Kudos to us for making accessibility a priority!

By Ruth Bentler and Kassie McLaughlin

Ruth Bentler
Ruth Bentler

The University of Iowa has made a huge commitment to persons with hearing loss in its decision to loop all upcoming construction on the campus! As a result of the devastating flood of 2008, a number of buildings were damaged and will now be rebuilt at higher elevations (yes, even Iowa City has different elevations!). These include a new performing arts building, a new School of Music building, and a new Art Education building, to name only a few.

The decision of the planning committee to include loops in all public spaces (including classrooms) is noteworthy and should serve as a model for other universities as they consider both their responsibilities to persons with hearing loss as well as their fiscal responsibilities during building and remodeling.



The University of Iowa folks certainly did their homework into arenas, accessibility provision, and cost. Why did they choose induction loops? Because they are relatively easy to install, maintain, and use. But we are getting ahead of ourselves. Let’s review, briefly, the concept.

Kassie McClaughlin
Kassie McLaughlin

In order to understand how induction loops work, an overview of the telecoil in the hearing aid is necessary. Within hearing aids, a coil of wire is wrapped around a ferrite material, such as iron, which is an efficient conductor of electromagnetic signal. Telecoils are standard in many hearing aids on the market.

Induction is the process of an electrical current inducing a voltage from a distance. An induction loop is a wire placed around a space, such as a classroom, that converts audio information from a microphone into an electromagnetic signal that the hearing aid’s telecoil can receive. The listener picks up the signal from the talker’s microphone directly (via the telecoil) rather than via the hearing aid microphone, which will also pick up environmental noise between the talker and the listener.

Induction loops fall into a category of instruments called assistive listening devices (ALDs). ALDs can help those who are hearing impaired by improving the signal-to-noise ratio, increasing the ease of listening, and allowing users to listen at a greater distance.

George Kahl, an Iowa City resident and loop user, owned and managed an assistive listening device store (called Sound Clarity) and has installed many loop systems over the years. He notes that he prefers the sound quality from loop systems over that from other ALDs he has tried to help him cope with his own hearing loss.

Because loop systems transmit the signal directly to his hearing aid, he finds that he gets greater improvement in the signal-to-noise ratio than hearing aids alone could ever provide, even those with directional microphones or noise-reduction schemes. Because the intended signal (music, speech, or the like) is sent directly to the hearing aid, other background noises are not amplified in the way they typically would be from the hearing aid microphone.

Another advantage of a loop system is that many hearing aid users already own the equipment (i.e., a telecoil) necessary to use it in venues where loops have been installed. Hearing aid users can simply switch to the telecoil mode and listen. People with unaided hearing losses or incompatible devices can check out equipment from most venues and listen to the intended signal through earphones.

In addition, using an induction loop meets the requirements set forth by the American Disabilities Act, specifically the 2010 ADA Standards for Accessible Design, which has a mandate deadline of March 15, 2012 for hearing instrument compatibility.



One limitation of induction loops compared to other similar systems, such as infrared and FM, is that signals can leak from one area to another. For example, patrons in a movie theater may pick up not only their own movie’s sound track, but also the overflow sound from the movie in the next theater. Spillover can also be a concern when privacy is important. However, in locations where there is only one signal that all patrons need to hear, the induction loop is a great option.

A second limitation of a hearing loop system is the cost of installation. The larger the loop system, the more expensive the installation. Looping a facility when it is under construction, as is the case here on the University of Iowa campus, is the most cost-efficient way to go.



Loop systems are already commonly used in Europe. For example, in Britain, nearly all churches, auditoriums, and cathedrals are looped. So are Heathrow Airport, many train stations, the Tower of London, and taxicabs in Edinburgh.

Recently, loop systems have started to gain acceptance in the United States as well, in large part due to the grassroots movement started by David G. Myers and his group at hearingloop.org. In New York City, the Taxi and Limousine Commission has started a pilot study to investigate induction loops in taxicabs, and all the ticket booths in that city’s subway system are looped. Sertoma (SERvice TO MAnkind) has launched the Sound Investment Campaign, helping to improve access for those who are hearing impaired. All of this bodes well for those individuals who need a little boost in signal-to-noise ratio in their everyday environments.

