Hearing Health Blog

Man can't hear in a crowded restaurant.

Selective hearing is a term that normally is used as a pejorative, an insult. Perhaps you heard your mother accuse your father of having “selective hearing” when she suspected he was ignoring her.

But it turns out that selective hearing is quite the ability, an impressive linguistic feat carried out by cooperation between your brain and ears.

Hearing in a Crowd

This scenario probably seems familiar: you’re feeling burnt out from a long workday but your friends all really want to go out for dinner and drinks. They pick the loudest restaurant (because they have incredible food and live entertainment). And you strain and struggle to follow the conversation for the entire evening.

But it’s very difficult and exhausting. And it’s a sign of hearing loss.

You think, maybe the restaurant was simply too noisy. But no one else appeared to be struggling. The only person who appeared to be having trouble was you. Which gets you thinking: Why do ears that have hearing impairment have such a difficult time with the noise of a crowded room? Just why is it that being able to hear in a crowd is so quick to go? The solution, according to scientists, is selective hearing.

How Does Selective Hearing Function?

The scientific name for what we’re broadly calling selective hearing is “hierarchical encoding,” and it doesn’t take place inside of your ears at all. This process nearly exclusively occurs in your brain. At least, that’s as reported by a new study done by a team from Columbia University.

Scientists have known for quite some time that human ears effectively work like a funnel: they compile all the impulses and then deliver the raw information to your brain. In the auditory cortex the real work is then accomplished. That’s the part of your brain that handles all those signals, translating sensations of moving air into perceptible sounds.

Because of extensive research with MRI and CT scans, scientists have understood for years that the auditory cortex plays a crucial role in hearing, but they were stumped regarding what those processes actually look like. Scientists were able, by making use of novel research techniques on individuals with epilepsy, to get a better understanding of how the auditory cortex discerns voices in a crowd.

The Hearing Hierarchy

And here is what these intrepid scientists learned: the majority of the work performed by the auditory cortex to isolate distinct voices is done by two different parts. And in loud situations, they allow you to isolate and intensify certain voices.

  • Heschl’s gyrus (HG): This is the part of the auditory cortex that takes care of the first stage of the sorting process. Heschl’s gyrus or HG breaks down each unique voice and separates them into distinguishable identities.
  • Superior temporal gyrus (STG): Sooner or later your brain will need 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 determines which voices you want to focus on and which can be confidently moved to the background.

When you have hearing loss, your ears are missing certain wavelengths so it’s more difficult for your brain to differentiate voices (low or high, based upon your hearing loss). Your brain isn’t supplied with enough data to assign individual identities to each voice. It all blurs together as a result (which makes discussions difficult to follow).

A New Algorithm From New Science

Hearing aids already have functions that make it less difficult to hear in loud environments. But hearing aid manufacturers can now include more of those natural functions into their algorithms because they have a greater idea of what the process looks like. For instance, hearing aids that do more to distinguish voices can help out the Heschl’s gyrus a little bit, resulting in a greater ability for you to understand 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 lead to better hearing success. Then you can concentrate a little more on enjoying yourself and a little less on straining to hear.

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