Ear-canal wideband acoustic transfer functions of adults and two- to nine-month-old infants.
OBJECTIVE
Wideband acoustic transfer functions (WATF) measured in the ear canal have been shown to be effective in the diagnosis of middle ear dysfunction in adults and in newborn infants. Although these measures would be diagnostically useful in older infants, normative data on a large number of older infants are lacking. The goal of this study was to provide such normative data.


METHODS
The WATF of 458 infants aged 2 to 9 mos and of 210 adults were obtained. Wideband reactance (X), resistance (R), and energy reflectance (ER) were measured in third-octave bands between 250 and 8000 Hz. The effects of age and gender on the WATF were examined, and the WATF in the left and right ears were compared. Test-retest reliability was assessed, and the relationship between the 226-Hz tympanogram and the WATF was examined.


RESULTS
The results agreed well with previous reports testing fewer subjects, which documented age-related change in these measures during infancy and between infancy and adulthood. Test-retest correlations within third octaves were 0.5 to 0.7 at best, but did not vary systematically with age. Infants' test-retest absolute differences within third octaves for R and ER were similar to those of adults. The shape of the WATF on retest was highly repeatable, and the shapes of the WATF in the ears of the same individual were qualitatively similar. The wideband impedance results were not different in the left and right ears, but ER was slightly, but significantly, lower in the left ear than that in the right ear. Resistance and reactance magnitude were greater for females than males, but there was no effect of gender on ER. Infants whose 226-Hz tympanogram indicated reduced peak admittance (Types As and B) had greater resistance and reactance magnitude than those with normal peak admittance (Types A and C), but no tympanometry group differences were evident in ER.


CONCLUSIONS
Age-graded norms are essential to the successful clinical application of WATF. However, the effects of gender and laterality on the WATF are small.
Werner
Lynne A
LA
Department of Speech and Hearing Sciences, University of Washington, Seattle, Washington 98105-6246, USA. awerner@u.washington.edu
Levi
Ellen C
EC
Keefe
Douglas H
DH
D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D004424:Ear Canal / Q000502:physiology*; D004432:Ear, Middle / Q000502:physiology*; D005260:Female; D006311:Hearing Disorders / Q000175:diagnosis* / Q000503:physiopathology; D006320:Hearing Tests / Q000379:methods* / Q000592:standards*; D006801:Humans; D007223:Infant; D008297:Male; D011571:Psychoacoustics; D015203:Reproducibility of Results; D012737:Sex Factors; D055815:Young Adult