title: Modeling the Influence of Acoustic Coupling of Hearing Aids on FM Signal-to-Noise Ratio.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
authors: Linda W
authors: LW
authors: Norrix
authors: Dianne
authors: D
authors: Van Tasell
authors: Jessie
authors: J
authors: Ross
authors: Frances P
authors: FP
authors: Harris
authors: James
authors: J
authors: Dean
mesh_terms: D003198:Computer Simulation; D006310:Hearing Aids; D006801:Humans; D059629:Signal-To-Noise Ratio; D014432:Tympanic Membrane