For the next couple of weeks Hearing International will review Induction Loop Systems and consider the status of their use in the international community. In the past couple of years, at least in the US, we have heard a lot about the use and proliferation of induction loop systems and how beneficial they could be to the hearing impaired if they were available in more places. A project spearheaded by the Hearing Loss Association of America and the American Academy of Audiology called “Get in the Hearing Loop” with a goal of increasing the use of induction loops across the US.  Kirkwood (2011) indicates that the”Get in  the Loop” project is beginning to have some steam in the United States indicating a major chain of theaters has signed on to the project and National Public Radio has just lately informed the public on the benefits of these systems.   Although this is a major effort to “Loop America”, these induction loops have been used for years in Europe for churches, public buildings, in private businesses and elsewhere.  Audiologists everywhere have known for quite some time that induction loops are an inexpensive, assistive listening device that can be used effectively by a major share of the hearing impaired in a variety of situations.    In the USA, induction loops made their first appearance as an imported product after World War II and initially generated significant interest that peaked in the late 1960’s and early 1970’s, especially in schools for deaf and hard of hearing children.  Although there are many reasons why US interest waned and later lagged behind in the use of induction loop technology and was replaced by the availability of improved AM, FM and infrared technologies that offered great benefit.  Further, during the past 3-4 decades, Americans generally used smaller in-the-ear hearing instruments that were not generally equipped with telecoils to utilize induction loops technology. Meanwhile, 0ver 85% of Europeans used behind-the-ear instruments with telecoils spurring the use induction loops (Blaha, 2004).

http://www.youtube.com/watchv=gYM7muecd_o&feature=player_detailpage

Currently, in the US and around the world, induction loops are seen as an inexpensive method of augmenting hearing aid performance in places of worship, cinema,playhouses, public buildings and other places.`

Where did These Loops Come From?

Hendricks and Lederman (2011)  report that 1998 marked the 60th anniversary of induction loop systems and hearing aid telecoils. The first patented magnetic induction loop communication system was invented by Joseph Poliakoff in Great Britain in 1937. The first wearable hearing aid to incorporate a telecoil and capable of using an induction coil is reported to be the Multitone VPM in 1938 (pictured left, Bauman, 2011a).  The Multitone VPM (Vest Pocket Model) was manufactured by the Multitone Electric Co. Ltd. of London, England and was very small for its time measuring 3¼” by 2½” by 1”.  Bauman (2011a) The first portable hearing aid to incorporate a telecoil was the first instrument to be able to use the induction loop system invented by Poliakoff.

How Do These Systems Work

There are actually quite a number of references on the net to how induction loops work to amplify sound.  While most are from manufacturers or distributors of these products, Rudisill (2010) writes that loop systems and telecoils work together with hearing aids to help hard-of-hearing people hear better.  On another detailed site presenting the specifics of how these systems work, Bauman(2011b) presents that a loop system consists of three basic components: a microphone or other input device, a loop amplifier, and a loop of wire. Hearing instruments equipped with telecoils make up the receiving side.  She further indicates the simplicity of these systems.  All that is necessary to set up an induction loop system is to plug the loop amplifier into a wall socket, plug, an input device (such as a microphone) into the loop amplifier, string a loop of wire around the perimeter of the listening area, connect the ends of the wire to the loop amplifier, and turn it on.  As presented in the illustration by Compton (1991) (Left) Audio signals are picked up by the microphone or directly from some sound source like a TV or stereo, amplified by the loop amplifier and travel through a loop of wire  surrounding the listening area. The wire loop is used instead of (or in addition to) regular loudspeakers. As the sound signal travels through the loop of wire, it produces a magnetic field in the looped area that mirrors the frequency and intensity characteristics of the original sound signal.  Now, it is the hearing aid telecoil’s job to convert the loop’s magnetic signal into sound that can be heard. When the switch on the hearing aid moves from microphone (M) to telecoil (T), what;s happening is theat the hearing instrument is connecting a small coil of wire to the input of the hearing aid’s amplifier instead of its microphone. This tiny coil of wire is sensitive to nearby magnetic fields such as the one produced by the loop system. The changing magnetic field in the room loop induces a corresponding electrical signal into the telecoil. The hearing aid amplifier then amplifies this signal and a faithful reproduction of the original speech signal is heard (Bauman, 2011b).

Benefits/Limitations

Rudisill (2010) offers a concise discussion of the benefits and limitations of these induction  l0op systems.

1.  Loop/telecoils have several big advantages over regular hearing aids

A. No feedback !

B.  You don’t hear everything — there is less noise.

C. They are much cheaper than (say) buying a second hearing aid.

2.  Loop/telecoils also have some problems over regular hearing aids

      A. Telecoils can pick up electrical interference. Loops produce electrical interference.

B. Except for their use in telephones, loops require  some   preparation (i.e wiring).

C. Telecoils take up space, and are not available in very tiny hearing aids.

The main advantage of loop systems is that they are inexpensive ways to hear things like the telephone or TV. The main problem with them is that they may pick up hum or static from electrical equipment and wiring and also that they take up space in the hearing aid.

