title: Vowel identification by listeners with hearing impairment in response to variation in formant frequencies.
abstract: OBJECTIVE
  This study examined the influence of presentation level and mild-to-moderate hearing loss on the identification of a set of vowel tokens systematically varying in the frequency locations of their second and third formants.
  
  
  METHODS
  Five listeners with normal hearing (NH listeners) and five listeners with hearing impairment (HI listeners) identified synthesized vowels that represented both highly identifiable and ambiguous examples of /i/, /[Please see symbol]/, and /[Please see symbol]/.
  
  
  RESULTS
  Response patterns of NH listeners showed significant changes, with an increase in presentation level from 75 dB SPL to 95 dB SPL, including increased category overlap. HI listeners, listening only at the higher level, showed greater category overlap than normal and overall identification patterns that differed significantly from those of NH listeners. Excitation patterns based on estimates of auditory filters suggested smoothing of the internal representations, resulting in impaired formant resolution.
  
  
  CONCLUSIONS
  Both increased presentation level for NH listeners and the presence of hearing loss produced a significant change in vowel identification for this stimulus set. Major differences were observed between NH listeners and HI listeners in vowel category overlap and in the sharpness of boundaries between vowel tokens. It is likely that these findings reflect imprecise internal spectral representations due to reduced frequency selectivity.
authors.affiliation: National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR, USA. michelle.molis@va.gov
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Molis
authors.forename: Marjorie R
authors.initials: MR
authors.lastname: Leek
mesh_terms: D000158:Acoustic Impedance Tests; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001307:Auditory Perception; D001309:Auditory Threshold; D016022:Case-Control Studies; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010700:Phonetics; D011571:Psychoacoustics; D012016:Reference Values; D013018:Sound Spectrography; D013067:Speech Perception