Sometimes when a person has a difficult 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 chocolate cake for dessert and (maybe deliberately) ignored the bit about cleaning your room.
But in reality it takes an incredible act of teamwork between your ears and your brain to have selective hearing.
The Difficulty Of Trying to Hear in a Crowd
Maybe you’ve dealt with this situation before: you’re feeling burnt out from a long workday but your friends all really want to go out for dinner and drinks. They choose 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 suggests that you might have hearing loss.
You think, maybe the restaurant was simply too loud. But no one else seemed to be having difficulties. The only one who appeared to be having difficulty was you. Which gets you thinking: what is it about the crowded room, the cacophony of voices all trying 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 quick to go? Scientists have begun to reveal the answer, and it all begins with selective hearing.
How Does Selective Hearing Function?
The phrase “selective hearing” is a process that doesn’t even occur in the ears and is scientifically known as “hierarchical encoding”. Most of this process occurs in the brain. At least, that’s in accordance with a new study performed by a team from Columbia University.
Ears work like a funnel as scientists have known for some time: they send all of the raw data that they gather 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, translating sensations of moving air into perceptible sounds.
Just what these processes look like was still unknown despite the established knowledge of the role played by the auditory cortex in the process of hearing. Scientists were able, by making use of novel research techniques on people with epilepsy, to get a better picture of how the auditory cortex discerns voices in a crowd.
The Hearing Hierarchy
And here is what these intrepid scientists found: there are two components of the auditory cortex that perform most of the work in helping you identify particular voices. And in noisy settings, they enable you to isolate and amplify particular voices.
- Superior temporal gyrus (STG): Eventually your brain needs to make some value based decisions and this happens in the STG after it receives the voices that were previously differentiated by the HG. The superior temporal gyrus figures out which voices you want to pay attention to and which can be confidently moved to the background.
- Heschl’s gyrus (HG): This is the region of the auditory cortex that takes care of the first stage of the sorting routine. Heschl’s gyrus or HG breaks down each unique voice and separates them into discrete identities.
When you begin to suffer with hearing damage, it’s more difficult for your brain to differentiate voices because your ears are lacking certain wavelengths of sound (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 blurs together as a consequence (which makes interactions difficult to follow).
New Science = New Algorithm
It’s typical for hearing aids to come with features that make it easier to hear in a crowd. But now that we understand what the fundamental process looks like, hearing aid companies can incorporate more of those natural functions into their device algorithms. As an example, you will have a greater ability to hear and understand what your coworkers are talking about with hearing aids that help the Heshl’s gyrus and do a little more to identify voices.
The more we learn about how the brain works, particularly in combination with the ears, the better new technology will be able to mimic what takes place in nature. And better hearing outcomes will be the outcome. Then you can concentrate a little more on enjoying yourself and a little less on straining to hear.
