, perhaps the restaurant was just too loud. But… everyone else seemed to be having a great time. The only person who appeared to be having trouble was you. So you begin to ask yourself: Why do ears that have hearing impairment have such a difficult time with the noise of a crowded room? It seems as if hearing well in a crowd is the first thing to go, but what’s the reason? The answer, according to scientists, is selective hearing.

How Does Selective Hearing Function?

The phrase “selective hearing” is a process that doesn’t even occur in the ears and is formally called “hierarchical encoding”. The majority of this process occurs in the brain. At least, that’s as reported by a new study done by a team from Columbia University.

Ears work just like a funnel which scientists have known for some time: they collect all the signals and then deliver the raw data to your brain. That’s where the heavy lifting takes place, particularly the auditory cortex. That’s the part of your brain that processes all those impulses, interpreting sensations of moving air into recognizable sounds.

Precisely what these processes look like had remained a mystery despite the established understanding of the role played by the auditory cortex in the process of hearing. Thanks to some innovative research techniques including participants with epilepsy, scientists at Columbia were able to discover more about how the auditory cortex works in relation to picking out voices in a crowd.

The Hearing Hierarchy

And here is what these intrepid scientists found: the majority of the work done by the auditory cortex to pick out distinct voices is done by two separate regions. And in loud environments, they enable you to isolate and boost specific voices.

  • Superior temporal gyrus (STG): Eventually your brain needs 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 pay attention to and which can be confidently moved to the background.
  • Heschl’s gyrus (HG): The first sorting phase is managed by this region of the auditory cortex. Scientists observed that the Heschl’s gyrus (we’re simply going to call it HG from here on out) was breaking down each unique voice, classifying them into individual identities.

When you have hearing impairment, your ears are lacking particular wavelengths so it’s harder for your brain to recognize voices (high or low, depending on your hearing loss). Your brain isn’t given enough data to assign individual identities to each voice. It all blurs together as a result (which makes interactions hard to follow).

New Science = New Algorithm

It’s common for hearing aids to have functions that make it less difficult to hear in a crowd. 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, hearing aids that do more to identify voices can help out the Heschl’s gyrus a little bit, resulting in a greater capacity for you to understand what your coworkers are talking about in that loud restaurant.

The more we discover about how the brain works, particularly in combination with the ears, the better new technology will be able to mimic what takes place in nature. And that can result in better hearing outcomes. Then you can focus a little more on enjoying yourself and a little less on straining to hear.