Man can't hear in a crowded restaurant.

Selective hearing is a term that commonly gets tossed about as a pejorative, an insult. Maybe you heard your mother suggest that your father had “selective hearing” when she suspected he might be ignoring her.

But actually selective hearing is quite the talent, an impressive linguistic accomplishment executed by teamwork between your ears and brain.

The Difficulty Of Trying to Hear in a Crowd

This situation potentially feels familiar: you’re feeling tired from a long workday but your friends all really would like to go out for dinner and drinks. They choose the loudest restaurant (because they have great food and live entertainment). And you spend an hour and a half straining your ears, trying to follow the conversation.

But it’s tough, and it’s taxing. This indicates that you might have hearing loss.

You think, maybe the restaurant was simply too noisy. But… everyone else appeared to be having a great time. The only one who appeared to be having difficulty was you. So you begin to wonder: what is it about the packed room, the cacophony of voices all battling 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 why? Scientists have begun to uncover the answer, and it all begins with selective hearing.

Selective Hearing – How Does it Work?

The scientific term for what we’re broadly calling selective hearing is “hierarchical encoding,” and it doesn’t happen inside of your ears at all. This process almost completely occurs in your brain. At least, that’s in accordance with a new study performed by a team at Columbia University.

Scientists have known for quite a while that human ears basically work as a funnel: they collect all the signals and then send the raw data to your brain. In the auditory cortex the real work is then accomplished. That’s the part of your gray matter that processes all those impulses, translating sensations of moving air into perceptible sounds.

Because of comprehensive research with CT and MRI scans, scientists have recognized for years that the auditory cortex plays a substantial role in hearing, but they were clueless with regards to what those processes really look like. Scientists were able, by using unique research techniques on people with epilepsy, to get a better understanding of how the auditory cortex picks out voices in a crowd.

The Hearing Hierarchy

And the insight they found out follows: the majority of the work accomplished by the auditory cortex to isolate distinct voices is done by two separate regions. They’re what enables you to separate and enhance distinct voices in loud situations.

  • Heschl’s gyrus (HG): This is the region of the auditory cortex that deals with the first phase of the sorting routine. Researchers observed that the Heschl’s gyrus (we’re just going to call it HG from now on) was breaking down each distinct voice, separating them into individual identities.
  • Superior temporal gyrus (STG): At some point your brain needs to make some value based decisions and this occurs in the STG after 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 confidently moved to the background.

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

New Science = New Algorithm

Hearing aids currently have features that make it less difficult to hear in loud environments. But hearing aid makers can now integrate more of those natural functions into their algorithms because they have a greater idea of what the process looks like. For example, hearing aids that do more to identify voices can help out the Heschl’s gyrus a little, leading to a better 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 conjunction with the ears, the better new technology will be capable of mimicking what happens in nature. And better hearing outcomes will be the result. That way, you can focus a little less on struggling to hear and a little more on enjoying yourself.

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