title: Effect of maximum power output and noise reduction on speech recognition in noise.
abstract: BACKGROUND
  The maximum power output (MPO) of a hearing aid was typically discussed in the context of avoiding loudness discomfort. However, an MPO that is too low, as in the cases to avoid discomfort for people with a severe loudness tolerance problem and hearing losses that exceed the fitting range of the hearing aids, could negatively affect sound quality and speech intelligibility in noise.
  
  
  OBJECTIVE
  The current study was designed to demonstrate the degradation in speech intelligibility in noise on the HINT (Hearing in Noise Test) when the MPO of the wearers' hearing aids was lowered by 10 dB from the default. The interactions with noise reduction (NR) algorithms (classic [NR-classic] and Speech Enhancer [NR-SE]) were also examined.
  
  
  METHODS
  A single-blinded, factorial repeated-measures design was used to study the effect of noise input level (68 dBC, 75 dBC), MPO setting (default and default-10), and NR algorithm (off, classic, SE) on HINT performance.
  
  
  METHODS
  Eleven adults with a severe sensorineural hearing loss participated.
  
  
  METHODS
  Participants were fit with the Widex m4-19 behind-the-ear hearing aids binaurally in the default frequency response and MPO settings. The hearing aids were adjusted to six MPO (default, default-10) by NR (off, classic, SE conditions). Testing was completed within one 2 hr session.
  
  
  METHODS
  The RTS (reception threshold for speech) for 50% correct on the HINT was measured in each of the six hearing aid conditions at two input levels (68 and 75 dBC) with speech and noise stimuli presented from the front. Repeated-measures ANOVAs were conducted using SPSS software to examine significant differences.
  
  
  RESULTS
  A repeated-measures ANOVA showed that noise level was not significant while NR algorithm and MPO were significant. The interaction between noise level and NR algorithm was also significant. Post hoc analysis with Bonferroni adjustment for the effect of NR algorithm showed that performance with NR-off was significantly poorer than performance with NR-classic and NR-SE (p < 0.05). However, NR-classic and NR-SE were not significantly different from each other (p > 0.05).
  
  
  CONCLUSIONS
  An MPO that was 10 dB lower than the default could negatively affect the signal-to-noise ratio (SNR) of the listening environment. However, NR could compensate for the degradation in SNR.
authors.affiliation: Office of Research in Clinical Amplification, Widex USA. fkuk@widexusa.com
authors.forename: Francis
authors.initials: F
authors.lastname: Kuk
authors.forename: Heidi
authors.initials: H
authors.lastname: Peeters
authors.forename: Chi
authors.initials: C
authors.lastname: Lau
authors.forename: Petri
authors.initials: P
authors.lastname: Korhonen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001309:Auditory Threshold / Q000502:physiology; D006310:Hearing Aids; D006319:Hearing Loss, Sensorineural / Q000628:therapy*; D006801:Humans; D008875:Middle Aged; D009622:Noise / Q000517:prevention & control*; D016037:Single-Blind Method; D013063:Speech Discrimination Tests; D013067:Speech Perception / Q000502:physiology*