Rudisill’s Bottom Line

Although some feel that Loops are not a good idea for people with mild hearing problems, Sterkens (2011) feels that those with even a mild hearing impairment using instruments equpped with a telecoil can benefit from the induction loop. Loops are a good idea with people who are struggling to hear, even with powerful hearing aids. FM systems are even better, but they cost more money and take up more space on your ear.

Be here next week when Hearing International will review where the world is in the process of induction looping……

References:

Bauman, N. (2011a). Vacuum tube hearing aids.  The Hearing Aid Museum. Retrieved november 27, 2011:  http://www.hearingaidmuseum.com/gallery/Vacuum%20Tube/OtherMakes/info/multitonevpm.htm

Bauman, N. (2011b). How do loop systems work.  Center for Hearing Loss Help.  Retrieved November 27, 2011:  http://www.hearinglosshelp.com/articles/loopsystems.htm

Blaha, R., Hearing aid telecoils: numbers in the US market.  Masters Thesis:  Ohio State University, Deartment of Speech and Hearing Sciences, 2004.  Retrieved November 27, 2011:  http://etd.ohiolink.edu/view.cgi/Blaha%20Rebecca.pdf?osu1129571996

Compton, C.L. (1991) Assistive Devices: Doorways to Independence. Annapolis, MD: Single-handed Productions.

Hendricks, P. & Lederman, N. (2011).  PartII:  Induction loop systems, history and advancements. Oval Window Audio.  Retrieved November 27, 2011:  http://www.ovalwindowaudio.com/articles/loopworld.htm

Kirkwood, D. (2011). Hearing loop campaign spreads and grows, as does coverage in the media.  Hearing Health and Technology Matters.  Retrieved November 30, 2011:  http://hearinghealthmatters.org/hearingnewswatch/2011/hearing-loop-campaign-spreads-and-grows-as-does-coverage-in-the-media-2/

Rudisill, H., (2010).  Loop systems and telecoils for hearing aids. In T. Hain (Ed) Dizziness-and-balance.com  Retrieved November 27, 2011:  http://www.dizziness-and-balance.com/disorders/hearing/hearing-aids/images/tcoil.html

Sterkens, J., (2011).  Personal communication.  Email comment to author 12-2-2011.

4 Responses to Induction Loops Around the World……Where are we? – Part I

  1. Very nice historical article. Two reflections, from Michigan, where we now have several hundred installations.
    1) Interference has generally not been a problem, and where it has the problem has been solved.
    2) The BIG advantage to hearing loops is that they make assistive listening directly hearing aid compatible–no need, when having trouble hearing, to get up, locate, check out, and wear a conspicuous headset (that delivers generic sound). Rather, just push a button and your own hearing instrument becomes a customized, wireless, in-the-ear loudspeaker. That’s the difference that makes hearing loops a technology that real people with hearing loss will, in much greater numbers, actually use.

    • Bob Traynor says:

      David:

      Sorry I missed you comment last week. Your comments are well taken and loops would be more beneficial if they were available in more places. According to the organizations that know, the US is the fastest growing loop market. From my research I can not find that there is much use of thes loops outside of Europe and North America.

      Thanks for your comment at HHTM…come back anytime!

      Bob

  2. Dana Mulvany says:

    Before installing an audio loop system, there should be a survey of any electromagnetic interference (EMI) in the immediate vicinity. People with telecoils can do this informally by turning on the telecoil and walking around the entire vicinity. If the EMI is significant in one part of the room but not another, it may still be possible to use a loop in the part of the room where the EMI is not strong. It may also be possible to troubleshoot what is causing the EMI and to resolve it. (Dimmer switches, cathode ray tube monitors, and poor wiring can cause EMI.)

    2A above should be corrected to:

    “Activated telecoils will pick up ambient electromagnetic interference from the environment.” (Properly functioning loops do not cause EMI, but simple perimeter loops will have spillover. Generally, large loops should not be placed right next to places where HAC telephones, neckloops or silhouette inductors will be used. For example, spillover from large perimeter loops hugging the walls is why they should not be used next to a workshop room where hard of hearing people will need to use neckloops or silhouette inductors to use IR or FM systems. It is possible to configure a loop installation to minimize such spillover, however.)

    Dispensing professionals interested in optimizing the use of induction technology should look into installing a loop system in their offices that meets the international standard for loop systems. They will then be able to check whether the telecoils in their customers’ hearing aids are working well with certified loop systems. Because the default telecoil program generally does not provide the full frequency response possible (it’s typically designed for the narrow frequency response of landline telephones beginning at 300 Hz), dispensing professionals should ensure they know how to optimize the telecoil program for use with assistive listening technology (which would require the widest frequency response possible and which would allow the telecoil user to enjoy hearing frequencies below 300 Hz). In some cases, it may be desirable to provide two different telecoil programs—one for the telephone and another for assistive listening technology.

    • Bob Traynor says:

      Dana:

      Thanks for your comments…I will probably compile these and do a blog on the grreat comments we received to the Induction Loop series.

      Bob