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Man can't hear in a crowded restaurant.

Selective hearing is a term that frequently gets tossed about as a pejorative, an insult. Perhaps you heard your mother accuse your father of having “selective hearing” when she thought he was ignoring her.

But actually it takes an amazing act of teamwork between your brain and your ears to have selective hearing.

The Difficulty Of Trying to Hear in a Crowd

This situation probably feels familiar: you’re feeling tired from a long day at work but your friends all really want to go out for dinner and drinks. They decide on 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 very difficult and exhausting. This indicates that you might have hearing loss.

You think, maybe the restaurant was just too noisy. But… everyone else appeared to be having a great time. You seemed like the only one experiencing trouble. Which gets you thinking: what is it about the packed room, the cacophony of voices all struggling to be heard, that throws hearing-impaired ears for a loop? Just why is it that being able to hear in a crowd is so challenging? The solution, according to scientists, is selective hearing.

How Does Selective Hearing Operate?

The scientific term for what we’re broadly calling selective hearing is “hierarchical encoding,” and it doesn’t take place inside of your ears at all. The majority of this process occurs in the brain. At least, that’s according to a new study performed by a team from Columbia University.

Ears work like a funnel which scientists have recognized for some time: they compile all the impulses and then send the raw information to your brain. In the auditory cortex the real work is then done. That’s the part of your brain that handles all those signals, interpreting sensations of moving air into perceptible 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. Scientists were able, by utilizing novel research techniques on individuals with epilepsy, to get a better picture of how the auditory cortex discerns voices in a crowd.

The Hierarchy of Hearing

And here’s what these intrepid scientists discovered: there are two parts of the auditory cortex that do most of the work in helping you key in on individual voices. And in noisy settings, they allow you to isolate and amplify certain voices.

  • Superior temporal gyrus (STG): The separated voices go from the HG to the STG, and it’s at this point that your brain starts to make some value determinations. The superior temporal gyrus figures out which voices you want to give attention to 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 loss, your ears are lacking particular wavelengths so it’s harder for your brain to recognize voices (depending on your hearing loss it might be low or high frequencies). Your brain can’t assign separate identities to each voice because it doesn’t have enough information. As a result, it all blends together (which makes conversations difficult to follow).

New Science = New Algorithm

Hearing aids currently have functions that make it easier to hear in loud circumstances. But now that we understand what the basic process looks like, hearing aid manufacturers can integrate more of those natural operations into their device algorithms. For example, you will have a better ability to hear and understand what your coworkers are saying with hearing aids that assist the Heshl’s gyrus and do a little more to identify voices.

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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