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Man can't hear in a crowded restaurant.

Sometimes when a person has a hard time hearing, somebody close to them insultingly suggests they have “selective hearing”. When your mother used to accuse you of having “selective hearing,” she was suggesting that you listened to the part about chocolate cake for dessert and (perhaps purposely) ignored the bit about doing your chores.

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

The Stress Of Trying to Hear in a Crowd

Perhaps you’ve experienced this situation before: you’re feeling tired from a long day at work but your friends all really would like to go out for dinner and drinks. And naturally, they want to go to the noisiest restaurant (because it’s trendy and the deep-fried cauliflower is delicious). And you spend the entire evening straining your ears, trying to follow the conversation.

But it’s very difficult and exhausting. This suggests that you may have 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 wonder: what is it about the packed room, the cacophony of voices all battling to be heard, that causes hearing impaired ears to struggle? Just why is it that being able to hear in a crowd is so quick to go? The answer, 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 in your ears at all. This process almost exclusively happens in your brain. At least, that’s in line with a new study performed by a team at Columbia University.

Ears work just like a funnel as scientists have understood for some time: they collect all the impulses and then forward the raw information to your brain. In the auditory cortex the real work is then accomplished. That’s the part of your brain that processes all those impulses, translating sensations of moving air into recognizable sounds.

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

The Hierarchy of Hearing

And the facts they found follows: most of the work accomplished by the auditory cortex to isolate distinct voices is accomplished by two different regions. They’re what allows you to sort and intensify distinct voices in noisy environments.

  • Heschl’s gyrus (HG): The first sorting phase is taken care of by this region of the auditory cortex. Heschl’s gyrus or HG breaks down each unique voice and separates them into discrete identities.
  • Superior temporal gyrus (STG): Sooner or later your brain will need to make some value based decisions and this is done in the STG after it receives the voices which were previously differentiated by the HG. Which voices can be freely moved to the background and which ones you want to pay attention to is figured out by the STG..

When you start to suffer with hearing problems, it’s harder for your brain to identify voices because your ears are lacking particular wavelengths of sound (high or low, based upon your hearing loss). Your brain isn’t provided with enough information to assign individual identities to each voice. It all blurs together as a result (which makes conversations tough to follow).

New Science = New Algorithm

Hearing aids already have functions that make it less difficult to hear in loud settings. But now that we understand what the fundamental process looks like, hearing aid manufacturers can integrate more of those natural operations into their instrument algorithms. For instance, you will have a greater 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 distinguish voices.

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

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