infrared transmission. The receiver routes the signal to the hearing aid (or other amplifier), from which it is delivered to the listener. A related category of ALDs converts the acoustic speech signal into a visual representation. Examples of these are real-time captioning and speech recognition technology such as that used by CapTel. There are also other visually based technologies such as TTY (a keyboard and display device connected to the phone system), e-mail, and instant messaging.
Alerting ALDs are designed to improve detection of warning and alerting signals by substituting visual or vibratory signals for auditory signals. Examples of this category include vibrating alarm clocks, light-up telephone signalers, and doorbells and fire alarms that activate flashing lights.
ALDs are often considered appropriate in addition to a conventional hearing aid or in cases in which a hearing aid is not effective or desired. Despite enthusiastic support from some professionals (e.g., Loovis, Schall, and Teter, 1997) and considerable popularity in some other countries, ALDs are not used very much in the United States (with the exception of amplified telephones). It is not clear whether this results from a culturally based reluctance to embrace devices that are more obvious, or whether it results more from lack of their promotion by hearing care professionals.
Although both alerting and acoustic ALDs seem to be used quite effectively in some home situations, their penetration into work settings and other settings outside the home is reported to be limited (Bowe, 2002; Kochkin, 2002; Wheeler-Scruggs, 2002). The reasons for this are not clearly established. Reluctance of workers to request accommodations may be a contributing factor; lack of knowledge about available and appropriate devices is another.
In addition, there is evidence that persons with hearing loss are often reluctant to utilize ALDs that they know to be helpful because they are conspicuous and potentially stigmatizing. For example, with a personal FM system, the talker must be close to the microphone (typically holding it or wearing it) before the device will be helpful to the listener with the hearing loss. It is difficult to achieve this in an inconspicuous, flexible manner that does not inconvenience communication partners in the work setting.
This presumption has been supported in two studies that have compared hearing aids and ALDs in fairly large groups of persons with hearing loss. Jerger et al. (1996) noted that although many subjects preferred the sound quality of an ALD (a personal FM system), 97 percent of them still preferred to use a conventional hearing aid in daily life. Yueh et al. (2001) reported that use of conventional hearing aids produced substantial reported improvements in hearing-related quality of life, whereas the