Digital Wireless Telephones and Hearing Aids: An Introduction
Millions of people are using cellular telephones ("cell phones") because of the convenience and safety that mobile, wireless communication provides. Some people are even switching completely to wireless communications, giving up entirely their use of fixed wireline/wired telephones. And, like many other forms of technology, cellular telephones are making a technical migration from an analog implementation to a digital implementation. Unfortunately, with the introduction of digital technologies for wireless communication in the mid-1990s, and now the limited availability of analog service, many hearing aid wearers have found it difficult if not impossible to take advantage of the benefits offered by this fast-growing industry.
Nature of the Problem
Digital wireless telephones are incompatible with many hearing aids due to the potential for radio frequency (RF) interference from the cell phone, regardless of whether acoustic or inductive (“t switch”) hearing aid coupling is used. When a wireless phone is in communication with its network, an electromagnetic field is present around the phone’s antenna. During communication over a digital wireless phone this field pulses. It is this pulsing energy that may be picked up by the hearing aid’s microphone or telecoil circuitry and heard as a buzzing sound (i.e., interference) through the wearer's hearing aid.
In addition to this problem of RF incompatibility, cell phones are currently exempt from the legal requirements for hearing aid compatibility (i.e., capable of coupling inductively to a hearing aid telecoil.) and volume control placed on corded and cordless phones. Based on pressure from consumer groups, the FCC is reviewing the exemption for cell phones at this time (2002).
Options for Using a Digital Wireless Telephone
RF interference does not occur for all combinations of digital wireless telephones and hearing aids. However, when interference does occur, the buzzing sound can make speech understanding difficult, communication over cell phones annoying, and in the most severe cases, render the phone completely unusable to the hearing aid wearer. For hearing aid wearers who want to use a digital wireless telephone, there are a number of options.
The first option is try to locate a service provider that uses a technology called CDMA, which produces less bothersome interference than other digital wireless technologies. Currently CDMA is the technology used by Verizon Wireless and Sprint PCS. Another technology that is relatively mild in interference is iDEN, used by NexTel.
If possible, the consumer should try a wireless phone of the "clamshell" style. This style has a flip-down cover with the speaker in the flip part of the phone and the rest of the handset electronics in the base of the phone. (However, other handsets may work well with the hearing aid, particularly if the service provider uses CDMA.)
If this does not work and audible interference remains a problem, it may be necessary to use an accessory. An accessory places distance between the phone and the hearing aid, thereby reducing or eliminating electromagnetic interference.
Some wireless telephone service providers, handset manufacturers, and third-party vendors are providing hearing aid compatible (HAC) accessories for people using telecoils in their hearing aids. These accessories include compatible inductive neckloops, inductive silhouettes, and direct-audio-input-modified earbuds, each with built-in microphones for hands-free phone use. Neckloops, also called loopsets, are unobtrusive accessories that plug into compatible phones. Loopsets include a built-in microphone and permit hands-free use of the phone and binaural listening if the user has two hearing aids with telecoils. The phone itself can be carried in a pocket or clipped on a piece of clothing, away from the hearing aids.
For individuals in the market for new hearing aids, manufacturers are working to increase hearing aid immunity to electromagnetic interference through shielding and circuit modification and design. Some manufacturers have marketed products advertised with this characteristic. Consumers should be sure to ask their audiologist or other hearing aid dispenser to inform you about immunity to interference, including cell phone interference.
The American National Standards Institute (ANSI) has developed a standard addressing the compatibility problem between digital wireless telephones and hearing aids. The standard categorizes both phones and hearing aids based on the independent measurement of each device. Each telephone and hearing aid category has a corresponding number. When the number for a given telephone and the number for a given hearing aid are added together, the resulting number will provide a prediction of the expected level of performance (the interference generated) by that combination of telephone and hearing aid. Compliance with the standard is voluntary with no provision for product labeling on the part of hearing aid or telephone manufacturers. To date, information regarding a product’s category number is not readily available for consumers to use in their decision making process.
There a number of ways hearing aid wearers can advocate for themselves regarding this issue. They can provide feedback to the industry, hearing healthcare professionals and government agencies regarding their experiences with digital wireless telephones. Within the cellular telecommunications industry, individuals can contact the disability access personnel at companies providing their cellular service and their wireless phone. Within the hearing aid industry, consumers can contact their audiologist and the company that manufactured their hearing aid(s). Within the Federal Communications Commission (FCC), individuals can contact the Consumer and Governmental Affairs Bureau.
The problem of digital wireless telephone interference with hearing aids continues to be a difficult one. While progress in mitigating this problem has been made, the complexity and changing nature of service and products will likely complicate the hearing aid wearers' challenge in understanding and managing this potential problem for the foreseeable future
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