Forum Proceedings

Summary

Manufacturers, researchers, clinicians and other stakeholders have identified technology needs in the field of Inductive Loop Assistive Listening Systems (ALS). High priority technology needs include prefabricated modular loops, advanced receivers employing 3-dimensional telecoils and intelligent loop amplifiers.

By addressing important, unmet needs of persons with and without hearing impairments, these technology solutions represent a significant business opportunity.

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Market

It is estimated that more than 20 million people in the United States experience some form of hearing loss.  Ninety to ninety-five percent of these people could benefit from hearing aids and assistive listening systems. A large majority of the people who would benefit from these devices (approximately 80%) have chosen not to use them. This leaves more than 16 million people with substantially correctable hearing loss who are not currently using assistive devices.  Many of the people in this population choose not to use the devices because they are not satisfied with the performance of products currently available or are reluctant to wear an obtrusive device they feel is stigmatizing.

Assistive Listening Systems (ALS) bring a remote (essentially 'noise free') sound into the direct-proximity of the user's ear in order to amplify a selected sound source, overcome background noise, enhance listening in large public venues, and improve one-to-one conversations. Used in combination with hearing aids an ALS can provide optimal sound clarity and speech comprehension. ALS are categorized by the wireless communication protocol used to link the remote sound source and the body-worn receiver. Common ALS include frequency modulated (FM), infrared (IR), and inductive loop (IL) systems. The receiver can be directly associated with the hearing aid (inbuilt FM receiver, FM-boot, telecoil). Alternatively, some IR and FM receivers retransmit the signal via an inductive neck loop to be picked up by the hearing aid telecoil.

According to the Hearing Aid Compatibility Act of 1988, all telephones sold in the US should be compatible with standard hearing aid telecoils. However, it is estimated that only 30% of modern hearing aids in the US actually incorporate a telecoil (National Center for Health Statistics, 1997). A telecoil is an induction coil placed in a hearing aid that is designed to pick up fluctuating magnetic fields produced by coils in the telephone hand set, so that these signals can be amplified without interference (Self Help for Hard of Hearing, 1999). Persons with greater hearing loss often have BTE hearing aids with T-coils, while persons with less severe hearing loss often have smaller ITC and CIC hearing aids that lack T-coils. As a consequence, persons with more severe hearing loss are more likely to benefit from inductive loop systems.

The Americans with Disabilities Act (ADA) and the Telecommunications Act have increased the popularity and availability of assistive technologies for employment, education, and access to buildings, transportation and telecommunications. The ADA requires that any business (auditoriums, theaters, etc.) with 50 or more fixed seats in an assembly area must make ALS available for at least 4% of the seating capacity (The US Equal Employment Opportunity Commission, 1990). The market potential for assistive listening systems is much broader than the hearing aid market. People without hearing impairments are currently using ALS for museum tours, nature walks, improved listening at philharmonic concerts, and other "enhanced listening experiences". Additionally, inductive loop technology used for high quality public address systems and for multi-channel, a multi-media entertainment venue poses a huge market opportunity for anyone able to develop these technologies.

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Current Technology

A generic inductive loop system consists of microphone, loop amplifier, wire loop and inductive receiver. A speaker talks into the microphone connected to the loop amplifier. The amplifier drives current into the wire loop wire placed around the reception area producing a time varying electromagnetic field. The electromagnetic field induces a current in the telecoil and the hearing aid transforms this signal into an acoustic output that is delivered to the ear. A microphone is the most common input device - but IL systems may also get their input from other sources (e.g. television SCART connection, special doorbells, telephone ringers, etc.) Large halls often have multiple microphone positions, and alternative sound sources such as tape machines and audio-mixing equipment interfaced to the system.

When properly installed, inductive loops systems are durable and simple to maintain. Common installation problems include the improper measurement of the loop area, incorrect measurement or calculation of field strength, and lack of knowledge of applicable standards. System performance is susceptible to changes in the environment (e.g. lighting, furnishings, room dimensions, etc.). Permanently installed inductive loops often require grooving the floor for cable placement and in some cases (e.g. historical sites, vinyl floor covering, etc.) this may be difficult, costly or impractical. To solve this problem, a flat insulated cable with adhesive backing has been developed and a plastic PVC cap can be placed over the cable for increased protection and durability.

Portable inductive loop systems are available for use with small groups of listeners and can be stored in a carrying case and set up as needed. Loop amplifiers must be properly matched to the load requirements of the inductive loop. Use of inappropriate amplifiers to drive the inductive loop results in poor performance and user dissatisfaction. For all practical inductive loop systems the inductive field can be picked up outside the looped area (a distance of perhaps 2 or 3 meters for a conventional loop). This effect is referred to as "signal spillover."

The 3D inductive loop systems use a special "loop processor" and "loop mats" rather than a single loop enclosing the reception area. The fields produced by a 3D-loop system substantially reduce the orientation dependency of a standard telecoil receiver. Field spillover for a 3D loop system is also substantially reduced relative to a conventional inductive loop system. Installing loop mats six feet apart essentially eliminates spillover. However, 3D mats may create distortion effects and cause dissatisfaction for persons with normal hearing. 3D-loop systems are much less common and generally more difficult to install than conventional loop systems.

