Advancements in Hearing Research and Audiological Rehabilitation

More men than women have a hearing loss, and the incidence of hearing loss increases with age. In a study from 2010, the Knowledge Center for Hearing Disabilities estimated that 800,000 Danes have disabling hearing loss. The population projection from Statistics Denmark (2018) shows that the Danish population is expected to grow, primarily due to a growth of the oldest portion of the population. This will result in more people in need of treatment for hearing loss in the future.

Clinical Measures and Hearing Aid Treatment

The hearing threshold is the clinical measure most often used to determine whether there is hearing loss and, if so, how severe. This is measured by tone audiometry which tests how intense a given tone must be presented before it can be heard by the patient. Hearing loss can also manifest in the form of difficulty understanding and distinguishing words from one another. This is typically measured by speech audiometry in which a number of words are played and must be repeated by the patient.

The most frequent treatment for hearing loss is the fitting of hearing aids. A hearing aid works by receiving and amplifying sound before sending the amplified sound signal to the ear. Described as such it may seem simple, yet both hearing and sound processing are complex tasks, and there still remains conditions that make successful hearing aid treatment a challenge to obtain across the hearing impaired population.

Technological Research: The ELLIIT Project and the Cocktail-Party Problem

To address these challenges, researchers are working on the ELLIIT project, “Brain-Based Monitoring of Sound”, which is a collaboration between Linköping University, Lund University, Oticon A/S and Eriksholm Research Centre. The focus of the project is making progress within modelling and signal processing for sound source separation, by investigating EEG responses to multi-speaker sound. Specifically, the project entails work towards solving auditory challenges in a “cocktail-party” scenario, were single speakers must be attended in an environment with multiple, similarly loud, speakers.

Developing noise-robust methods retaining a high spectral and temporal resolution for feature extraction is vital for a realistic application within EEG. Researchers will develop accurate models of the system from sound stimuli to locations of brain sources using EEG measurements. This will provide a better understanding for how the sound is processed at different stages in the brain for both normal-hearing and hearing-impaired listeners, opening up for future advanced hearing aid solutions.

Investigating Listening Effort via the EASYLI Project

Within the EASYLI project, researchers will investigate the physiological and subjective signatures of listening effort. The goal is to figure out how people evaluate which listening tasks to engage in, or in other words, what listening value they assign to a task depending on its difficulty and their motivation. Involving fNIRS and pupillometry in our research will shed light on the factors influencing listening effort and its associated brain activity. We hope that, ultimately, we can contribute to improving the overall listening experience for people with hearing impairments.

Clinical Insights from the BEAR Project

BEAR is a five-year project whose goal is to improve hearing aid treatment in Denmark based on clinical research, and if favourable, evidence-based renewal of clinical practice. In the first part of the BEAR project, a database containing information on almost 2,000 patients was established. Overall, it was found that hearing aid treatment significantly improved patients’ hearing-related quality of life.

Data Summary: Definitions of Asymmetrical Hearing Loss

Research within the project utilized specific clinical criteria to categorize patients. The following definitions were used for asymmetrical hearing loss:

• Pure-Tone Average (PTA): More than 15 dB interlateral difference over four frequencies.
• Word Recognition Score (WRS): More than 15% interlateral difference.
• Audiogram Configuration: Interlateral difference in configuration.

It was shown that no matter the definition of asymmetrical hearing loss, patients had poorer hearing-related quality of life and spatial hearing before treatment compared to patients with symmetric hearing loss. However, two months of hearing aid treatment improved both groups’ hearing-related quality of life and speech comprehension, regardless of asymmetry definition.