Evaluating the link between sound quality, speech recognition and cochlear implant-related quality of life outcomes

More than a million people around the world rely on cochlear implants (CIs) to hear. CI effectiveness is generally evaluated through speech recognition tests, and despite how widespread they are, CI sound quality is typically not considered an indicator of users' quality of life.

In JASA Express Letters, published on behalf of the Acoustical Society of America by AIP Publishing, researchers from Vanderbilt University Medical Center and Ohio State University evaluated the relationships between sound quality, speech recognition, and quality-of-life outcomes for CI users.

Hearing-related quality of life encompasses the impact of auditory abilities, communication, social participation, emotional well-being, and daily activities.

For someone with normal hearing, imagine trying to have a conversation while listening through an old radio, but you're not quite on the right channel frequency and there's poor reception."

Katelyn Berg, author

This is what the world sounds like with a poor-quality CI. A speaker's voice can seem robotic or tinny, and music lacks richness. This can be due to a variety of technological constraints in the CIs, like channel interactions between electrodes or other acoustic fidelity issues.

The researchers found CI sound quality leads to a 32% variance in users' quality of life - in contrast, speech recognition has virtually no predictive power over quality of life. In their study, speech recognition only correlated with sound quality under noisy conditions, suggesting it is particularly relevant in situations with background noise and different sound sources - in other words, the real world.

"This challenges decades of clinical practice focused primarily on using speech understanding in quiet as the primary metric for cochlear implant success," said Berg.

Forty-one CI users ranging in age from 18 to 80 participated in the study. They completed a set of computerized speech recognition tests, and answered two questionnaires - the Speech, Spatial and Qualities (SSQ) questionnaire, and the Cochlear Implant Quality of Life (CIQOL) questionnaire, both validated assessment tools within the audiological field. Part of the SSQ evaluates perceived sound quality, ability to segregate sounds, and listening effort. CIQOL measures quality of life across six domains: communication, emotional, entertainment, environment, listening effort, and social functioning.

The group plans to study the differences in quality of different types of sound, particularly speech and music, and to optimize how the device is programmed based on the placement of the electrode array. They emphasize the implications of this work on moving beyond quiet CI testing environments.

"While speech recognition testing remains important, incorporating sound quality measures could provide a more complete picture of cochlear implant outcomes and guide more targeted interventions for the challenging listening situations patients actually need to navigate in their daily lives," said Berg.