Hearing Health Blog

Man can't hear in a crowded restaurant.

Selective hearing is a term that normally gets tossed about as a pejorative, an insult. When your mother used to accuse you of having “selective hearing,” she meant that you listened to the part about chocolate cake for dessert and (perhaps purposely) disregarded the bit about cleaning your room.

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

The Stress Of Trying to Hear in a Crowd

This scenario probably seems familiar: you’ve been through a long day at work, but your buddies all insist on going out to dinner. They pick the noisiest restaurant (because they have amazing 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. And it’s a sign of hearing loss.

Maybe, you rationalize, the restaurant was just too loud. But… everyone else seemed to be having a great time. The only person who appeared to be having difficulty was you. So you start to ask yourself: Why do ears that have hearing impairment have such a hard time with the noise of a packed room? It seems like hearing well in a crowd is the first thing to go, but why? The solution, as reported by scientists, is selective hearing.

Selective Hearing – How Does it Work?

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

Scientists have recognized for some time that human ears essentially work as a funnel: they forward all of the unprocessed data that they gather to your brain. That’s where the real work occurs, specifically the auditory cortex. That’s the part of your gray matter that processes all those signals, translating sensations of moving air into recognizable sounds.

Because of extensive research with CT and MRI scans, scientists have understood for years that the auditory cortex plays a crucial role in hearing, but they were clueless regarding what those processes actually look like. Thanks to some novel research techniques concerning participants with epilepsy, scientists at Columbia were able to find out more about how the auditory cortex functions when it comes to discerning voices in a crowd.

The Hierarchy of Hearing

And here is what these intrepid scientists found: there are two regions of the auditory cortex that manage most of the work in helping you identify specific voices. And in loud situations, they allow you to separate and enhance particular voices.

  • Superior temporal gyrus (STG): The separated voices go from the HG to the STG, and it’s here that your brain begins to make some value distinctions. Which voices can be safely moved to the background and which ones you want to focused on is determined by the STG..
  • Heschl’s gyrus (HG): The first sorting stage is managed by this part of the auditory cortex. Scientists observed that the Heschl’s gyrus (we’re just going to call it HG from now on) was processing each unique voice, classifying them into individual identities.

When you have hearing impairment, your ears are missing particular wavelengths so it’s harder for your brain to distinguish voices (depending on your hearing loss it might be low or high frequencies). Your brain isn’t furnished with enough data to assign separate identities to each voice. It all blurs together as a consequence (meaning interactions will more difficult to follow).

New Science = New Algorithm

It’s typical for hearing aids to have features that make it easier to hear in a crowd. But hearing aid manufacturers can now integrate more of those natural functions into their algorithms because they have a better concept of what the process looks like. For instance, hearing aids that do more to identify voices can help out the Heschl’s gyrus a little, bringing about a greater capacity for you to comprehend what your coworkers are saying in that noisy restaurant.

Technology will get better at mimicking what occurs in nature as we discover more about how the brain really works in conjunction with the ears. And that can result in better hearing outcomes. Then you can concentrate a little more on enjoying yourself and a little less on straining to hear.

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