Download PDF
Semin Hear 2003; 24(4): 289-298
DOI: 10.1055/s-2004-815553
Copyright © 2003 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

Chemistry and Rheology of Otoplastic Materials

Vasant V. Kolpe1 , Robert J. Oliveira2
  • 1Company Scientist, Hearing Components, Oakdale, Minnesota
  • 2President, Hearing Components, Oakdale, Minnesota
Further Information

Publication History

Publication Date:
15 January 2004 (online)

Also available at
    Permissions and Reprints

ABSTRACT

Knowledge of ear impression compounds, as well as earmold materials, is important to provide quality-hearing solutions to hearing-impaired people using BTE hearing aids. This article offers a chemist's and a rheologist's review of earmold materials. The sound attenuation properties of silicones, acrylates, and polyurethane foams have been measured using a novel Acoustic Test Fixture (ATF). The authors conclude that of these three polymeric materials, compliant viscoelastic polyurethane foam provides the best current earmold material solution for hearing-impaired individuals. It overcomes the fundamental limitations of shrinkage and mechanical compatibility to the dynamic ear canal. Also, compliant foam provides an ultra soft modulus at body temperature and superior energy dissipation capability in the audible acoustic range of frequencies.

KEYWORDS

Earmold materials - impression compounds - silicone - acrylates - polyvinylchloride - viscoelastic foam - polyurethane foam - rheology - acoustic test fixture - foam earmolds - otoplastics

REFERENCES

  • 1 Dalsgaard S C. Earmolds and Associated Problems.  Stockholm: The Almquist & Wiksell Periodical Co.; 1975
    Search in Google Scholar
  • 2 Berger K. Hearing Aid.  Livonia, MI: Hearing Aid Industries Association; 1984
    Search in Google Scholar
  • 3 Valente M, Hosford-Dunn H, Roesser R. Audiology, Diagnosis, Treatment and Practice Management. New York: Thieme 2000
    Search in Google Scholar
  • 4 Dillion H. Hearing Aids. New York: Thieme 2001
    Search in Google Scholar
  • 5 Oliveira R, Hoeker G. Ear canal anatomy and activity.  Semin Hear . 2003;  24 265-275
    Thieme ConnectPubMedSearch in Google Scholar
  • 6 Bryan, et al. United States Patent 4,657,959; April 14, 1987 . 
  • 7 Humes L E, Wilson D, Humes L. et al . Comparison of two measures of hearing and satisfaction in a group of elderly hearing and wearers.  Ear Hear . 2002;  23 422-427
    CrossrefPubMedSearch in Google Scholar
  • 8 Bailey W. Cationic polymerization with expansion in volume.  Journal of Macromolecular Science: Chemistry . 1975;  A9 849-865
    PubMedSearch in Google Scholar
  • 9 Cook W. Structure and properties of methacrylate based dental restorative materials.  Biomaterials . 1985;  6
    PubMedSearch in Google Scholar
  • 10 Rodriguez F. Principals of Polymer Systems, 3rd ed. New York: Hemisphere Publishing; 1989 . 
  • 11 Smith K, Oliveira R. Feedback .  2001;  12 2
    PubMedSearch in Google Scholar
  • 12 ASTM D-2240-86 “Rubber Property-Durometer Hardness. American Society of Testing Materials; Yearbook 1990
    Search in Google Scholar
  • 13 Tobolsky A. Properties and Structure of Polymers.  New York: John Wiley; 1962
    Search in Google Scholar
  • 14 Ferry J. Viscoelastic Properties of Polymers.  New York: John Wiley; 1994
    Search in Google Scholar
  • 15 Kolpe V, Oliveira R. Poster presentation at International Hearing Aid Conference, Lake Tahoe, CA, August 2002 .