Hearing loss: why turning up the volume is not enough

Listening to a conversation at a cocktail party is a real challenge for the auditory system. Without realising it, we have to pick out the sound of a single voice from a complex mix of sounds in order to understand and follow it.

Researchers at Queen's University, led by Dr Ingrid Johnsrude, are studying how our brains meet this challenge and allow us to make out particular voices in crowded, noisy and distracting places. Her studies have shown that the brain does not rely only on the incoming sounds that reach the ear to understand and remember speech. It also draws on information from the other senses and on prior knowledge to help us understand.

These findings were presented at the 8th annual meeting of the Canadian Association for Neuroscience, held in Montreal, Canada, from 25 to 28 May 2014.

In Dr Johnsrude's studies, participants heard degraded or clear speech, with or without distraction. By looking at how different regions of the brain were activated while participants were exposed to different listening conditions, Dr Johnsrude's research showed that the early processing of sound, which takes place in a region of the brain called the primary auditory cortex, depends on higher-level language skills that are encoded in other regions of the brain.

Following a conversation in a noisy place means ignoring the surrounding noise and distractions and concentrating on the person you are talking to. Clear speech was understood and remembered whether or not participants were distracted by other tasks, but attention turned out to be critical for understanding degraded speech.

What you hear and understand in a conversation is shaped by what you are used to hearing, so a familiar voice will be easier to understand than a stranger's. This proved especially true for older adults: as they aged, they found it harder to understand new voices at a cocktail party, but showed no loss of ability to understand familiar voices in the same situation.

“The downside of ageing is well known. As you get older, everything gets worse,” says Dr Johnsrude. “You need glasses, your memory goes, and it is harder to hear when you are talking in a busy place like a restaurant or a party, where lots of people are speaking at once. I found the upside of ageing, and it is experience.” Older people's experience, such as how familiar they are with the voice of someone close to them, helps them make up for age-related decline.

Dr Johnsrude was also able to show that the activation of certain regions of the brain, the higher-order speech-sensitive cortex, could be seen as a neural signature of attentive listening. Measuring the effort needed to understand speech, using the techniques Dr Johnsrude developed, could offer a new way of assessing how effective and comfortable hearing aids are, and help researchers get the most out of these devices.

Canadian Association for Neuroscience. "Cocktail party neuroscience: Making sense of voices in a crowd." ScienceDaily, 28 May 2014. www.sciencedaily.com/releases/2014/05/140528133211.htm

In the light of this study, we can better understand that hearing is not just a question of volume, but also of attention, effort and higher-level language skills. These last three can be greatly improved with a listening programme using the Tomatis method.

That is why we recommend the method to anyone with hearing loss, at any age. On this subject, we invite you to read Thérèse's testimonial.