title: Monaural Beamforming in Bimodal Cochlear Implant Users: Effect of (A)symmetric Directivity and Noise Type.
abstract: OBJECTIVE
  To evaluate monaural beamforming in bimodally aided cochlear implant (CI) users.
  
  
  METHODS
  The study enrolled twelve adult bimodal listeners with at least six months of CI-experience and using a contralateral hearing aid (HA) most of the daytime. Participants were uniformly fitted with the same CI speech processor and HA, giving access to an identical monaural beamformer in both ears. A within-subject repeated measures design evaluated three directional configurations [omnidirectional, asymmetric directivity (in CI alone) and symmetric directivity (in both CI and HA)] in two noise types [stationary and fluctuating]. Bimodal speech reception thresholds (SRT) as well as listening effort ratings were assessed in a diffuse noise field.
  
  
  RESULTS
  Symmetric monaural beamforming provided a significant SRT improvement of 2.6 dB SNR, compared to 1.6 dB SNR for asymmetric monaural beamforming. Directional benefits were similarly observed in stationary and fluctuating noise. Directivity did not contribute to less listening effort in addition to improvement in speech intelligibility. Bimodal performance was about 7 dB SNR worse in fluctuating than in stationary noise.
  
  
  CONCLUSIONS
  Monaural beamforming provided substantial benefit for speech intelligibility in noise for bimodal listeners. The greatest benefit occurred when monaural beamforming was activated symmetrically in both CI and HA. Monaural beamforming does not bridge the gap between bimodal and normal hearing performance, especially in fluctuating noise. Results advocate further bimodal co-operation.
  
  
  BACKGROUND
  This trial was registered in www.trialregister.nl under number NTR4901.
authors.affiliation: Department of ENT/Audiology, School for Mental Health and Neuroscience (MHENS), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Elke M J
authors.identifier: http://orcid.org/0000-0001-5017-316X
authors.initials: EM
authors.lastname: Devocht
authors.affiliation: Department of ENT/Audiology, School for Mental Health and Neuroscience (MHENS), Maastricht University Medical Center, Maastricht, The Netherlands.|Department of Methodology and Statistics, School for Public Health and Primary Care (CAPHRI), Maastricht University, Maastricht, The Netherlands.
authors.forename: A Miranda L
authors.initials: AM
authors.lastname: Janssen
authors.affiliation: Advanced Bionics European Research Centre, Hannover, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Chalupper
authors.affiliation: Department of ENT/Audiology, School for Mental Health and Neuroscience (MHENS), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Stokroos
authors.affiliation: Department of ENT/Audiology, School for Mental Health and Neuroscience (MHENS), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Erwin L J
authors.initials: EL
authors.lastname: George
mesh_terms: D000328:Adult; D000368:Aged; D001309:Auditory Threshold; D019929:Cochlear Implantation; D003054:Cochlear Implants; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise; D011474:Prosthesis Design; D013065:Speech Intelligibility; D013067:Speech Perception; D055815:Young Adult