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Sparse stimuli for cochlear implants
Full text linkPublication in the conference proceedings of EUSIPCO, Lausanne, Switzerland, 200
Techniques for neonatal hearing screening
No full textThe aim of screening of hearing in neonates is to concentrate cases with material disorder into a manageable group that may be referred for more definitive diagnostic testing. Material disorder is defined as a permanent bilateral hearing impairment of at least 40 dB averaged over the frequencies 0.5, 1, 2, and 4 kHz. The two most common approaches involve automated auditory brain stem response (AABR) and transiently evoked to acoustic emission (TEOAE) techniques. Both techniques can achieve adequate
specificity in excess of 95%. Provisional estimates of sensitivity suggest that 80 to 90% of cases will be correctly classified, which, although not ideal, is adequate for the purpose. Conventional AABR and TEOAE techniques do not provide frequency-specific threshold estimates. Implementation and validation of steady-state evoked potential (SSEP) and distortion product otoacoustic emission (DPOAE) techniques may add this information. It is concluded that current techniques are fit for the purpose of effective neonatal hearing screening programs
Development of a quality of life measure for adult patients with sequential bilateral cochlear implants
No full textIndependent component analysis, a new framework for speech processing of cochlear implant?
No full textTransient evoked otoacoustic emission input-output function variation in a large sample of neonates and implications for screening. (In special issue: Focus Issue: Neonatal Health Screening)
No full textWe performed a retrospective analysis of TEOAEs from 1415 neonatal ears to investigate whether the application of linear averaging techniques may provide greater screening specificity than conventional nonlinear averaging techniques. Pass criteria were based on correlations between replicate averages, and pass rates were compared between linear and nonlinear averaging techniques. The linear averaging technique gave a higher pass rate as hypothesized, so that 35% of ears that passed using the linear method failed using the nonlinear method. In addition, lack of saturation was more evident for the short-latency components of the TEOAE. These results, from a large sample of recordings obtained under field conditions, indicate that there is potential to improve specificity of neonatal TEOAE screening using linear averaging techniques. A combination of linear and nonlinear techniques for the long and short latency components of the TEOAE, respectively, may offer further advantages
Sparseness and speech perception in noise
No full textCan we model speech recognition in noise by exploring higher order statistics of the combined signal? How will changes in these statistics affect speech perception in noise? This study addresses these questions in two experiments. One investigated the relationship between an established "glimpsing" model and the fourth order statistic, kurtosis. The glimpsing model [1] proposes that listeners can explore the local speech-to-noise ratio (SNR) in short time segments (glimpses) and focus on areas where SNR is high. Results showed that there is a very high correlation between percentages of glimpsing area and kurtosis (r = 0.99;p < 0.01), suggesting that kurtosis can serve as a simpler index for measuring glimpsing. The experiment also examined the association between kurtosis and recognition of nonsense words (vowel-consonant-vowel, VCV) in babble modulated noise, also showing very high correlation (r = 0.97;p < 0.01). Another separate study focused on the relationship of sparseness to speech recognition score for VCV words in natural babble noise made of 100 people talking simultaneously [2]. Results show that there is also high correlation between kurtosis and speech recognition score with this noise. Logistic regression analysis to obtain the kurtosis for 50% correct showed this was achieved at a kurtosis of approximately 1.
Learning to discriminate interaural time differences: an exploratory study with amplitude-modulated stimuli. Aprendiendo a discriminar diferencias inter-auriculares de tiempo: un estudio exploratorio con estímulos de amplitud modulada
No full textThe advent of bilateral cochlear implants (CIs) has increased interest in learning on binaural tasks, and studies in normal-hearing listeners provide important background information. However, few studies have considered learning with discrimination of interaural time difference (ITD). Here, learning with ITD was explored using stimuli that are more relevant to bilateral CIs than used previously. Inexperienced listeners were trained with envelope-based ITD using high-frequency amplitude-modulated tones with or without an interaural carrier frequency difference (IFD), the former to simulate asymmetrical bilateral CI insertions. All were tested with and without IFD before and after training. In most listeners, ITD thresholds improved substantially with training, not necessarily reaching asymptote after 3000 trials. In these, the magnitude and time-course of learning was larger than anticipated from a previous study with low-frequency ITD. Learning generalized across IFD and the effect of IFD on ITD thresholds at post-test was smaller than reported previously. These results have implications for studies of bilateral CIs, such as the need to provide extensive training to avoid over-estimating any apparent ‘impairment’.
El advenimiento de los implantes cocleares bilaterales (CI) ha aumentado el interés en aprender sobre tareas binauriculares, y los estudios en sujetos oyentes normales han aportado importante información pertinente. Sin embargo, pocos estudios han considerado el estudio del aprendizaje con base en la discriminación de diferencias interauriculares de tiempo (ITD). Aquí, el aprendizaje con ITD fue explorado utilizando estímulos más relevantes para los CI bilaterales que los usados previamente. Se entrenó a oyentes sin experiencia con una ITD con base en envolventes que comprendían tonos de alta frecuencia de amplitud modulada, con o sin diferencia interauricular de la frecuencia portadora (IFD), esta última para simular inserciones bilaterales asimétricas de CI. Todos fueron evaluados con y sin IFD antes y después del entrenamiento, sin alcanzar necesariamente la asíntota después de 3000 intentos. En ellos, la magnitud y el tiempo del aprendizaje fue mayor de lo anticipado en un estudio con una ITD de baja frecuencia. El aprendizaje en general en todas las IFD y el efecto de la IFD sobre los umbrales de ITD después de la prueba fue similar a los reportes previos. Estos resultados tienen implicaciones en los estudios de CI bilaterales, tales como la necesidad de proveer amplio entrenamiento para evitar la sobre-estimación de cualquier ‘impedimento’ aparente
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