Our own university planners here in Iowa deserve kudos for continuing this trend. They needed and accepted input from us in Communications Sciences and Disorders. Perhaps other universities can follow suit. If other Audiology Departments do a little pushing and shoving, as we did, campuses across the country can set the accessibility standard for all public places.


Ruth Bentler, PhD, is Professor and Chair of the Department of Communication Sciences and Disorders at the University of Iowa. Because of her work with hearing aids and acoustical factors that impact their effectiveness, she has served as a consultant to the university’s planning and building committees many times over the years. Kassie McLaughlin is an AuD student at the University of Iowa. She works in the Hearing Aid Lab on various projects related to hearing aid efficacy and effectiveness.


  1. Today I spoke with someone who frequently attends the Fox Cities Performing Arts Center in Appleton WI. The first thing she told me that the loop never worked better for the show War Horse. She was absolutely thrilled!

    Mr. Schwartz just keeps saying over and over, and proving with the same involved calculations, that hearing loops will not work – yet they do. Why argue with thousands of users who sit in their TV rooms, houses of Worship or in lecture halls enjoying and understanding the sound so much better, and all this via the telecoil of their hearing aids or cochlear implants? What is it to him?

  2. Ruth writes: “… patrons in a movie theater may pick up not only their own movie’s sound track, but also the overflow sound from the movie in the next theater.”

    This should not be the case with a properly installed “”phased array” loop installation, which was invented to control leakage of the audio signal outside the loop. It works quite well and enables induction loop systems to be installed in two adjacent theaters or classrooms without interference.

    The key, of course, is “properly installed.” Good design and installation of a loop system is critical.

  3. Dan Schwartz’s comments about Bluetooth cite just one example of the many exciting developments in technology that are making hearing aids more versatile and functional. None of them however, can provide group aural communication access in a church, a theater, a council chamber or the 14,000 seat Breslin Center at the Michigan State University or a lecture hall at the University of Iowa.

    AFILS (Audio Frequency Inductiion Loop Systems – hearing lops), FM and Infra Red can, but only AFIILS does so without the need for a receiver and a headset for most hearing aid or cochlear implant users. Engineers at Widex (a major hearing aid manufacturer) say it will be 15 years of more before any universally accessible technology may be available to replace AILS/FM/IR.

    Induction loops are about as obsolete as the internal combustion engine and are the most user friendly and reliable technlogy available today. My thanks to Ms. Bentler, Ms McLaughlin and the other officials at the University of Iowa for this initiative to make your campus more hearing aid accessible for today’s and tomorrow’s students.

    Stephen O. Frazier, Hearing Loss Support Specialist

  4. What a spirited response, Dan! In fact, the people in charge here in the nearly billion dollars’ worth of building and renovation ate lots of dog food before choosing how to make each venue accessible to persons with hearing loss. In addition to the many acoustic engineers, they listened to a number of our own experts, the likes of Cindy Compton, Marshall Chasin, Brian Fligor, and Mead Killion, to name a few. Everyone is pretty secure in the process. Thanks for your opinion.


      Professor Bentler, I just rediscovered this, so please pardon the delay.

      To clarify, when I wrote “eat their own dog food” I meant advocates who are actually hearing impaired themselves.

      As for your new buildings using baseband induction “hearing” loops, is each installation fully compliant with IEC 60118-4: 2006 standards for field strength, frequency response, and most importantly, noise? How much was actually spent on each installation, including remediation of the installed electrical system for electromagnetic interference (noise)? And, what is the energy consumption of all of these loop amplifiers? And, do the loop amplifiers meet fire codes for public assembly areas by having full UL listing? (Better go look on the back, as if it’s Ampetronic, it is .NOT. UL listed)


      Of the list of people above, only Mead Killion is a fellow Electrical Engineer (and a damn good one); though Brian Fligor is a Biomedical Engineer, who has a good grasp on signal theory.

