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Semin Hear 2003; 24(4): 299-312
DOI: 10.1055/s-2004-815552
Copyright © 2003 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

Earmold Acoustics

Mead C. Killion
  • President, Etymotic Research, Inc., Elk Grove Village, Illinois
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Publication History

Publication Date:
15 January 2004 (online)

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ABSTRACT

Several fitting disappointments can be traced directly to improper earmold acoustics introduced by the earmold impression, or the instructions to the earmold laboratory, or to the earmold laboratory itself. To understand these disappointments requires some understanding of why earmolds do what they do to the sound passing through them. The reader possessing a certain eagerness to learn may find the present description (labeled theory) novel and useful. Following that theoretical description, an argument is made that many of the problems of occlusion effect and feedback can be alleviated by the proper use of a comfortable deeply-sealed earmold (requiring good impressions beyond the second bend, of course). The performance of actual earmolds is used throughout to illustrate the points made here.

KEYWORDS

Horns - resonance - damping - choked - sound channels - earmolds

REFERENCES

  • 1 Bergenstoff H. Recent development in hearing aid design and fitting techniques. Lecture at Rehabilitation through Amplification, June 21-25, 1980, Chicago, IL
  • 2 Lybarger S. Earmolds. In: Katz J, ed. Handbook of Clinical Audiology Baltimore, MD: Williams & Wilkins 1972: 602-603
    Search in Google Scholar
  • 3 Dillon H. Hearing Aids. Sydney, Australia: Bomerang Press; 2001 2001
    Search in Google Scholar
  • 4 Bergenstoff H. Earmold design and its effect on real ear insertion gain.  Hear Instr . 1983;  9 46-49
    PubMedSearch in Google Scholar
  • 5 Libby E. Achieving a transparent, smooth, wideband hearing aid response.  Hear Instr . 1981;  10 9-12
    PubMedSearch in Google Scholar
  • 6 Killion M. Earmold options for wideband hearing aids.  J Speech Hear Dis . 1981;  1 10-20
    PubMedSearch in Google Scholar
  • 7 Killion M. Equalization filter for eardrum-pressure recording using KEMAR manikin.  J Audio Eng Soc . 1979;  27 13-16
    PubMedSearch in Google Scholar
  • 8 Killion M. Damper for hearing aid. U.S. Patent #6,047,075, 2000
  • 9 Killion M. Earplug with improved audibility. U.S. Patent #4,852,683, 1989
  • 10 Killion M. Electronic damper circuit for a hearing aid and a method of using the same, U.S Patent #5,812,679, 1998
  • 11 Heaviside O. Cases of vanishing or constancy of the reflection coefficients. In: Electromagnetic Theory, 1899, Vol II:80. New York: Dover Publications; reprinted in 1950
    Search in Google Scholar
  • 12 Killion M. Earmold design: theory and practice. In: Jensen J, ed. Hearing Aid Fitting Theoretical and Practical Views 13th Danavox Symposium; Copenhagen, Denmark, October 4-7, 1988
  • 13 Killion M. Talking hair cells: what they have to say about hearing aids. In: Berlin C, ed. Hair Cells & Hearing Aids San Diego, CA: Singular 1995: 125-172
    Search in Google Scholar
  • 14 Killion M. Earplug with improved audibility, U.S Patent #4,852,683, 1988
  • 15 Carlson E, Mostardo A. Dampoing Element. U.S. Patent #3,930,560, 1976
  • 16 Killion M. Zwislocki was right.  Hear Instr . 1988;  1 14-18
    PubMedSearch in Google Scholar