International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A composite PCM/FM+FM/FM system combines the spectral efficiency of the analog system with the accuracy of a PCM system when needed for specific sensors and allows the direct transmission of binary computer words if necessary. A PCM/FM+FM/FM system combines the bit sequence with the modulated subcarriers at baseband and the resultant modulates the carrier. In the design of the composite system it is of importance to determine the impact of the subcarriers on the bit error rate of the bit sequence and to determine the degradation of the output signal-to-noise ratio of the subcarrier channels caused by the bit sequence.

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Aims: The aims of this study were to identify school-aged children who exhibit spatial stream segregation deficits by using the Listening in Spatialized Noise – Sentences (LiSN-S) test, and to determine the effectiveness of personal FM systems as an intervention for these children. Method: Participants consisted of 22 children between the age of 7;0 and 11;11 years with normal hearing thresholds. Based on their performance on the LiSN-S test, participants with normal and impaired spatial stream segregation ability were assigned to the control group (n=12) and the FM group (n=10) respectively. Participants from the latter group were provided with and required to use the personal ear-level FM devices during school time for a period of eight weeks. The impact of the FM systems was determined by both quantitative and qualitative data, which were gathered at three sampling points: (1) Before FM trial; (2) At the end of the FM trial (i.e. after eight weeks of use); and finally (3) At eight weeks following withdrawal of the FM systems. Results: Results revealed children with APD improved on their ability to segregate spatial streams following the use of personal FM devices, whereas control participants did not exhibit this change. The personal FM devices seemed to provide the greatest benefit to the younger participants. Qualitative measures, including individualised Goal Attainment Scales (GAS), indicated positive improvements in auditory behaviours following the use of FM devices in all participants. In addition, teachers anecdotally reported positive behavioural changes in the FM participants during the FM trial. Conclusion: Personal FM systems appear to be an effective management strategy for school age children who exhibit difficulty in spatial stream segregation.

The two objectives of this single-subject study were to assess how an FM system use impacts parent-child interaction in a noisy listening environment, and how a parent/caregiver training affect the interaction between parent/caregiver and child. Two 5-year-old children with hearing loss and their parent/caregiver participated. Experiement 1 was conducted using an alternating design measured three communication behaviors (e.g., child's vocalization, parent/caregiver's initiation, and parent/caregiver's response) across four listening conditions (e.g., HA+Quiet, HA+Noise, FM+Quiet, and FM+Noise). Experiment 2 was conducted using a comparison within and between conditions to re-measure the communicative behaviors across the listening conditions after the parent/caregiver training. Findings of this study point to three major conclusions. First, FM system use (i.e., FM-only mode) facilitated FM01 child's ability to maintain same level of interaction in a noisy as good as in a quiet environment. Second, parent/caregiver training enhanced the impact of FM system use for one child (FM01), although parent/caregiver initiation increased for both. Third, it is important to verify the function of both FM system and HA microphones to ensure access to FM advantage.

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