      The problems with baseband induction “hearing” loops — Especially here in the United States — are manifold; but mainly they revolve around these key areas.

      • 60 Hz **and harmonics** electromagnetic interference (EMI, i.e. noise) from our electrical power distribution system, both on the utility level and on the building branch circuit wiring level:

      A) Here in the US, homes use 120-240 volt wiring, while commercial buildings use 120-208 volt wye or 120-240 volt center-tapped delta for their wiring plant; while in UK they use 230V for residential & 230-380V wye for commercial — For a given amount of power, when you halve the voltage, you double the current, and since it is the alternating flow of current that generates the B-field (or H-field), immediately we in the US have double the EMI that our friends in UK & EU have, right off the bat;

      B) But wait, there’s more! Here in the US, because of dirt-cheap electricity prices, our commercial buildings use perhaps 50% more electrical energy per ft² as lighting loads are higher (dimly lit spaces beget trip & fall lawsuit liability), and also more reliance on HVAC due to less building insulation. So, we’ve already doubled the current from our lower voltage, and need to bump it up by another 50% more because we’re energy hogs;

      [Corrected paragraph]
      C) Oh, and One More Thing: Here in the US, our power distribution system supplies “dirtier” electricity than elsewhere: Any time a sinusoidal voltage waveform is subject to non-linearities in circuit impedance, it suffers from harmonic distortion proportional to the non-linearity. Magnetic hysteresis, which is the forced reorientation of the crystalline-sized magnetic domains in ferromagnetic material, such as iron, steel, and some rare earths (remember this principle, as we’ll use it again), presents just such a highly non-linear circuit impedance. Although iron core transformers are universal throughout the world, here in the US, because the cost of electricity is inexpensive compared to the cost of capital for investor-owned utilities, and also because over the last 35 years wire insulation has improved resistance to thermal breakdown with NEMA Class H (110°C) ratings, here in the US the transformers are run hotter than in UK & EU, as the typical transformer nameplate rating is ≈110% of the saturation flux density Φ(sat), where Φ = n(∂φ/∂t) …See the picture at:

      Put another way, when you convolve a 60 Hz sinusoid with the highly nonlinear transfer function represented by the hysteresis “loop” curve, you get strong harmonics right up into the kilohertz range, which is happily picked up by the induction “telephone” coil, amplified, and piped right into the listeners’ ears… And since this interference is in the audio band, by the very nature of the beast operating in the baseband (as opposed to riding on a modulated carrier), it cannot be filtered out.

      D) Major loop proponent and hardware builder Ampetronic recognizes these factors: At the just-concluded InfoComm in Orlando, as well as other venues, they always demonstrate their systems with a continuous audio track in their attempt to mask in-band interference.

      For more on the power systems issues, please see Prof. James Maxted, 1126 Seamans Center; and for more on the electromagnetics issues, please see Prof. David Andersen, 132 Iowa Advanced Technology Laboratories.

      • In addition to much more interference that cannot be filtered out, our building codes and construction techniques are much different here in the US than in UK & EU: Because of hurricanes, tornados and earthquakes, we use much more steel and steel-reinforced concrete than across the pond. When you watched the buildings on your campus being built, you saw reinforcing bars embedded in the concrete floors, steel I-beam members, and steel decking for upper floors and the roof. Also, when you look up from where you are sitting, you’ll see the straps used to hold the acoustical ceiling tiles in place are aluminum:

      A) All metals conduct electricity to a varying degree, and anytime you have a metallic loop (such as each 12 feet of strap surrounding a 2×4 foot ceiling tile) placed in the changing magnetic flux from an induction loop system, a corresponding voltage proportional to (∂φ/∂t) is induced in these single-turn secondary “transformers” …And this induced voltage will both distort the magnetic flux lines, and also create i²R power losses independent of frequency (in the audio frequency range) that must be compensated for by larger loop “driver” amplifiers;

      B) Remember six paragraphs above where I beseeched you to remember “hysteresis,” as it would rear its’ ugly head again? Well, as it turns out, all of that square footage of roof decking, and all of those steel I-beems & rebars used to make our buildings hurricane/earthquake/tornado proofing? Well, each half-cycle of the magnetic field generated by the hearing loop needs to “flip” the crystalline-sized magnetic domains in every piece of iron & steel its the path… And contrary to what was stated at the 2nd International Loop Conference two years ago in DC, hysteresis loss is monotonically proportional to the frequency up until Φ(sat) is reached. Because of these additional losses, additional high frequency compensation must be applied to the loop driver amplifier; and if the amplifier cannot supply this additional voltage across the terminals with respect to the power supply rails, the high frequencies will be rolled off.

