An Influence of Binaural Hearing Aids on Positioning of Sound Images An influence of binaural hearing aids on positioning of sound images produced by signals from two loudspeakers was investigated with normally hearing and hearing-impaired subjects. The image can be positioned along a horizontal line connecting the centers of the sources by adjusting the relative sound pressure levels of signals. When ... Research Article
Research Article  |   September 01, 1980
An Influence of Binaural Hearing Aids on Positioning of Sound Images
 
Author Affiliations & Notes
  • Anna K. Nábělek
    University of Tennessee, Knoxville
  • Tomasz Łętowski
    University of Tennessee, Knoxville
  • David Mason
    University of Tennessee, Knoxville
Article Information
Research Articles
Research Article   |   September 01, 1980
An Influence of Binaural Hearing Aids on Positioning of Sound Images
Journal of Speech, Language, and Hearing Research, September 1980, Vol. 23, 670-687. doi:10.1044/jshr.2303.670
History: Received July 10, 1978 , Accepted June 19, 1979
 
Journal of Speech, Language, and Hearing Research, September 1980, Vol. 23, 670-687. doi:10.1044/jshr.2303.670
History: Received July 10, 1978; Accepted June 19, 1979

An influence of binaural hearing aids on positioning of sound images produced by signals from two loudspeakers was investigated with normally hearing and hearing-impaired subjects. The image can be positioned along a horizontal line connecting the centers of the sources by adjusting the relative sound pressure levels of signals. When the listener is a symmetrical receiver, the image appears on the midline (0° azimuth) for equal levels or away from the midline for unequal levels. Any asymmetry of the receiver causes a shift of the image away from the midline. In the study, the level differences, ΓLs, necessary to position sound images at 0 and ± 12° azimuths were measured. The baseline data were collected for 10 normally hearing subjects in unaided and aided conditions. In the aided conditions binaural aids were balanced (equal gains) or unbalanced (10 dB disparity in gains). The normally hearing subjects positioned the image on the midline with a group mean ΓLs of 0 dB.in both unaided and balanced aided conditions. To position the image at +12 or -12° azimuth they needed mean ΓLs that could be predicted from a theoretical equation. With unbalanced aids, a group mean ΓLs of +3 or -3 dB was needed for the midline image. The ΓLs for the side images also were shifted. For 12 hearing-impaired subjects with bilateral losses, the midline ΓLs in unaided condition were within the normal range (±2 dB). For two monaural hearing aid users with long experience, the midline ΓLs were greater than normal. The ΓLs for the side images were equal to or greater than ΓLs for normally hearing subjects. In aided balanced and/or unbalanced conditions, some hearing-impaired subjects needed ΓLs for the midline image outside the normal range, and some could not position the image at the side azimuths. It was concluded that the binaural hearing aids can be a source of receiver asymmetry.

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