New evidence shows we are closing a gap to normal hearing. The collective results of recent studies involving normal-hearing and hearing-impaired adults demonstrate that it is possible for people with hearing loss to have active communication in the same noisy environments as their normal-hearing peers.

Eyes on Listening Effort

Speech understanding in noise is exhausting for people with hearing loss and becomes increasingly exhausting as the noise increases.

Even people with normal hearing expend more effort understanding speech as noise levels rise. In these situations, the brain works harder to make sense of sound.

A hearing aid with advanced signal processing, designed to support the hard work the brain does, can significantly lessen the mental effort required to understand speech in noise, preserving the mental resources needed to engage in social activities. 

Data derived from pupillometry, a useful and objective measurement of the pupil response, can be used to interpret the amount of listening effort as well as when giving up trying to process speech occurs.

When we pay attention to sound and ignore noise concurrently,  muscle activity in the iris changes the pupil size. Generally speaking, the more effort we apply in our listening process, the larger our pupils may get. Thus, when testing a listener in environments that go from very easy to very difficult conditions, the peak pupil dilation (PPD) will increase gradually until a certain point, from which point it will begin decreasing again. 

When It’s Not Worth the Effort

Listening effort typically depends on the interaction of two factors: how much effort the task demands, such as the listening in a noisy or quiet sound environment; and listener-related factors, such as an individual’s hearing status, e.g., normal hearing or hearing loss.

Another factor that enters the equation is motivation. People tend to conserve their resources, only investing resources in tasks where they believe the goal can be pursued successfully.

Earlier studies, using pupillometry, found that people with hearing loss give up trying to process speech in sound environments of around -1dB signal-to-noise ratio (SNR), even when wearing hearing aids.

Situations such as conversing in a restaurant have an SNR of -5dB or poorer. At this level of noise, listening becomes too difficult for many people with hearing loss. They give up and are no longer willing to invest the effort in following conversations. 

Normal Hearing as a Benchmark 

When we measure the benefits of hearing aids, normal hearing is the toughest benchmark.

A new study investigated speech understanding and listening effort in listeners with normal hearing for their age group, creating a unique opportunity to compare the study results to a similar study of people with hearing loss.
 

Purpose of the study:

• Examine the listening effort in normal hearing listeners in difficult acoustic environments / conditions
• Interpret the point of ‘giving up’ for trying to make sense of speech for this population
• Compare results with a similar study that used listeners with hearing loss who were wearing hearing aids

Participants:

• 24 adults with normal hearing for their age

Conditions:

• Speech in babble and steady-state noise
• Range of speech understanding from 0% - 100% in listening situations that simulated real-life environments - at home in quiet surroundings, noisy restaurants, and noisier conditions where speech understanding is impossible

The participants performed the Danish Hearing in Noise Test (HINT) in which everyday sentences are presented in babble and steady-state noise.  Researchers measured speech understanding and pupil response, giving the outcome measures of word recognition in percent and peak pupil dilation.

The study found that normal hearing listeners expended the most effort at approximately 60%-word recognition score (-4dB SNR) and suggested that listeners started to give up making an effort at around -8dB SNR.

The study results were compared to a study that used similar methodology but hearing-impaired participants.

In comparison study, the participants wore hearing aids with advanced technology that precisely analyses all sounds in the environment, with the capacity to scan and update more than 100 times per second and even remove noise between words.

The collective evidence shows that the point of giving up for people with hearing loss using hearing aids with this type of advanced technology occurred at the same point of giving up as people with normal hearing. 

Closing a Gap to Normal Hearing

The studies demonstrate that a hearing aid designed to support the work the brain does can make active communication possible in challenging environments and empower people with hearing loss to participate in the same social situations as their normal hearing peers.

This is an important conclusion and a point that we can use to encourage people with hearing loss to explore difficult listening situations where they may have given up in the past, such as social gatherings or noisy restaurants. 

By making active communication possible in challenging environments, advanced technology hearing aids can help people with hearing loss get the social stimulation they need to keep the brain fit as they age, potentially reducing the risk of cognitive decline.

References:
Juul Jensen 2018, Oticon Whitepaper

Read more about the study in the Whitepaper: "Closing a gap to normal hearing"