People with hearing loss can find the listening demands of daily life exhausting. For example, having a conversation with friends in a busy café where there is interfering background noise can be very challenging. Because of these challenges, people with hearing loss often need time to recover after work and can’t fully take part in social activities. We need to understand why listening can be such hard work, and how we can measure this 'listening effort'.
Currently, we don’t know what happens in someone’s brain when they listen in challenging environments through hearing aids. It’s difficult to measure brain activity in people using hearing aids, as widely-used methods like fMRI (functional magnetic resonance imaging) can’t be used with hearing aids. fNIRS (functional near-infrared spectroscopy) is a brain imaging method that can be used with hearing aids and can measure brain activity in people listening with them. fNIRS works by shining infrared light into the head to measure how much oxygen the brain is using. This shows how hard different parts of the brain are working; the more oxygen they are using, the harder they are working, and the more effort it’s taking to understand speech.
Ian’s main aim is to test a new way to measure what goes on in a person’s brain as they listen through hearing aids. Listening effort is commonly measured using pupillometry (measuring the size of someone’s pupils). Pupil size increases with increased listening effort, so if listening is more challenging, a person’s pupils will be larger. Ian will combine pupillometry with the new method, fNIRS, to study how brain activity relates to pupil size, and identify which parts of the brain work harder when people put more effort into listening. He will look at this in different amounts of background noise, and compare this to people without hearing loss.
Ian will also try to understand whether these lab-based measures of listening effort are a good reflection of the difficulties experienced by hearing aid users in their daily life. He will ask his volunteers to complete a questionnaire about how much effort they have to put in to listening, and look for links between their answers, the size of their pupils and their brain activity.
Combining different ways to measure listening effort will improve our understanding of this burden and how to best measure it in people with hearing loss. People with hearing loss need better hearing aids to help them to communicate more effectively in noisy environments, to ensure that they can take part fully in work and social activities, and to protect them from listening-related fatigue. New insights from this project could help hearing aid manufacturers to properly assess how hard it is for people to listen with their devices. This will help them to improve the design of their hearing aids, to make listening as easy as possible on the brain.