Auditory processing disorder (APD) is a label that describes a variable set of symptoms that share a common feature of difficulty listening to sounds in the absence of an actual audiological deficit (Moore, 2006). Clinical assessment of APD typically involves a test battery consisting of tests designed to examine the integrity of various auditory processes of the central auditory nervous system. Individuals with APD have difficulty recognising speech when parts of the signal are missing. One category of tests used to assess the extent to which this deficit is associated with reduced performance on the task is the low-pass filtered speech test. The University of Canterbury Adaptive Speech Test-Filtered Words (UCAST-FW) is a computer-based adaptive low-pass filtered speech test developed for the assessment of auditory processing skills in adults and children. Earlier studies with the UCAST-FW (McGaffin, 2007; Sincock, 2008; Heidtke, 2010; Abu-Hijleh, 2011) have produced encouraging results. However, there appear to be a number of confounding factors. The UCAST-FW is testing New Zealand listeners using an Australian recording of American test material. The purpose of the current study was to develop a new four-alternative forced choice test to replace the Northwestern University Children’s Perception of Speech (NU-CHIPS) stimuli the UCAST-FW currently utilises. The new test consists of 98 sets of four test items, (one target item and three foil alternatives) designed to be used in a four-alternative forced choice picture-pointing procedure. Phonemic analysis of the new word list and the NU-CHIPS word lists revealed a similar distribution of phonemes for target words of both word lists. The development of the new word list is described and the clinical applicability is explored.

Bakgrund: Monaurala lågredundanta taltester används, tillsammans med andra tester i testbatterier, för att undersöka centrala auditiva funktioner. Testgrupper som ingår i monaurala lågredundanta taltester är: lågpassfiltrerade taltester, tal-i-brus tester och tidskomprimerade taltester. Syfte: Syftet var att ta reda på vilka monaurala lågredundanta taltester som finns och vilka resultat man kan få på dessa. Metod: Litteraturstudie där experimentella studier har använts. Resultat: De monaurala lågredundanta taltester som har använts i de studerade artiklarna är filtrerat tal, meningar-i-brus, ord-i-brus, taluppfattning-i-brus, tal-i-brus, SPIN, R-SPIN, SSI/MCI, SSI/ICM, SIN, tidskomprimerade ord med olika kompressionsgrader, hackat tal, The Compressed Sentence Test och SCAN-A, SCAN-C med undertesterna Auditory Figure Ground och filtrerade ord. Försökspersoner med hörselnedsättning får signifikant sämre resultat än normalhörande på många av testerna. Barn får sämre resultat på flera av testerna jämfört med vuxna. Slutsatser: Det finns många olika monaurala lågredundanta taltester. De valda artiklarna tar upp fler monaurala lågredundanta taltester än vad som nämns i använd referenslitteratur.

Graduation date: 2006 / Presented on 2005-12-02 / An empirical statistical model is developed that relates the non-tidal motion of the ocean surface currents off the Oregon coast to forecasts of the coastal winds. The empirical statistical model is then used to produce predictions of the surface currents that are evaluated for their agreement with measured currents. Measurements of the ocean surface currents were made at 6 km resolution using Long-Range CODAR SeaSonde high-frequency (HF) surface current mappers and wind forecasts were provided at 12 km resolution by the North American Mesoscale (NAM) model. First, the response of the surface currents to wind-forcing measured by five coastal National Data Buoy Center (NDBC) stations was evaluated using empirical orthogonal function (EOF) analysis. A significant correlation of approximately 0.8 was found between the majority of the variability in the seasonal anomalies of the low-pass filtered surface currents and the seasonal anomalies of the low-pass filtered wind stress measurements. The U and the V components of the measured surface currents were both shown to be forced by the zonal and meridional components of the wind-stress at the NDBC stations. Next, the NAM wind forecasts were tested for agreement with the measurements of the wind at the NDBC stations. Significant correlations of around 0.8 for meridional wind stress and 0.6 for zonal wind stress were found between the seasonal anomalies of the low-pass filtered wind stress measured by the NDBC stations and the seasonal anomalies of the low-pass filtered wind stress forecast by the NAM model. Given the amount of the variance in the winds captured by the NAM model and the response of the ocean surface currents to both components of the wind, bilinear regressions were formed relating the seasonal anomalies of the low-pass filtered NAM forecasts to the seasonal anomalies of the low-pass filtered surface currents. The regressions turned NAM wind forecasts into predictions of the seasonal anomalies of the low-pass filtered surface currents. Calculations of the seasonal cycle in the surface currents, added to these predicted seasonal anomalies, produced a non-tidal estimation of the surface currents that allowed a residual difference to be calculated from recent surface current measurements. The sum of the seasonal anomalies, the seasonal cycle, and the residual formed a prediction of the non-tidal surface currents. The average error in this prediction of the surface currents off the Oregon coast remained less than 4 cm/s out through 48 hours into the future.

Le clinicien se trouve parfois confronté à des sujets qui présentent une surdité supérieure à 90 dB HL au-delà de 1 kHz avec une audition résiduelle dans les fréquences graves. Pour réhabiliter les hautes fréquences, il existe aujourd’hui différentes technologies : amplification conventionnelle, compression fréquentielle, implant cochléaire et depuis une dizaine d’année la stimulation électro-acoustique EAS qui consiste à stimuler acoustiquement les sons graves et électriquement les sons aigus via un implant cochléaire. La première partie de cette thèse a consisté à identifier les facteurs qui influencent les capacités des patients sourds partiels à traiter l’information basse fréquence de la parole. Nous avons utilisé un test d’audiométrie vocale filtrée passe-bas. Nos résultats indiquent que les scores d’intelligibilité de la parole sont positivement corrélés avec la durée de la surdité. Ceci signifie qu’avec le temps, ces sujets malentendants apprennent à comprendre avec cette audition type filtre passe-bas, à tel point que certains ont des performances supra-normales pour l’utilisation des basses fréquences. Nos résultats montrent également une corrélation négative entre l’âge d’apparition de la surdité et les scores l’intelligibilité. Ce test pourra aider le clinicien à mieux cibler l’appareillage le plus adapté à chaque profil de patient. La seconde partie de cette thèse, consacrée à l’EAS, a consisté à évaluer par des simulations chez le normo-entendant, diverses stratégies de codage du son par l’implant EAS. Actuellement, la stratégie utilisée pour l’EAS est calquée sur celle de l’implant cochléaire et nos résultats suggèrent que cette stratégie peut être optimisée. / Clinicians may face patients who have a deafness superior to 90 dB HL above 1 kHz with good lowfrequency residual hearing. Today, several technologies are available to provide high frequencies: conventional amplification, frequency compression, cochlear implant since about 10 years Electric-Acoustic Stimulation EAS which consists in stimulating acoustically low frequencies while stimulating electrically high frequency sounds via a cochlear implant. The firt part of this dissertation consisted in identifying the factors which may influence abilities of partially deaf subjects to process low-frequency speech information. We used a low-pass filtered speech test. Our results show that speech intelligibility scores are positively correlated to the duration of deafness. This means that these hearing-impaired subjects learn to understand with this lowpass-like hearing, in such a way that some of them exhibit supranormal abilities for the processing of low-frequency sounds. Our results also show a negative correlation between the age at onset of deafness and speech intelligibility scores. This test may help the clinician to better evaluate which device would be best for every patient’s profile. The second part of this dissertation, about EAS, consisted in evaluating through simulations in normal hearing listeners, several coding strategies by the EAS implant. Now the strategy used for EAS duplicates the strategy used by cochlear implants and our results suggest that this strategy could be optimized.