Forum Proceedings

Summary

Manufacturers, researchers, consumers and other stakeholders have identified a "universal" Personal Communication Systems as a high priority technology need.  As defined, the system is extremely flexible. It can benefit people with any degree of hearing loss (from persons with no hearing loss to persons with severe hearing impairments) across a wide range of applications and environments. For example - the Portable Transmitter and Portable Repeater would be extremely useful devices even if purchased separately. As with any body-worn device, the manufactured product must pay careful attention to cosmetic issues (size, weight, appearance, etc.) and cost.  Enhanced technologies for portable transmitters, repeaters, and receivers were identified as critical for improving FM systems.

Universal solutions in the field of FM ALS will have broad applications in consumer products such as cell phones, stereos, televisions, audio mixers and computers.  By addressing important, unmet needs of people both 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. (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, FM technology used for high quality public address systems and for a multi-channel, multi-media entertainment venue poses a huge market opportunity for anyone able to develop these technologies.

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Current Technology

FM systems provide a personal communication channel between the speaker and the listener that shortens the "acoustical pathway" between speaker and listener and improves the signal-to-noise ratio. Personal FM systems are available for one-on-one (single speaker / single listener) communication and wide area FM systems are available for one-to-many (single speaker / many listeners) communication. Systems are currently not available for many-to-many (natural, small group) communication. FM systems are used in most environments (e.g. classrooms, museums etc.) generally excepting those environments where they can interfere with electronic or telecommunications equipment (e.g. hospitals, airplanes).

FM systems transmit in two, non-reserved portions of the frequency spectrum - 72 MHz to 75 MHz and 216 MHz to 217 MHz. FM systems are susceptible to interference from other radio sources (e.g. pagers, emergency vehicles) especially at lower frequencies (72 MHz -76 MHz) and electromagnetic interference (e.g. motors, computers, lightning controls, power strips, etc). Building structural elements can cause multi-path interference and signal dropout.  FM systems typically use non-overlapping 50 kHz bands (referred to as 'narrow band transmission'), or 150 kHz / 200 kHz bands (referred to as 'broad band transmission'). Federal Communication Commission regulations limit the permitted maximum power of the transmitted signal. FM system transmitters are generally omni-directional and have a typical range of 300 to 500 feet (at 72 MHz to 75 MHz). Range can be increased by using a larger antenna or by transmitting at higher frequencies (216 MHz to 217 MHz). Some FM systems are multi-frequency with as many as 50 narrow band channels or 10 wide band channels. Multi-frequency systems support simultaneous, non-interfering communication within the same environment. FM transmissions cannot easily be confined to a "room" and anyone with an appropriate receiver can "listen in."

Large Area FM Systems are used to enhance one-to-many communication. The most common input device is a single microphone, but multiple microphones, remote microphones and alternative sound sources (e.g. tape machines, audio-mixing tables, etc.) may also provide the input. Many large area FM systems provide a range of input pre-processing options. It is unclear whether such preprocessing, coupled with the customized signal processing provided by each listeners' hearing aid will generally improve signal clarity or speech comprehension. The dynamic range of input signals can be quite large and some form of input compression will often be necessary to avoid saturating signal output while still maintaining audibility at low input levels.

Personal FM systems are used to enhance one-to-one communication. The speaker wears a microphone and portable FM transmitter while the listener wears a portable receiver. Both the speaker and listener can move about.

Sound-Field Systems are essentially a Public Address system whose input device is a wireless microphone. The speaker talks into the FM microphone/transmitter that transforms and broadcasts the signal to an FM receiver/amplifier connected to, or physically located within, a loudspeaker. This system is used to amplify the speaker's voice so that it is clearly audible above background noise.

Wireless headphones (FM or IR) are gaining acceptance for home entertainment (e.g., TV, music, etc.) where a person needs a volume level that would disturb others. The transmitter receives its input from an audio jack (television, radio, etc.) or from a microphone placed near the sound source. The receiver is built into the headphone.

FM hearing aid receivers are built into or an accessory (e.g. FM-boot) to larger hearing aids (e.g. "behind-the-ear" BTE) but are not accommodated by smaller aids (e.g. "in-the-canal" ITC and "completely-in-the-canal" CIC). FM hearing aid receivers are generally small and inconspicuous with the possible exception of the antenna. There has been some discussion about adopting a standard modular FM receiver (FM boot) but it may be difficult to make these receivers fully compatible across makes and models of hearing aids. FM hearing aid receivers (built in or boot) draw power from the hearing aid battery, decreasing battery life.

Portable FM Transmitters currently have an in-built microphone. There is also a provision to have an external audio line input. The antenna is built into the transmitter (e.g. the stand is also an antenna on some transmitters). Most portable transmitters are capable of channel adjustments. The range of portable transmitters is generally up to 100ft. While some small FM transmitters exist (down to 3.5 oz), many of current transmitters are too large to be used while performing severe physical activities like dancing, aerobics, etc. Portable FM transmitters generally use rechargeable batteries (6-10 hrs of continuous use between charges typical or disposable batteries (15-60 hours between replacement is typical).

Portable FM receivers are completely separate from the hearing aid. These receivers (commonly) support headphones and inductive neck loops, silhouettes or DAI connections for hearing aid users.  Multi-frequency receivers don't signal the user when the transmission is lost or the carrier frequency has been switched at the transmitter. The receivers also do not go to "low-power standby" if the carrier frequency is not detected. Frequency selection is manual and users often find it difficult to select the correct frequency. Portable FM receivers generally use rechargeable batteries (6-10 hours of continuous use between charges typical) or disposable batteries (18-70 hours between replacement typical). The systems require administration - batteries must be charged or replaced and receiver hygiene maintained (especially for large area system receivers).

