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Ear-Canal Wideband Acoustic Transfer Functions of Adults and Two- to Nine-Month-Old Infants

Werner, Lynne A.1; Levi, Ellen C.1; Keefe, Douglas H.2

doi: 10.1097/AUD.0b013e3181e0381d
Research Articles

Objectives: 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.

Design: 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.

New techniques for measuring the response of the external and middle ear have the potential to improve screening and diagnosis of conductive disorders in infants. These techniques are referred to as wideband acoustic transfer functions (WATF). A limitation of WATF is that norms for infants more than a few days old are not currently available. This paper reports WATF for adults and for infants between two and nine months of age. Effects of age, gender, and laterality were identified. The reliability of measurement as well as the relationship between the WATF and tympanometry outcome were also assessed. SUPPLEMENTAL DIGITAL CONTENT IS AVAILABLE IN THE TEXT.

1Department of Speech and Hearing Sciences, University of Washington, Seattle, Washington; and 2Boys Town National Research Hospital, Omaha, Nebraska.

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Address for correspondence: Lynne A. Werner, Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd Street, Seattle, WA 98105-6246. E-mail:

Received September 15, 2009; accepted March 2, 2010.

© 2010 Lippincott Williams & Wilkins, Inc.