Modeling the Influence of Acoustic Coupling of Hearing Aids on FM Signal-to-Noise Ratio Purpose A model was developed to examine variables that influence signal-to-noise ratio (SNR) at the tympanic membrane (TM) when using a hearing aid (HA) and frequency modulated (FM) system. The model was used to explore how HA coupling influences SNR. Method To generate the model, HA output was ... Research Article
Research Article  |   June 01, 2015
Modeling the Influence of Acoustic Coupling of Hearing Aids on FM Signal-to-Noise Ratio
 
Author Affiliations & Notes
  • Linda W. Norrix
    University of Arizona, Tucson
  • Dianne Van Tasell
    University of Minnesota, Minneapolis
  • Jessie Ross
    University of Arizona, Tucson
  • Frances P. Harris
    University of Arizona, Tucson
  • James Dean
    University of Arizona, Tucson
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication.×
  • Correspondence to Linda W. Norrix: norrix@email.arizona.edu
  • Editor and Associate Editor: Larry Humes
    Editor and Associate Editor: Larry Humes×
Article Information
Hearing & Speech Perception / Acoustics / Hearing Disorders / Hearing Aids, Cochlear Implants & Assistive Technology / Research Articles
Research Article   |   June 01, 2015
Modeling the Influence of Acoustic Coupling of Hearing Aids on FM Signal-to-Noise Ratio
American Journal of Audiology, June 2015, Vol. 24, 178-187. doi:10.1044/2015_AJA-14-0035
History: Received July 30, 2014 , Revised December 2, 2014 , Accepted January 11, 2015
 
American Journal of Audiology, June 2015, Vol. 24, 178-187. doi:10.1044/2015_AJA-14-0035
History: Received July 30, 2014; Revised December 2, 2014; Accepted January 11, 2015

Purpose A model was developed to examine variables that influence signal-to-noise ratio (SNR) at the tympanic membrane (TM) when using a hearing aid (HA) and frequency modulated (FM) system. The model was used to explore how HA coupling influences SNR.

Method To generate the model, HA output was measured in a coupler. Known coupler to real-ear transformations and known values for vent (gain) loss as a function of coupling were also used. The model was verified by measuring sound pressure level (SPL) at the TM in 6 ears.

Results The model predicts similar overall SNRs at the TM regardless of coupling method when HA and FM microphones are active. The primary difference in SNR is in the low frequencies and depends on the amount of low frequency insertion gain and the noise levels at the HA and FM microphones.

Conclusions A model was developed to explore how complex variables contribute to SNR at the TM. One variable, HA coupling, is predicted to have only a minimal effect on SNR at the TM when there is HA gain. Further studies will be needed to assess the real-world effectiveness of an FM system coupled to an open- versus closed-fit HA.

Acknowledgments
This research was funded by a grant provided to the University of Arizona: Speech, Language, and Hearing Sciences from Oticon USA (principal investigators: Linda W. Norrix, James Dean, and Frances P. Harris).
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