RESUMEN
OBJECTIVE: To introduce the urban outdoor version of the Situated Phoneme (SiP) test and investigate its test-retest reliability. DESIGN: Phonemic discrimination scores in matched-spectrum real-world (MSRW) maskers from an urban outdoor environment were measured using a three-alternative forced choice test paradigm at different phoneme-to-noise ratios (PNR). Each measurement was repeated twice. Test-retest scores for the full 84-trial SiP-test, as well as for four types of contrasting phonemes, were analysed and compared to critical difference scores based on binomial confidence intervals. STUDY SAMPLE: Seventy-two adult native speakers of Swedish (26-83 years) with symmetric hearing threshold levels ranging from normal hearing to severe sensorineural hearing loss. RESULTS: Test-retest scores did not differ significantly for the whole test, or for the subtests analysed. A lower amount of test-retest score difference than expected exceeded the bounds of the corresponding critical difference intervals. CONCLUSIONS: The urban outdoor SiP-test has high test-retest reliability. This information can help audiologists to interpret test scores attained with the urban outdoor SiP-test.
RESUMEN
The human cochlea transforms sound waves into electrical signals in the acoustic nerve fibers with high acuity. This transformation occurs via vibrating anisotropic membranes (basilar and tectorial membranes) and frequency-specific hair cell receptors. Frequency-positions can be mapped within the cochlea to create a tonotopic chart which fits an almost-exponential function with lowest frequencies positioned apically and highest frequencies positioned at the cochlear base (Bekesy 1960, Greenwood 1961). To date, models of frequency positions have been based on a two-dimensional analysis with inaccurate representations of the cochlear hook region. In the present study, the first three-dimensional frequency analysis of the cochlea using dendritic mapping to obtain accurate tonotopic maps of the human basilar membrane/organ of Corti and the spiral ganglion was performed. A novel imaging technique, synchrotron radiation phase-contrast imaging, was used and a spiral ganglion frequency function was estimated by nonlinear least squares fitting a Greenwood-like function (F = A (10ax - K)) to the data. The three-dimensional tonotopic data presented herein has large implications for validating electrode position and creating customized frequency maps for cochlear implant recipients.
