# Binaural unmasking of tones and speech in bilateral cochlear implantees

> **NIH NIH R01** · UNIV OF MARYLAND, COLLEGE PARK · 2020 · $374,591

## Abstract

ABSTRACT: Binaural hearing can provide greatly improved signal detection and speech understanding in back-
ground noise. However, bilateral cochlear-implant (BICI) users demonstrate limited binaural unmasking (i.e.,
improved detection and understanding) of signals using speech processors. The gap in knowledge is that it is
unclear why binaural unmasking nearly disappears when using speech processors. Until the binaural benefit gap
is better understood and reduced, BICI users will have a relatively poor quality of life because of difficulty local-
izing sounds and communicating in background noise. The long-term goal is to understand and maximize bin-
aural benefits imparted by BICIs. The objective in this application is to understand the breakdown of binaural
unmasking as the stimulus complexity increases and when signals are presented via speech processors. The
central hypothesis is that BICI users' binaural unmasking is primarily stunted by the interaural decorrelation
caused by stimulus-encoding-driven factors (modulations, current spread, and compression). Most studies have
shown underwhelming binaural unmasking in BICI users, but few have considered the limiting role of interaural
decorrelation. Our approach to investigate this problem is two-pronged: to better understand and increase un-
masking in BICI listeners, and better understand and intentionally decrease unmasking in NH listeners (i.e.,
making them more like the BICI listeners). Then, we will compare perceptual performance to stimulus analyses
of the physical waveforms, the stimuli processed by speech processing algorithms, and modeled neural repre-
sentations of the electrical signals. With strong preliminary data in hand, the central hypothesis will be tested by
pursuing four specific aims: (1) Measure the extent to which the internal representation of modulated single-
electrode stimuli in BICI listeners is interaurally decorrelated; (2) Measure the extent to which current spread and
compression limit binaural unmasking of tones in noise in multi-electrode stimulation; (3) Develop a model of
across-frequency static and dynamic ILD processing; and (4) Measure the extent to which binaural unmasking
of speech in noise is reduced by interaural decorrelation from modulations, current spread, and compression.
The approach is innovative because it (1) investigates signal-based factors affecting binaural unmasking and
other binaural benefits in BICIs and (2) investigates the role of ILDs to impart these benefits. The proposed
research is significant because it helps us understand the barriers to larger binaural benefits in BICI users, which
can inform changes to speech processing strategies and clinical device setting guidelines. Larger binaural un-
masking and benefits will produce an important positive impact on CI users' quality of life because they will be
better able to localize sounds and communicate in noisy environments.

## Key facts

- **NIH application ID:** 9933869
- **Project number:** 5R01DC014948-05
- **Recipient organization:** UNIV OF MARYLAND, COLLEGE PARK
- **Principal Investigator:** Matthew J. Goupell
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $374,591
- **Award type:** 5
- **Project period:** 2016-06-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9933869

## Citation

> US National Institutes of Health, RePORTER application 9933869, Binaural unmasking of tones and speech in bilateral cochlear implantees (5R01DC014948-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9933869. Licensed CC0.

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