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Man can't hear in a crowded restaurant.

Sometimes when a person has a hard time hearing, someone close to them insultingly says they have “selective hearing”. When your mother used to accuse you of having “selective hearing,” she meant that you paid attention to the part about going to the fair and (perhaps intentionally) disregarded the part about doing your chores.

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

The Difficulty Of Trying to Hear in a Crowd

This situation potentially feels familiar: you’ve been through a long day at work, but your friends all insist on going out to dinner. They pick the noisiest restaurant (because it’s popular and the deep-fried cauliflower is delicious). And you spend an hour and a half straining your ears, trying to follow the conversation.

But it’s difficult, and it’s taxing. This indicates that you may have hearing loss.

Perhaps, you rationalize, the restaurant was simply too noisy. But… everyone else seemed to be having a fine go of it. The only person who appeared to be having trouble was you. Which gets you thinking: what is it about the packed room, the cacophony of voices all struggling to be heard, that causes hearing impaired ears to struggle? It seems like hearing well in a crowd is the first thing to go, but why? Scientists have begun to reveal 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 take place in your ears at all. Most of this process occurs in the brain. At least, that’s as reported by a new study performed by a team from Columbia University.

Ears work just like a funnel as scientists have known for some time: they forward all of the raw data that they collect 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 signals, interpreting sensations of moving air into perceptible sounds.

Precisely what these processes look like had remained a mystery in spite of the established knowledge of the role played by the auditory cortex in the hearing process. Scientists were able, by using novel research techniques on individuals with epilepsy, to get a better picture of how the auditory cortex discerns voices in a crowd.

The Hearing Hierarchy

And the information they discovered are as follows: most of the work done by the auditory cortex to isolate particular voices is done by two separate regions. They’re what enables you to sort and amplify distinct voices in noisy situations.

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

When you have hearing problems, your ears are lacking particular wavelengths so it’s more difficult for your brain to differentiate voices (high or low, depending on your hearing loss). Your brain can’t assign separate identities to each voice because it doesn’t have enough data. It all blends together as a consequence (which makes conversations tough to follow).

A New Algorithm From New Science

Hearing aids currently have functions that make it less difficult to hear in loud settings. But hearing aid manufacturers can now include more of those natural functions into their algorithms because they have a better idea of what the process looks like. As an example, hearing aids that do more to differentiate voices can help out the Heschl’s gyrus a little bit, bringing about a greater ability for you to understand what your coworkers are talking about in that noisy restaurant.

The more we understand about how the brain works, particularly in connection with the ears, the better new technology will be able to mimic what takes place in nature. And better hearing success will be the outcome. That way, you can concentrate a little less on straining to hear and a little more on enjoying yourself.