Download PDF
Semin Hear 2003; 24(1): 029-042
DOI: 10.1055/s-2003-37907
Copyright © 2002 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

Telecoils: Principles, Pitfalls, Fixes, and the Future

Jerry L. Yanz, David Preves
  • Micro-Tech Hearing Instruments, Inc., Plymouth, Minnesota
Further Information

Publication History

Publication Date:
13 March 2003 (online)

    Permissions and Reprints

ABSTRACT

This article will review the principles of inductive coupling for hearing aids, upon which telecoil success depends. The authors will explore some of the design issues that have been solved in the past, others that are just now approaching solutions, and still others that will depend on the success of current and ongoing development efforts. Use of inductive coupling for bringing the telephone signal into hearing aids via a telecoil, in comparison with acoustic coupling, has the advantages of reduced acoustic feedback and environmental noise problems. Inductive coupling, however, may have difficult-to-remove interference pickup from electromagnetic signals produced by common objects. In recent years, the effectiveness of inductive coupling has been helped greatly by adding an integral preamplifier to the induction coil assembly, multimemory programmable hearing aids with a dedicated memory for telephone use, and knowledge of how to best position the telecoil within the hearing aid. Innovative features such as the automatic telecoil switch have made listening via telecoil even easier by eliminating the need to switch modes manually. Future improvements for coupling telephones to hearing aids may incorporate wireless technologies other than induction.

KEYWORDS

Induction - telecoil - magnetic - preamp - interference - wireless

REFERENCES

  • 1 Levitt H. The nature of electromagnetic interference.  J Am Acad Audiol . 2001;  12 322-326
    PubMedGoogle Scholar
  • 2 Lybarger S. Development of a new hearing aid with magnetic microphone.  Electrical Manufacturing 1947;November.
    PubMedGoogle Scholar
  • 3 Goldberg H. Acoustic coupling won't work.  Hearing and Speech . 1975;  43 15-16
    PubMedGoogle Scholar
  • 4 Giddings P. An introduction to electromagnetic compatibility (EMC) and electromagnetic interference (EMI) for audio system designers.  J Audio Eng Soc . 1989;  7/8 570-585
    PubMedGoogle Scholar
  • 5 Madaffari P, Stanley K. Microphone, receiver, and telecoil options: past, present and future. In: Valente M, ed. Hearing Aids: Standards, Options, and Limitations New York: Thieme 1996: 140
    Google Scholar
  • 6 Compton C. Providing effective telecoil performance with in-the-ear hearing instruments.  Hear J . 1994;  47 23-26
    PubMedGoogle Scholar
  • 7 Tannahill C. Performance characteristics for hearing aid microphone versus telephone and telephone/telecoil reception modes.  J Speech Hear Res . 1983;  26 195-201
    PubMedGoogle Scholar
  • 8 Saks D. Telephone/hearing aid compatibility past-present-future.  Audecibel . 1984;  Summer 22-24
    PubMedGoogle Scholar
  • 9 Carlson E. Magnetic field measurements about Bell system hand-sets, Industrial Research Products, Report dated 2-4-83 . 
    Google Scholar
  • 10 EIA Standard RS-504 Magnetic Field Intensity Criteria for Telephone Compatibility With Hearing Aids. Washington, DC: Electronic Industry Association 1983
    Google Scholar
  • 11 Davidson S A, Noe C M. Programmable telecoil responses: potential advantages for assistive listening device fittings.  Am J Audiol . 1994;  3 59-64
    PubMedGoogle Scholar
  • 12 Self Help for Hard of Hearing. SHHH position paper. Importance of telecoils.  Hearing Loss . 1996;  17
    PubMedGoogle Scholar
  • 13 Dillon H. Hearing aid systems. In: Dillon H, ed. Hearing Aids New York: Thieme 2001: 48-73
    Google Scholar
  • 14 Preves D. Standardizing hearing aid measurement parameters and Electroacoustic performance tests. In: Valente, M ed. Hearing Aids: Standards, Options and Limitations. New York: Thieme 1996: 1-71
    Google Scholar
  • 15 Lederman N, Hendricks P. Induction loop Assistive listening systems: a venerable technology meets the new millennium.  Semin Hear . 2002;  24 81-92
    PubMedGoogle Scholar
  • 16 IEC 118-4 Hearing aids: magnetic field strength in audio frequency induction loops for hearing aid purposes. International Electrotechnical Commission 1981
    Google Scholar
  • 17 Preves D. A look at the telecoil-its development and potential.  SHHH Journal . 1994;  15(Sept/Oct) 7-10
    PubMedGoogle Scholar
  • 18 Revit L. Proper use of telecoils: it's as easy as 1, 2, 3, 4! . Available at www.frye.com/library/application/larry.html 1996
    Google Scholar
  • 19 Agnew J. Hearing aid adjustments through potentiometer and switch options. In: Valente M, ed. Hearing Aids: Standards, Options, and Limitations New York: Thieme 1996: 210-251
    Google Scholar
  • 20 Motorola Semiconductor Products Sector. Available at www.motorola.com/webapp/sps/site/overview.jsp?nodeId=03M0ymVXlR5M0zjwd2m1 2002
    Google Scholar
  • 21 HIMSA. Streaming audio demonstration. American Academy of Audiology Convention, Philadelphia, PA, April 17-20, 2002
    Google Scholar
  • 22 Anderson J. Wireless remote processor U.S Patent # 5,721,783; 1998. 
    Google Scholar
  • 23 Wireless Computing. PDAs & Cell Phones-Converging Technologies. Vol. 8, No. 5, Smart Computing Learning Series. Lincoln, NE: Sandhills 2002
    Google Scholar
  • 24 Gladstone V, Kahl E. Performance characteristics of hearing aid compatible and incompatible telephone receivers. Poster Session presented at the Annual Meeting of the American Speech-Language-Hearing Association, Cincinnati, OH, November 18-21, 1983
    Google Scholar
  • 25 Starkey Laboratories. Automatic Telephone Circuit Specification Sheet. Minneapolis, MN 1976
    Google Scholar
      >