      [For just one particular Wisconsin facility, we find “an impressive structure, the Fox Cities Performing Arts Center was built using more than 21,000 cubic yards of concrete, 3.3 million pounds [1650 tons] of reinforcing steel and 530 tons [1,060,000 pounds] of structural steel.]♦

      • We have the argument that T-coils in hearing aids are “already there, ready to be used, and no additional equipment needs to be checked out.” This is a specious argument on two grounds:

      A) Only 8.5 million people wear hearing aids (+150k with CI’s) out of ≈33 million total hearing impaired: The Americans with Disabilities Act basically states that you have to “serve all comers,” i.e. the venue still needs receivers & headphones for the 75% of people who don’t have hearing aids;

      B) But is that 75% figure accurate? Also, according to the Better Hearing Institute, out of the 8.5 million people who have hearing aids, only about 60%, or 5.0 million, have T-coils: This means that even if you go through the time, expense and hassle to implement a loop system, you still need to supply receivers for the 85% (28 million out of 33 million) hearing impaired patrons who do not have T-coil -equipped hearing aids.

      • Energy consumption: Of the four transmission technologies for assistive devices – FM, Infra-Red, Bluetooth 4.0 digital and baseband induction loop, only induction loops require power in the many tens, even hundreds of watts – And climbs with more ferrous & non-ferrous metals in the field; while IR is in the 10 watt range, and FM & BT is in the single digits;

      • Cost of baseband induction “hearing” loops is through the roof when you add in the cost of remediation to remove noise; but don’t take my word for this: According to advocate Juliëtte Sterkens herself,

      “Dr. Sterkens excitedly reported that she had just received notice of a $20,000 donation toward installing hearing loops at the Fox Cities Performing Arts Center in Appleton, WI… ‘It’s an expensive installation, probably in the $150,000 range, so a donation of that size really makes the job easier,’ she said.”♦♦

      $150 grand to serve only 15% of the hearing impaired patrons? A complete FM system that would cover the entire venue, including the Kimberly-Clark Theater – Not just the Thrivent Financial Hall♦♦♦ — would be just a few thousand dollars; and with the remaining $140,000 purchase 4000 hours of captioning (CART) services, which we in the hearing impaired community really need.

      • “Technology lock-in” from the vacuum tube era: I need to update David Myers’ knowledge base, as he incorrectly states,
      “Bluetooth, because of its limited range, complexity, and battery-drain, does not have the potential to provide listening assistance to all in auditoriums and other larger venues.”

      Although this is correct for Bluetooth 2.1 a/k/a “classic Bluetooth,” this is patently false for Bluetooth 4.0 Low Energy (“BLE”), as it is at the core of the “Made for iPhone” initiative, which addresses both power consumption AND latency problems:

      A) In BT4.0 the range has been extended with three power levels: The 100 µW (-10dBm) level that provides the 30 foot range of classic BT; plus the newer 1.0 mW (0dBm) level that provides a 500 foot range which will be used for the “Internet of Things” (IoT) as well as for broadcasting to MFI hearing aids & CI’s in larger public venues; and for distances in the mile range, 10 mW (+10dBm) levels are available;

      B) As the name implies, Bluetooth Low Energy is designed for low power applications, with the standard being a coin cell battery will power the device for at least one year:

      B1) In the first quarter of 2013, fully 80% of BTE’s and 70% of all hearing aids shipped with wireless capability, i.e. the ability to receive streamed audio. Wireless hearing aids that have streaming capability have been around since at least 2007, and they are rapidly becoming the rule, not the exception. What’s more, every hearing aid that can receive streaming audio will be able to receive Bluetooth 4.0 broadcasts, either with a streamer upgrade, or even better, for owners of the Siemens miniCom or Oticon Streamer Pro, already in place as these devices support BT4.0.

