Recent studies with adults have suggested that amplification at 4 kHz and above fails to improve speech recognition and may even degrade performance when high-frequency thresholds exceed 50-60 dB HL. This study examined the extent to which high frequencies can provide useful information for fricative perception for normal-hearing and hearing-impaired children and adults. Eighty subjects (20 per group) participated. Nonsense syllables containing the phonemes /s/, /f/, and /O/, produced by a male, female, and child talker, were low-pass filtered at 2, 3, 4, 5, 6, and 9 kHz. Frequency shaping was provided for the hearing-impaired subjects only. Results revealed significant differences in recognition between the four groups of subjects. Specifically, both groups of children performed more poorly than their adult counterparts at similar bandwidths. Likewise, both hearing-impaired groups performed more poorly than their normal-hearing counterparts. In addition, significant talker effects for /s/ were observed. For the male talker, optimum performance was reached at a bandwidth of approximately 4-5 kHz, whereas optimum performance for the female and child talkers did not occur until a bandwidth of 9 kHz.
Objective
Universal newborn hearing screening (UNHS) test outcomes can be influenced by conditions affecting the sound-conduction pathway including ear-canal and/or middle-ear function. The purpose of this study was to evaluate the test performance of wideband (WB) acoustic transfer functions (ATFs) and 1-kHz tympanometry in terms of their ability to predict the status of the sound-conduction pathway for ears that passed or were referred in a UNHS program.
Design
A distortion-product otoacoustic emission (DPOAE) test was used to determine the UNHS status of 455 infant ears (375 passed and 80 referred). WB and 1-kHz tests were performed immediately following the infant s first DPOAE test (Day 1). Of the 80 infants referred on Day 1, 67 infants were evaluated again following a second UNHS DPOAE test the next day (Day 2). WB data were acquired under ambient and tympanometric (pressurized) ear-canal conditions. Clinical decision theory analysis was used to assess the test performance of WB and 1-kHz tests in terms of their ability to classify ears that passed or referred, using DPOAE UNHS test outcomes as the “gold standard”. Specifically, for 1-kHz tympanometry, performance was assessed using previously published measurement criteria and for WB measurements, performance was assessed using a maximum-likelihood procedure.
Results
For measurements from Day 1, the highest area under the receiver operating characteristic (AROC) curve was 0.87 for an ambient WB test predictor. The highest AROC among several variables derived from 1-kHz tympanometry was 0.75. In general, ears that passed the DPOAE UNHS test had higher energy absorbance compared to those that referred, indicating that infants who passed the DPOAE UNHS had a more acoustically efficient conductive pathway.
Conclusions
Results showed that: 1) WB tests had better performance in classifying UNHS DPOAE outcomes than 1-kHz tympanometry, 2) WB tests provide data to suggest that many UNHS referrals are a consequence of transient conditions affecting the sound-conduction pathway, 3) WB data reveal changes in sound conduction during the first 2 days of life, and 4) WB measurements used in the present study are objective and quick, making these tests feasible for potential use in conjunction with UNHS programs.
Results suggest that early-identified children are delayed in consonant and syllable structure development, which may influence early word learning rates. Fricative/affricate development appears to be challenging for some infants with hearing loss. This may be related to the effects of sensorineural hearing loss on high-frequency information, restricted bandwidth provided by amplification, and reduced audibility in contexts of noise and reverberation. Delayed fricative use may have implications for morphological development. Atypically slow rates of change in syllable development may indicate that a child is at risk for delayed speech development.
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