The importance of early identification and appropriate audiologic management of children with hearing impairment is well known. In order to achieve optimal use of residual hearing for the development of speech and language, a consistent and nondistorted auditory signal is necessary. The major goal in fitting amplification is to improve the signal-to-noise ratio (S/N) in order to increase the understanding of speech.
Unfortunately, the ability of personal amplification (i.e., a hearing aid) to provide an optimal speech signal to the hearing-impaired child is compromised by acoustic conditions commonly encountered in various listening environments. Speaker-to-listener distance, background noise, and reverberant room characteristics combine, resulting in a deterioration in speech recognition ability in hearing-impaired listeners regardless of age.
Very young children experience language under a variety of acoustic conditions. Typically, an infant or toddler receives close, one-to-one attention from the parent or caregiver with abundant opportunities for communicative interaction. Exposure to incidental speech that occurs naturally in the home is also critical for normal speech and language development. This incidental speech does not necessarily occur in quiet nor with the infant nearby. In addition, with the rise in the use of day-care facilities, infants and toddlers may frequently encounter listening environments less suitable than the ideal, one-to-one situation. Similar acoustic conditions are known to be completely unsuitable for school-aged children with hearing impairments.
FM amplification systems have been designed to provide a solution for deleterious acoustic circumstances that listeners with hearing impairment encounter at home, in the classroom, or in many other common listening environments. The significant advantage of FM amplification over personal hearing aids has been documented for school-aged children with hearing impairments. In principle, FM listening allows a constant distance of approximately 6–8 inches to be maintained between the speaker's lips and the FM transmitter microphone. Thus, a greatly enhanced S/N is provided regardless of the distance between the child and the speaker or the acoustic environment.
In the past, FM systems have been used separately from the personal hearing aid and primarily in a formal classroom environment. Technological improvements currently allow the FM system to be coupled to the child's personal hearing aids. This provides the advantages of FM transmission while, in theory, maintaining the electroacoustic characteristics of the child's own hearing aid. These systems are also well suited for use in less structured environments.
Public Law 99-457 expands identification and education of disabled infants and toddlers, including those with hearing impairments. Appropriate audiological management for these children must include selection and fitting of suitable amplification for all listening environments. Personal hearing aids may be appropriate for some communication situations, but the use of FM amplification may be necessary in others. It is incumbent on professionals providing services to young children with hearing impairment to provide optimum amplification during the early years of life—the most critical period for speech and language development.