title: Modulation-based digital noise reduction for application to hearing protectors to reduce noise and maintain intelligibility.
abstract: OBJECTIVE
  The objective of this study was to test the effects of modulation-based digital noise reduction (MB-DNR) on noise levels, speech intelligibility, and listening preference in four real-world noises.
  
  
  BACKGROUND
  A significant challenge in hearing protection device (HPD) design is to reduce ambient noise levels while maintaining users' ability to understand speech. MB-DNR technology, currently employed in hearing aids, potentially could be used to achieve these objectives.
  
  
  METHODS
  Speech and noise calibrated to signal-to-noise ratios (SNRs) of 0, -5, and -10 dB in the sound field were recorded at the outputs of two digital hearing aids in the ears of a Knowles Electronic Manikin for Acoustic Research with and without MB-DNR activated (i.e., NR and noNR, respectively). Listeners' speech intelligibility scores and sound quality preferences were evaluated while they listened to the recordings presented via ER-3A insert earphones at 85 dB SPL.
  
  
  RESULTS
  MB-DNR reduced the overall noise level by approximately 4 to 7 dB. Listeners obtained significantly higher speech intelligibility scores in the NR condition at an SNR of -10 dB in two noises and similar scores in the noNR and NR conditions in all other cases. They preferred the NR condition in all cases.
  
  
  CONCLUSIONS
  MB-DNR reduced overall noise level, enhanced sound quality, and maintained or improved speech intelligibility in the four military noises tested.
  
  
  CONCLUSIONS
  MB-DNR algorithms potentially could be incorporated into HPDs to enhance performance and increase user acceptance.
authors.affiliation: Department of Allied Health and Communicative Disorders, Northern Illinois University, 323 Wirtz Hall, DeKalb, IL 60115, USA. kchung@niu.edu
authors.forename: King
authors.initials: K
authors.lastname: Chung
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tufts
authors.forename: Lance
authors.initials: L
authors.lastname: Nelson
mesh_terms: D004430:Ear Protective Devices / Q000592:standards*; D006801:Humans; D009622:Noise / Q000517:prevention & control*; D012815:Signal Processing, Computer-Assisted; D013065:Speech Intelligibility