      B2) Although no currently shipping hearing aids support BLE inside the package, they are just about to roll out from the Big Six hearing aid manufacturers, most likely with GN ReSound & Starkey first out of the gate due to their use of FPGA architecture; while Widex brings up the rear with the long design cycle due to their use of ASIC architecture and concomitant validation process before committing to silicon.

      I could go on and on as to why baseband induction loops are a Bad Choice for the United States, such as our quickly increasing reliance on SCR and triac-based inverters for energy efficiency in motors used in devices like HVAC blowers and home appliances, and light dimmers; but I’ll have much more in The Hearing Blog in an illustrated 6-part series.

      Dan Schwartz,
      Editor, The Hearing Blog

      ♦ The History of The [Fox Cities Performing Arts] Center

      ♦♦ A Surge in Hearing Loops Gives Hearing-Impaired Front Row Seats (Hearing Journal, September 2012)

      ♦♦♦ Accessibility | Fox Cities Performing Arts Center

      Original article: Kudos to us for making accessibility a priority!

  5. Kudos to Ruth Bentler and Kassie McLaughlin for their excellent essay, and to my alma mater, the University of Iowa for providing a national model of hearing accessibility.

    Hearing loops are about as old as computers, and likewise exist in modern forms that have recently spread across Scandinavia and the UK (where they are now at 11,500 post offices, in all London taxis, and in thousands of larger public spaces, including most cathedrals and churches with PA systems).

    Alas, Bluetooth, because of its limited range, complexity, and battery-drain, does not have the potential to provide listening assistance to all in auditoriums and other larger venues.

    And thankfully, the hearing loop cost for most auditoriums and worship places is about what one person today might pay for a pair of high-end hearing aids. Indeed, because so many more people will use hearing assistance that is directly hearing aid compatible, the cost per user (in our West Michigan experience) is far less than with IR and FM receiver/headset units, which deliver generic sound . . . and which people must take the initiative to locate, check out, and return. (My community’s seven-screen theatre complex told me that their receiver/headset units–which produce unsatisfactory results for most of us–get used “about once per month per theatre.”) We can do better–and we are, and with thousands of happy people.

    Are hearing loops the last word in assistive listening? Likely not. . . though whatever replaces them in Scandinavia, the UK, the USA and elsewhere will need to be similarly simple for people of all ages to operate, affordable to the user, available with most hearing instruments, energy efficient, scalable to venues both small and vast, and universal rather than proprietary.

  6. Thank you for “helping” the hearing impaired community by locking in a noisy and obsolete technology, especially with wireless direct-to-hearing aid communications comprising 70% of all hearing aids sold & 80% of all BTE’s.

    And, before you throw out the canard that the manufacturers all have different standards, in fact the 2.45 gHz Buetooth 4.0 Low Energy (BLE) has been standardized by the “Made for iPhone” logo program for CI’s as well as hearing aids.

    Unfortunately, baseband induction loop “technology” is something that looks good on paper; but as you alluded to above, the cost can be extravagent: Juliette Sterkens spent $150,000(!) to install a loop system at the Fox Valley Theater in Wisconsin, mostly on remediation for electromagnetic interference.

    Please do us in the hearing impaired community a favour, and “eat your own dog food” before pushing obsolete, troublesome technologies upon us, locking it in when better technology is around the corner.

    Dan Schwartz,
    Editor, The Hearing Blog

    1. Instead of being critical of your comment, I will instead ask you to prove your theory. Let’s use your example at Fox Valley. I am not sure what the seating capacity is, but lets just say that on a given performance their are 50 people in attendance that need Hearing Assistance. Using your blue tooth theory, please tell me how you will connect the house sound system directly to 50 people and how much it will cost? And then tell me how those same people could go to many other venues in their town and do the same thing, without having to check out any special listening device.

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