Effects of training on intelligbility and integration of sine-wave speech

Although the auditory signal usually provides sufficient information for speech perception, visual cues become important when the auditory signal is compromised, as in the case of a hearing loss. However, research has shown that visual cues are used even when the auditory signal is completely intelligible (McGurk & MacDonald, 1976). Subsequent studies have investigated the impact of reducing the quality of auditory information on the integration process. Grant and Seitz (1998) studied audiovisual integration by hearing-impaired subjects, and reported that even when the auditory input is poor, speech perception can improve with the aid of visual cues. Integration for artificially reduced auditory inputs has also been investigated. One form of reduction was that used by Remez et al. (1981), who reduced speech signals to three time-varying sinusoids following the formants of the speech (“sine-wave speech”). Remez et al. showed that sine-wave speech can be highly intelligible in sentences, but in studies of audio-visual perception of individual syllables, sine-wave reductions have yielded poor performance (e.g., Anderson, 2007). It is possible that the relative unfamiliarity of this form of speech led to the poor results in integration studies. This question was addressed by Exner (2008), who evaluated the effects of increased exposure to sine-wave syllables on auditory only and audio-visual perception. She found that even two hours of training produced significant improvement in performance. However, it was not clear in her study was whether performance had reached asymptotic levels. The present study investigated the effects of longer training periods to determine if further improvements to sine-wave performance can be achieved. Five listeners received ten hours of auditory only training with eight syllables spoken by three talkers. Results showed significant improvement across training sessions, but the amount of audio-visual integration did not change. This supports the argument of Grant & Seitz (1998) that integration is a process independent of auditory or visual processing.ASC Undergraduate ScholarshipSBS Undergraduate Research Scholarship.No embarg

A critical analysis of three near-infrared photometric methods of estimating distances to cataclysmic variables

A critical analysis of three methods of estimating distances to cataclysmic variables (CVs) is performed. These methods, by Ak et al., Beuermann, and Knigge, all use near-infrared (JHK or Ks) magnitudes and the Barnes-Evans relation. We compare all three methods to distances measured by trigonometric parallax by Thorstensen, with Hubble Space Telescope, and with the HIPPARCOS spacecraft. We find that the method of Ak et al. works best overall for all CVs, predicting distances on the average 4% less than those measured by trigonometric parallaxes. The method of Beuermann overestimates distances by 52%. The method of Knigge underestimates distances by 26%, although this was only ever meant as a lower limit, since it assumes all light comes from the secondary star.Comment: 17 pages, 7 figures, 2 tables; accepted for publication in New Astronom

Quasi-periodic oscillations in accreting magnetic white dwarfs II. The asset of numerical modelling for interpreting observations

Magnetic cataclysmic variables are close binary systems containing a strongly magnetized white dwarf that accretes matter coming from an M-dwarf companion. High-energy radiation coming from those objects is emitted from the accretion column close to the white dwarf photosphere at the impact region. Its properties depend on the characteristics of the white dwarf and an accurate accretion column model allows the properties of the binary system to be inferred, such as the white dwarf mass, its magnetic field, and the accretion rate. We study the temporal and spectral behaviour of the accretion region and use the tools we developed to accurately connect the simulation results to the X-ray and optical astronomical observations. The radiation hydrodynamics code Hades was adapted to simulate this specific accretion phenomena. Classical approaches were used to model the radiative losses of the two main radiative processes: bremsstrahlung and cyclotron. The oscillation frequencies and amplitudes in the X-ray and optical domains are studied to compare those numerical results to observational ones. Different dimensional formulae were developed to complete the numerical evaluations. The complete characterization of the emitting region is described for the two main radiative regimes: when only the bremsstrahlung losses and when both cyclotron and bremsstrahlung losses are considered. The effect of the non-linear cooling in- stability regime on the accretion column behaviour is analysed. Variation in luminosity on short timescales (~ 1 s quasi-periodic oscillations) is an expected consequence of this specific dynamic. The importance of secondary shock instability on the quasi-periodic oscillation phenomenon is discussed. The stabilization effect of the cyclotron process is confirmed by our numerical simulations, as well as the power distribution in the various modes of oscillation.Comment: 13 pages, 13 figures, 2 tables. Accepted for publication in A&

Sacrificing their Careers for their Families? An Analysis of the Family Pay Penalty in Europe

This paper examines the extent of and the mechanisms behind the penalty to motherhood in six European countries. Each country provides different levels of support for maternal employment allowing us to determine institutional effects on labour market outcome. While mothers tend to earn less than non-mothers, the penalty to motherhood is considerably lower in countries with policy support for working mothers. The paper establishes the United Kingdom and West Germany to have the least policy support for working mothers as well as the largest penalties to motherhood