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As a SHHH member, friend of the Boulder Chapter, and researcher and designer of induction loop assistive listening systems for 25+ years, I am compelled to respond to the article:  "Homemade loop easy, inexpensive" in the April 2005 Boulder Chapter Newsletter (originally published in Albuquerque, NM, SHHH Newsletter).

While it is true that a functioning induction loop system can be assembled using inexpensive Radio Shack components, the reader should be aware of the following facts:

1.  conventional audio amplifiers are designed to power loudspeakers and headphones...not loop wire

2.  even if a proper electrical (impedance) match is achieved so as not to damage the amplifier...performance will be compromised

3.  high frequency response will be the most important performance feature to suffer

4.  loop field strength will be unknown unless the user has a means of measuring it

A true induction loop system will exhibit the following certified performance:

1.  smooth and extended frequency response as per international standards

2.  automatic gain control or signal limiting to maximize signal intelligibility

3.  loop field strength that complies with international standards

4.  guaranteed performance and reliability (imagine what will happen if you tell Radio Shack that you blew their amplifier because you attached a wire to the output)

Loop systems have been around for decades.  One of the reasons they had such a bad "reputation" years ago is because there were no technical standards so individuals and companies made them without any reference to quality performance. 

Today we are fortunate to not only have excellent standards (currently being updated by an international board), but we also have access to first-class technology.

Joshua Gendel, Technical Director at the League for the Hard of Hearing in New York City, recently replaced his facility's Radio Shack "loop amplifier" with a true induction loop amplifier.  After listening to the new system, his response to me was:  "It sounded like the person speaking had removed socks from his mouth!"

Thanks to years of effort by SHHH and more recently, activists like David Myers (see his website:  (http://www.hearingloop.org), the tremendous potential of hearing aid telecoils and compatible assistive technologies is finally being realized.  As an inventor I can appreciate "tinkering"...but when it comes to extracting the best performance and usefulness from hearing aids that are really expensive...why settle for so much less??

As of this writing, Oval Window Audio is the only company in North America researching & manufacturing a full line of induction loop assistive listening systems and related products.

Please contact the author for detailed references on information cited in this article. Norman Lederman, M.S., is Director of Research & Development at Oval Window Audio, 33 Wildflower Court, Nederland, CO  80466,  phone/fax/TDD: 303-447-3607.