Noise management for cochlear implants: Clinical state of the art and future perspectives

Cochlear implant (CI) users suffer particularly severe impairments when listening in noisy or otherwise adverse acoustic conditions. Modern CI speech processors are hence being equipped with a growing number of signal processing options for improved speech understanding and listening comfort in the face of environmental disturbances. Advanced Bionics’ most recent generation of speech processor, for example, features algorithms for the suppression stationary and impulsive noise, wind noise and reverberation as well as program automation and a binaural four-microphone beamformer utilizing a bidirectional wireless audio link between two processors.
In a recent study with 15 experienced bilateral CI users, the benefit of the binaural beamformer was evaluated and compared to a monaural beamformer acting independently on either side. Speech reception thresholds (SRTs) were measured using the Oldenburg sentence tests with speech being presented from 0° and uncorrelated, speech-shaped noise from 7 loudspeakers surrounding the listener. SRTs with the binaural beamformer improved by 1.5dB over the monaural beamformers and by 6.0dB over the omnidirectional processor microphone (t-Test, p < 0.001 each), highlighting the feasibility and usefulness of binaural noise reduction schemes for CIs.
Linked audio signals shared between two bilaterally-worn opens up a wide range of new approaches to binaural signal enhancement, arguably even more so than in acoustic hearing. Promising concepts under current investigation will be further discussed, considering both bilateral electric and bimodal (electric-acoustic) applications.