Fitting and Verification of Frequency Modulation Systems on Children with Normal Hearing
Authors: Schafer Erin C. , Bryant Danielle , Sanders Katie , Baldus Nicole , Algier Katherine , Lewis Audrey , Traber Jordan , Layden Paige , Amin Aneeqa 
Published: October 2014

Background:Several recent investigations support the use of frequency modulation (FM) systems in children with normal hearing and auditory processing or listening disorders such as those diagnosed with auditory processing disorders, autism spectrum disorders, attention-deficit
hyperactivity disorder, Friedreich ataxia, and dyslexia. The American Academy of Audiology (AAA) published suggested procedures, but these guidelines do not cite research evidence to support the validity of the recommended procedures for fitting and verifying nonoccluding open-ear FM systems
on children with normal hearing. Documenting the validity of these fitting procedures is critical to maximize the potential FM-system benefit in the abovementioned populations of children with normal hearing and those with auditory-listening problems.Purpose:The primary goal of this
investigation was to determine the validity of the AAA real-ear approach to fitting FM systems on children with normal hearing. The secondary goal of this study was to examine speech-recognition performance in noise and loudness ratings without and with FM systems in children with normal hearing
sensitivity.Research Design:A two-group, cross-sectional design was used in the present study.Study Sample:Twenty-six typically functioning children, ages 5‐12 yr, with normal hearing sensitivity participated in the study.Intervention:Participants used a nonoccluding
open-ear FM receiver during laboratory-based testing.Data Collection and Analysis:Participants completed three laboratory tests: (1) real-ear measures, (2) speech recognition performance in noise, and (3) loudness ratings. Four real-ear measures were conducted to (1) verify that measured
output met prescribed-gain targets across the 1000‐4000 Hz frequency range for speech stimuli, (2) confirm that the FM-receiver volume did not exceed predicted uncomfortable loudness levels, and (3 and 4) measure changes to the real-ear unaided response when placing the FM receiver
in the child’s ear. After completion of the fitting, speech recognition in noise at a ‐5 signal-to-noise ratio and loudness ratings at a +5 signal-to-noise ratio were measured in four conditions: (1) no FM system, (2) FM receiver on the right ear, (3) FM receiver on the left ear,
and (4) bilateral FM system.Results:The results of this study suggested that the slightly modified AAA real-ear measurement procedures resulted in a valid fitting of one FM system on children with normal hearing. On average, prescriptive targets were met for 1000, 2000, 3000, and 4000
Hz within 3 dB, and maximum output of the FM system never exceeded and was significantly lower than predicted uncomfortable loudness levels for the children. There was a minimal change in the real-ear unaided response when the open-ear FM receiver was placed into the ear. Use of the FM system
on one or both ears resulted in significantly better speech recognition in noise relative to a no-FM condition, and the unilateral and bilateral FM receivers resulted in a comfortably loud signal when listening in background noise.Conclusions:Real-ear measures are critical for obtaining
an appropriate fit of an FM system on children with normal hearing.