title: Procedures for ambient-pressure and tympanometric tests of aural acoustic reflectance and admittance in human infants and adults.
abstract: Procedures are described to measure acoustic reflectance and admittance in human adult and infant ears at frequencies from 0.2 to 8 kHz. Transfer functions were measured at ambient pressure in the ear canal, and as down- or up-swept tympanograms. Acoustically estimated ear-canal area was used to calculate ear reflectance, which was parameterized by absorbance and group delay over all frequencies (and pressures), with substantial data reduction for tympanograms. Admittance measured at the probe tip in adults was transformed into an equivalent admittance at the eardrum using a transmission-line model for an ear canal with specified area and ear-canal length. Ear-canal length was estimated from group delay around the frequency above 2 kHz of minimum absorbance. Illustrative measurements in ears with normal function are described for an adult, and two infants at 1 month of age with normal hearing and a conductive hearing loss. The sensitivity of this equivalent eardrum admittance was calculated for varying estimates of area and length. Infant-ear patterns of absorbance peaks aligned in frequency with dips in group delay were explained by a model of resonant canal-wall mobility. Procedures will be applied in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function.
authors.affiliation: Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Keefe
authors.affiliation: Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA.
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Hunter
authors.affiliation: National Center for Rehabilitative Auditory Research, VA Portland Health Care System, 3710 SW US Veterans Hospital Road, Portland, Oregon 97239, USA.
authors.forename: M Patrick
authors.initials: MP
authors.lastname: Feeney
authors.affiliation: Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
authors.forename: Denis F
authors.initials: DF
authors.lastname: Fitzpatrick
mesh_terms: D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation; D000162:Acoustics; D000328:Adult; D000367:Age Factors; D000399:Air Pressure; D004424:Ear Canal / Q000033:anatomy & histology / Q000502:physiology*; D006309:Hearing; D006314:Hearing Loss, Conductive / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007223:Infant; D008297:Male; D008954:Models, Biological; D009038:Motion; D011237:Predictive Value of Tests; D011312:Pressure; D013016:Sound; D013997:Time Factors