Fitting and verification of frequency modulation systems on children with normal hearing.

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 The American Academy of Audiology (AAA) published suggested procedures, but these guidelines do not cite research evidence to support the validity of the recommended procedures for fitting and verifying nonoccluding open-ear FM systems on children with normal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 above-mentioned 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.

Developmental effects and spatial hearing in young children with normal-hearing sensitivity.

OBJECTIVES: Previous research suggests that young children have significant difficulty recognizing speech in the presence of background noise as compared with older children and adults. However, limited research exists that examines the developmental effects of speech recognition in noise in separate age groups of young children, especially in a classroom setting. The lack of research may relate to the limited number of tests with multiple, equally intelligible lists in noise that are also appropriate for young children. As a result, the goals of the present study include investigating (1) effects of age and (2) benefits of spatial separation of speech and noise sources on the speech recognition in noise performance of young children with normal-hearing sensitivity. A secondary goal of the study was to establish the validity and reliability of the Phrases in Noise Test (PINT) for assessing the 50% correct speech-in-noise threshold of young children. DESIGN: The investigators used a two-way repeated measures design to examine the main effects of age and spatial separation. Sixty-eight children in separate groups of 3-, 4-, 5-, and 6-year-olds and 17 adults completed two speech-recognition conditions with (1) speech and noise from the same loudspeaker at 0-degree azimuth (S0/N0) and (2) speech and noise from separate loudspeakers at 0- and 180-degree azimuth (S0/N180). Recruiting sites included local preschools and school districts for children and a university for adults. RESULTS: The results of this investigation suggest that younger children (<4 years of age) have significantly poorer speech-in-noise thresholds than older children and adults, and 4- and 5-year-old children also have significantly poorer performance than adults when speech and noise are presented from the same spatial location. All participants obtained significant spatial release from masking. On a parent and teacher screening questionnaire to assess educational risk, five of 12 children with at-risk behaviors had poor speech-in-noise thresholds relative to their peers. When two lists of the PINT are used, the test seems to be a valid and reliable measure for assessing young children's speech-in-noise thresholds. CONCLUSIONS: Young children exhibit significantly poorer speech recognition than do older children and adults in a classroom, especially when speech and noise are presented from the same location. Given the poor acoustics of typical classrooms, and the earlier age at which many children are educated, special modifications to classrooms may be necessary to improve listening through acoustic modifications or classroom amplification. A combination of a parent or teacher questionnaire and the PINT may be helpful in identifying children who are at risk for educational delays and listening difficulties in classrooms with typically poor acoustics.