title: Waveguide model of the hearing aid earmold system.
abstract: BACKGROUND
  The earmold system of the Behind-The-Ear hearing aid is an acoustic system that modifies the spectrum of the propagated sound waves. Improper selection of the earmold system may result in deterioration of sound quality and speech intelligibility. Computer modeling methods may be useful in the process of hearing aid fitting, allowing physician to examine various earmold system configurations and choose the optimum one for the hearing aid user.
  
  
  METHODS
  In this paper, a computer model adequate for this task is proposed. This model is based on the waveguide modeling method. The waveguide model simulates the propagation of sound waves in the system of cylindrical tubes. Frequency response of the hearing aid receiver is simulated in the model and the influence of the ear canal and the eardrum on the earmold system is taken into account. The model parameters are easily calculated from parameters of a physical hearing aid system. Transfer function of the model is calculated and frequency response plots are obtained using the Matlab system.
  
  
  RESULTS
  The frequency response plots of the earmold model were compared to the measurement plots of the corresponding physical earmold systems. The same changes in frequency responses caused by modification of length or diameter of a selected waveguide section, are observed in both measurement data of a real earmold system and in computed model responses.
  
  
  CONCLUSIONS
  Comparison of model responses obtained for various sets of parameters with measurement data proved that the proposed model accurately simulates the real earmold system and the developed model may be used to construct a computer system assisting the physician who performs earmold system fitting.
authors.affiliation: Multimedia Systems Department, Gdansk University of Technology, Narutowicza 11/12, Gdansk, Poland. greg@sound.eti.pg.gda.pl
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Szwoch
authors.forename: Bozena
authors.initials: B
authors.lastname: Kostek