CI Atlas · Hearing Music Through an Implant · Module 12

12Rescuing the Melody: Bimodal and Electric-Acoustic Hearing

If one change could most improve how music sounds through an implant, it is adding back real acoustic hearing. Whether it comes from a hearing aid in the opposite ear (bimodal) or from low-frequency hearing preserved in the implanted ear (electric-acoustic stimulation, or hybrid), acoustic low-frequency hearing delivers the fine temporal structure and resolved low harmonics that carry pitch and melody. This module explains why bimodal and EAS listeners outperform electric-only listeners for melody, timbre and enjoyment, and what it means for hearing preservation and fitting.

FWhat acoustic low-frequency hearing adds back

The implant's channels deliver mainly slow envelope cues; they discard the fine temporal structure and the resolved low-numbered harmonics that the ear normally uses for pitch. Residual acoustic hearing in the low frequencies preserves temporal fine structure and resolves the lowest harmonics, the cues that most strongly carry melodic pitch. Bimodal hearing combines an implant in one ear with a contralateral hearing aid; electric-acoustic stimulation (EAS/hybrid) preserves acoustic low-frequency hearing in the implanted ear itself. In both, low-frequency acoustic information is layered onto the implant's mid-to-high electric channels, restoring the part of music the implant cannot encode.[2005][2006][2009]

The implant codes the high-frequency envelope and rhythm well but smears pitch, so recognising a familiar tune from melody alone sits near 39% with the electrode array on its own. Adding a contralateral hearing aid (bimodal) supplies some low-frequency fundamental and lifts scores into the mid-50s. Preserved same-ear low-frequency hearing through electric-acoustic stimulation restores resolved low harmonics and temporal fine structure, pushing melody recognition to roughly 68–74%. Illustrative.

TThe melody advantage in the data

Combining acoustic and electric hearing markedly improves melody recognition over the implant alone, with the acoustic ear carrying the pitch. In hybrid/EAS simulations, melody recognition was far higher with electric-acoustic (~68%) and acoustic (~74%) listening than with electric-alone (~39%). Bimodal music perception improves as more low-frequency acoustic bandwidth is made audible, with wideband contralateral amplification most beneficial for music quality. Acoustic-hearing users (HA) outperform CI-alone users on pitch and melody, reinforcing that the limiting factor is the electric pitch code, not the listener.[2005][2019][2021][2008]

An electrode array delivers a coarse envelope across mid- and high-frequency channels — enough for rhythm, timbre and consonants, but the channels are too broad to resolve individual harmonics, so pitch is smeared. Preserved acoustic hearing below about 750 Hz changes that: the healthy low-frequency cochlea resolves the first few harmonics of the voice or instrument fundamental (F0) and preserves temporal fine structure. Those resolved low harmonics are exactly the cues a melody is built from, so adding the acoustic ear rescues the pitch the implant cannot supply. Schematic.

CTimbre, enjoyment and a more natural sound

Low-frequency acoustic hearing restores the warmth and harmonic richness that make instruments and voices identifiable, improving timbre perception. Bimodal and EAS listeners commonly report that music and voices sound more natural and more enjoyable than with the implant alone. Timbre remains imperfect even with acoustic hearing, but the gain over electric-only is consistent and clinically meaningful for enjoyment. Better music perception and enjoyment is one of the strongest patient-reported reasons to preserve or supplement acoustic hearing.[2019][2021][2005]

Music benefit climbs steadily with the audible low-frequency bandwidth a surgeon manages to preserve. The first useful gains arrive early: hearing up to about 250 Hz already captures the fundamental of most voices and instruments. Widening the preserved band toward 500 Hz and beyond adds the lower resolved harmonics, so the curve keeps rising before it gradually saturates. This is the audiological case for soft-surgery, hearing-preservation electrodes: every preserved octave at the bottom is worth protecting. Illustrative.

CThe case for hearing preservation and fitting

Music outcomes make a strong case for hearing-preservation surgery (atraumatic technique, soft-surgery, appropriate array choice) to retain low-frequency acoustic hearing in the implanted ear. When acoustic hearing cannot be preserved, fitting a contralateral hearing aid (bimodal) recovers much of the same benefit. Fitting should maximise usable low-frequency acoustic bandwidth and balance loudness and pitch across the acoustic and electric components. Across-ear or electric-acoustic pitch mismatch should be considered when fitting, since misaligned pitch between ears can blunt the binaural and bimodal music benefit.[2006][2021][2014][2020]

Case 29.12 · Rescuing the Melody

A 45-year-old woman with a unilateral implant has excellent speech understanding but finds music 'flat and metallic.' She has aidable low-frequency hearing in her non-implanted ear but currently wears no hearing aid on that side.

Which intervention is most likely to improve her music perception?

Self-assessment — Module 123 questions

Question 1

Why does acoustic low-frequency hearing help music more than the implant's electric channels?

Question 2

Compared with electric-only listening, electric-acoustic (hybrid) listening primarily improves:

Question 3

Which patient is best positioned for the largest music benefit from acoustic hearing?

Tracked locally in your browser — see /progress for the dashboard.