Cochlear Implant Compression Optimization for Musical Sound Quality in MED-EL Users

Abstract

Objectives: Variations in loudness are a fundamental component of the music listening experience. Cochlear implant (CI) processing, including amplitude compression, and a degraded auditory system may further degrade these loudness cues and decrease the enjoyment of music listening. This study aimed to identify optimal CI sound processor compression settings to improve music sound quality for CI users.Design: Fourteen adult MED-EL CI recipients participated (Experiment No. 1: n = 17 ears; Experiment No. 2: n = 11 ears) in the study. A software application using a modified comparison category rating (CCR) test method allowed participants to compare and rate the sound quality of various CI compression settings while listening to 25 real-world music clips. The two compression settings studied were (1) Maplaw, which informs audibility and compression of soft level sounds, and (2) automatic gain control (AGC), which applies compression to loud sounds. For each experiment, one compression setting (Maplaw or AGC) was held at the default, while the other was varied according to the values available in the clinical CI programming software. Experiment No. 1 compared Maplaw settings of 500, 1000 (default), and 2000. Experiment No. 2 compared AGC settings of 2.5:1, 3:1 (default), and 3.5:1. Results:In Experiment No. 1, the group preferred a higher Maplaw setting of 2000 over the default Maplaw setting of 1000 (p = 0.003) for music listening. There was no significant difference in music sound quality between the Maplaw setting of 500 and the default setting (p = 0.278). In Experiment No. 2, a main effect of AGC setting was found; however, no significant difference in sound quality ratings for pairwise comparisons were found between the experimental settings and the default setting (2.5:1 versus 3:1 at p = 0.546; 3.5:1 versus 3:1 at p = 0.059).Conclusions: CI users reported improvements in music sound quality with higher than default Maplaw or AGC settings. Thus, participants preferred slightly higher compression for music listening, with results having clinical implications for improving music perception in CI users.

Optimization of Sound Coding Strategies to Make Singing Music More Accessible for Cochlear Implant Users

“…This result might have been caused by the strong compression applied to the music by the sound coding strategy and the much narrower EDR available for CI users in applied to recorded comparison to the perceivable DR in NH listeners. Gilbert et al (2022) showed that CI users prefer less compression (allocate more EDR) to the softer passages (below the knee point) and be more compressive for louder (above the knee point) parts of music with respect to the clinical compression system. Results of our study show the efficacy and importance of a back-end compression for music in the Crystalis sound coding strategy.…”

Listening to Music Through Hearing Aids: Potential Lessons for Cochlear Implants

“…There are very few systematic studies exploring the effect on music perception of varying the compression threshold or the compression ratio of the front-end AGC in a CI. Gilbert et al (2021) explored the effect of varying the compression ratio of the front-end AGC in the Med-El CI, keeping the compression threshold fixed at 48 dB SPL, and found no significant effect on music preferences. However, they varied the compression ratio only over a small range (2.5 to 3.5) and they used samples of music with a single fixed input level of 65 dBA.…”

Loudness Balancing Optimization for Better Speech Intelligibility, Music Perception, and Spectral Temporal Resolution in Cochlear Implant Users

“…Although speech understanding remains possible despite significant impairment in spectral and temporal cues, the same limitation can significantly affect CI users' ability to appreciate and recognize music, including melody and timbre (16,17). Although different sound processing strategies, current routing techniques, stimulation modes, and DR compression have been used in studies to optimize CI fitting for music and speech perception (18)(19)(20)(21), the effect of different CI programming methods has not been investigated. Therefore, the first aim of the study was to investigate the effect of two different programming methods on CI users' speech perception, spectral-temporal resolution, and music perception, the objective eSRT-based program and the behaviorally based program with LB.…”