The most common inductive receiver is the hearing aid telecoil. Built into a hearing aid, a telecoil is an inherently small and portable receiver. The sound level output from the hearing aid is dependent upon the field strength within the loop and the orientation of the receiver coil relative to the field. If the loop has been properly designed and installed, field strength should not vary greatly with the user's location within the loop. In principle, a field orthogonal to the coil plane will produce the largest signal (induced current) and a field parallel to the coil plane will produce no signal. Inductive receivers are not "tuned" - that is they do not support multiple communication channels and pick up "noise" from any magnetic field "in the room." The user must remain within the looped area in order to receive transmission. Voices simultaneously picked up through a hearing aid microphone and telecoil are sometimes difficult to comprehend. BTE hearing aids with 3-position T-switches (microphone only, T-coil only or both) mitigate this problem. Pocket, hand-held and ear level (similar in form to a hearing aid) receivers are also available. Sound from these devices is output through headphones (with or without a hearing aid in place) or earphones.

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Technology Requirements

Users, manufacturers, clinicians, researchers, and other stakeholders have identified technology that will significantly improve the performance of ALS and expand the market for inductive loop ALS and related technology.  Technology currently needed includes:

• Prefabricated modular loops (or mats)
• Advanced receivers employing 3-dimensional telecoils (or the equivalent)
• Intelligent loop amplifiers (or driver/adaptors for general purpose amplifiers)

The specific performance features for these technologies are listed below. Final product manufacturers and consumers are keenly interested in technologies that meet these needs. Both component and system solutions that enhance the lives of people with and without hearing disabilities present a significant business opportunity.^*

Inductive Loop System (Loop or analog, Amplifier and Receiver)

• Should be simple and foolproof for non-technical persons to install and operate (e.g. drop "loop" or "mat" onto floor; plug it into the amplifier; system senses and auto-adjusts field strength).
• Should produce high quality, undistorted sound from anywhere within the looped area (as perceived by a hearing aid user or non-hearing impaired person using a body-worn receiver and headphones).
• Should allow user to receive and select from a number of loops running in the same area (analogous to FM systems with multiple, selectable frequencies).
• Should have reliable and predictable performance.
• Might take advantage of signal spillover to configure for larger environments.
• Should be affordable for individuals, small businesses, organizations and community groups.

Loop (or analog)

• Should be prefabricated.
• Should be modular to allow for easy expansion.
• Should not be limited (in its applications) by room size, shape, architecture, etc.
• Should be durable.

"Loop" Amplifier

• Should have an intelligent driver/adaptor for general-purpose amplifiers.
• Should have field strength meter integrated into the inductive loop system that provides feedback to the amplifier (driver/adaptor).
• Should auto-adjust output based upon field strength.
• Should have tunable "frequency" (see Receivers below).
• Should imbed a "signal strength" reference signal (see Receivers below).

[Note: a "signal strength" reference signal might simplify the design of an "orientation insensitive" Receiver.]

Receivers (Hearing Aid and Body Worn)

• Should not be sensitive to the orientation of the inductive field (e.g. "3-dimensional" receiver that uses a microprocessor to process signals from two or three coils.)
• Should have the ability to distinguish loops by their "frequency."
• Should be able to tune into specific inductive loops.
• Should sense field strength and normalize sound output accordingly (e.g. a standard "amplitude" reference signal could be transmitted from the inductive loop).
• Should filter out common inductive noise (e.g. power - 60 Hz and harmonics).
• Should be shielded from high frequency interference.

Hearing Aid Receivers

• Should have programmable hearing aids with tunable receivers.
• Should fit in smaller hearing aids (ITE, ITC, CIC) used by persons with mild to moderate hearing loss.
• Should have improved sensitivity (e.g. increase coil size by embedding in hearing aid shell, changing core material, etc.).
• Should not significantly increase power consumption.
• Should have 3 settings (T-coil, microphone, both) for smaller hearing aids.
• Should have simple, easy to use T-coil controls.

Body Worn Receivers

• Should be "walkman style" and interface with (smaller) hearing aids by DAI.
• Should support headphones (or equivalent) for non-hearing impaired individuals.
• Should be comfortable (small size, reasonable weight, etc.) for when the user is physically active (e.g. dancing, aerobics, etc.)

^* Technology developers who are interested in Inductive Loop Technology solutions may also want to refer to the FM and Infrared Problem Statements. There may be opportunities to combine the technologies and leverage a multi-system solution for an expanded market share. New, innovative or revolutionary approaches that are independent of the technologies under consideration might provide the superior solution. Dr. Laszlo's comments introducing this section of the Proceedings are particularly relevant.

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References

National Center for Health Statistics. (1997). Advance Data ( 292). Washington, DC: Vital Statistics of the Centers for Disease Control and Prevention.

Self Help for Hard of Hearing, I. (1999). SHHH Position Statement: Telecoils. Available: http://www.odc.state.or.us/tadoc/hoh6.htm [April 25, 2000].

The US Equal Employment Opportunity Commission. (1990). Americans with Disabilities Act. Available: gopher://trace.wisc.edu/00/ftp/pub/text/ada_info/handbook/h_faq.txt [April 25, 2000]

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