Hearing Aids with a bi-directional communication link and appropriate processing capabilities can act together as beam-forming microphone arrays. Binaural hearing aids use the increased separation between microphones, head shadow effects and time and phase delays to mimic the capabilities of an intact hearing system. Binaural processing requires a bi-directional communication link between the two hearing aids. A product appeared briefly on the market that employed an AM wireless link between the two hearing aids. An advanced binaural hearing aid prototype was recently developed that hard-wired the two "hearing aids" to an external digital signal-processing unit. It was reported that this prototype provided 17 dB of directional gain (Kompis, 2000).

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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 FM ALS and related technology. Technology currently needed includes:

• Standardized personal communication systems
• Portable transmitters
• Portable repeaters
• Portable receivers

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.

Personal Communication System.^*

• Should consist of a Transmitter, a Body-Worn Repeater and a Hearing Aid Receiver.
• Should have components that can be used separately or as part of the system.
• Should have components that are not be obtrusive (should be small and/or cosmetically attractive)
• Should benefit people with any degree of hearing loss (from no hearing loss to severe hearing impairments).
• Should guarantee privacy and security.
• Should provide a clear, undistorted sound (e.g. consider a person with unimpaired hearing at a cello concert.).
• Communication protocols other than FM should be considered - including universally accepted wireless standards.

Portable Transmitter

Critical Features

• Should have bi-directional wireless link between Transmitter and Repeater.
• Should have adjustable transmission range of 0 - 40 meters between Transmitter and Repeater.
• Should accept input from a wide array of consumer and telecom devices (telephones; alert systems; doorbells; television, radio, computer audio jack; audio mixers, etc.).

Other Features

• Should be size of fountain pen to size of cigarette pack and weigh 4-5 ounces.
• Should have controls that: are large (require low precision); provide tactile feedback (switch function identifiable by touch); watertight (e.g. sealed membrane)
• Should have "UP / DOWN switch" for manual frequency selection.
• Should provide feedback (e.g. steady or blinking LED) when active.
• Should have mute option (carrier maintained but no sound signal transmitted).
• Should have unbreakable antenna that is inside of the transmitter or can be "folded out" so the transmitter can be "stood up on the table."
• Should have jack for optional 4" external antenna (increase range).
• Should have 15 to 20 hours between battery recharge.
• Should have power level indicator.
• Should have automatic power down when not in use.

Portable Repeater

Critical Features

• Should have the same communication capabilities as the Transmitter (e.g. omni-directional transmission, bi-directional handshaking with transmitter, range, etc.).
• Should work with all Personal and Large Area FM Transmitters already in the market (Note: Repeater would not use bi-directional capability in this case.)
• Should work with all hearing aids (interface through FM Receivers, T-coils or DAI) already in the market.
• Should accept microphone input.
• Should have universal input capabilities (e.g. computers, television, radio, etc.)
• Should have universal output capabilities (e.g. headphones, tape recorders, public address systems, audio mixers, headphones etc.)

Other Features

• Should be frequency agile (automatically "scan" and "lock onto" the Transmitter frequency)
• Should select "last Transmitter frequency used" when turned ON.
• Should provide feedback to the user when the Transmitter carrier is detected or lost.
• Should have manual UP/DOWN switch for Transmitter frequency selection (e.g. for multi-frequency environments such as theatres).
• Should have manual volume control.
• Should have active tone control and active high frequency gain.
• Should have ON/OFF indicator (e.g. LED)
• Should have power level indicator.
• Should have batteries that last 3-4 weeks at 8-10 hours of continuous use OR disposable batteries with a minimum operating life of 40 hours. Batteries should be recyclable.
• Should be watertight (e.g. sealed membrane switches)
• Should be about the same size as the Personal FM System Transmitter.
• Should have a microphone that is detachable from the Transmitter; is "swappable" - you can switch between microphones with different functional characteristics; and can be nested into one end of the transmitter. This microphone should pick up speech in noise sensitivity without saturation) and quiet speech in a quiet environment; be highly directional - capable of picking up sound signal (voice) at 8 to 10 feet in a noisy environment (a directivity pattern of 20 - 40 degrees); and "switchable" between omni-directional and directional modes. Advanced characteristics (adapts directional response in noise, orients to speaker, etc.) should be considered. Microphone should be durable (water, wind - disposable wind screen, and shock resistant) with low sensitivity to vibration

Portable Receiver

Critical Features

• Should have one-way wireless link from Repeater to Hearing Aid Receiver - link through inductive loop or DAI is less ideal.
• Should pick up and lock onto the Repeater signal (e.g. smart signal detection, select strongest signal, etc.)
• Should be built into Hearing Aid - accessory similar to a FM boot is less ideal.

Other Features

• Should weigh about the same as an FM boot (if integral to the hearing aid)
• Should have reliable electronic interface between Receiver (FM boot like accessory) and Hearing Aid (e.g. durable, waterproof, etc).
• Should have internal antenna.
• Should NOT have visual indicators (e.g. power level, signal detect, etc).
• Should have non-visual, low battery indicator (e.g. tone, vibrate)
• Should have easy to use, manual ON/OFF switch.
• Should be powered off of hearing aid battery.
• Should have battery that sources > 3-4 milliamps current.
• Should have battery that is easy to replace.
• Should be rechargeable battery with 12 hours time-between-recharge.
• Should be moisture resistant and durable (unbreakable)
• Should use batteries with reduced size, increased time between recharge, increased capacity, reasonable cost etc.

^* Note: Technology developers who are interested in FM solutions may also want to refer to the Infrared and Inductive Loop 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

Kompis, M. (2000). A Combined Fixed/Adaptive Beamforming Hoise-Reduction System for Hearing Aids. IEEE. Available: http://www.orlinsel.ch/research/htm [April 25, 2000].

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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