The use of frequency-modulated (FM) systems with cochlear implants has steadily increased as the FM technology has become more integrated with the cochlear implant speech processor and as research continues to show significant benefits in speech recognition in noise. The FM system should no longer be considered an optional accessory to the cochlear implant speech processor, but rather as one of the basic components. To support this premise, the use of FM systems with cochlear implants will be addressed through five key questions.
1. What are FM systems?
An FM system consists of a transmitter with a microphone worn by the speaker and a receiver worn by the listener. The transmitter microphone options today include boom and lapel styles, as well as directional and noise reduction options, all of which add to the increased signal-to-noise ratio for the cochlear implant user. The FM receiver ranges from an integrated unit with the behind-the-ear cochlear implant speech processor to a body-worn small cube connected to the processor via a cord. The arrangement will depend on the options offered by the cochlear implant manufacturer. Visit www.utdallas.edu/~thib/ASHACIFMHandout.doc for a review of coupling options.
2. Why should FM systems be used?
The benefits of improving the signal-to-noise ratio by providing a remote microphone that transmits directly to the cochlear implant user are well documented (Anderson, Goldstein, Colodzin, & Iglehart, 2005; Davies, Yellon, & Purdy, 2001; Schafer & Thibodeau, 2003, in press). Although noise-reduction technology is incorporated into cochlear implants, this technology cannot compensate for the reduction in the speech signal that occurs as the distance from the speaker is increased. Technology that can increase speech recognition in noise by an average of 30% (Thibodeau et al., 2005) or can maintain performance with a 16 dB increase in noise (Schafer & Thibodeau, in press) has certainly gained recognition as more than an accessory item.
3. Who should use it?
The premise of employing FM systems as a standard feature rather than as an accessory implies that it is appropriate for all cochlear implant users. Certainly adults and older children would be able to control the use of the FM system. However, there are some concerns that young children with limited language may not be able to reliably report the integrity of the signal; therefore, use of FM systems should be reserved only for older children. The functioning of the cochlear implant on a young child with limited language can only be confirmed by the child's behavioral response. After the FM components have been verified independently of the cochlear implant (Thibodeau, 2006), the same techniques used to verify that the cochlear implant alone is functioning on a young child can be used to verify that the cochlear implant and FM system are functioning together.
4. Where should it be used?
The use of FM systems with cochlear implants is most often addressed in educational environments in which the noise level may interfere with learning new information. However, there are many additional possibilities for FM use that may have positive impacts in addition to improved speech recognition. When the cochlear implant user asks a group leader to wear the FM microphone, whether in a Girl Scout or city council meeting, they are letting others know the importance of good communication and displaying a positive model of self-advocacy. When parents wear the FM transmitter at home, despite relatively quiet environments, they report increased vocalizations for themselves and their children (Thibodeau & Schafer, 2002). Furthermore, when FM systems are worn in public, they provides a strong message that the technology is helpful and not something to hide. Of course, inappropriate use of the FM system should be avoided, such as using the system as a remote communication device when the speaker and listener are not visible to each other.
5. When should it be used?
If research supports significant speech recognition benefits when using an FM system with a cochlear implant, then shouldn't it always be used? The answer is definitely not! Because listeners often are not in complete control of their acoustic environments or the speakers who wear the FM microphones, they must be prepared to listen in challenging situations. Cochlear implant users need to continue to develop listening skills in noisy environments, analogous to an athlete who includes incline training as part of preparing for a race.
However, when learning new information, the increased signal-to-noise ratio provided by the FM system allows the cochlear implant user to focus on the new information without dividing cognitive resources with auditory processing in noise. Adult cochlear implant users will evaluate the acoustic situation to determine when to use the FM system, weighing the stress of listening in noise versus the importance of the communication.
The research evidence supports the use of FM systems with cochlear implants to achieve significant benefits in speech recognition. The inability to listen to the signal when verifying FM systems, as is traditionally done when combining hearing aids with FM systems, should not be a deterrent in fitting these systems because there are numerous ways to verify FM components prior to connection to the cochlear implant (Thibodeau, 2006). The audiologist, teacher, and/or caregiver will need to continue routine informal verification of the cochlear implant and FM combination, similar to the verification typically done when wearing a cochlear implant alone. The FM system is most important in situations involving learning new information or listening in challenging acoustic environments; however, it should not be used exclusively, so that the cochlear implant user may become adept at listening in a variety of acoustic environments.