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Localization by Postlingually Deafened Adults Fitted With a Single Cochlear Implant
Author(s) -
Grantham D Wesley,
Ricketts Todd A.,
Ashmead Daniel H.,
Labadie Robert F.,
Haynes David S.
Publication year - 2008
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1097/mlg.0b013e31815661f9
Subject(s) - monaural , loudspeaker , cochlear implant , audiology , azimuth , binaural recording , anechoic chamber , horizontal plane , sound localization , noise (video) , acoustics , speech recognition , psychology , computer science , medicine , mathematics , physics , artificial intelligence , geometry , image (mathematics)
Objective: The main purpose of the study was to assess the ability of adults with unilateral cochlear implants to localize noise and speech signals in the horizontal plane. Design: Six unilaterally implanted adults, all postlingually deafened and all fitted with MED‐EL COMBI 40+ devices, were tested with a modified source identification task. Subjects were tested individually in an anechoic chamber, which contained an array of 43 numbered loudspeakers extending from –90° to +90° azimuth. On each trial, a 200 millisecond signal (either a noise burst or a speech sample) was presented from one of nine active loudspeakers, and the subject had to identify which source (from the 43 loudspeakers in the array) produced the signal. Results: The relationship between source azimuth and response azimuth was characterized in terms of the adjusted constant error ( Ĉ ). Ĉ for three subjects was near chance (50.5°), whereas Ĉ for the remaining three subjects was significantly better than chance (35°–44°). By comparison, Ĉ for a group of normal‐hearing listeners was 5.6°. For two of the three subjects who performed better than chance, monaural cues were determined to be the basis for their localization performance. Conclusions: Some unilaterally implanted subjects can localize sounds at a better than chance level, apparently because they can learn to make use of subtle monaural cues based on frequency‐dependent head‐shadow effects. However, their performance is significantly poorer than that reported in previous studies of bilaterally implanted subjects, who are able to take advantage of binaural cues.