Investigating supra-intelligibility aspects of speech

158 p.Synthetic and recorded speech form a great part of oureveryday listening experience, and much of our exposure tothese forms of speech occurs in potentially noisy settings such as on public transport, in the classroom or workplace, while driving, and in our homes. Optimising speech output to ensure that salient information is both correctly and effortlessly received is a main concern for the designers of applications that make use of the speech modality. Most of the focus in adapting speech output to challenging listening conditions has been on intelligibility, and specifically on enhancing intelligibility by modifying speech prior to presentation. However, the quality of the generated speech is not always satisfying for the recipient, which might lead to fatigue, or reluctance in using this communication modality. Consequently, a sole focus on intelligibility enhancement provides an incomplete picture of a listener¿s experience since the effect of modified or synthetic speech on other characteristics risks being ignored. These concerns motivate the study of 'supra-intelligibility' factors such as the additional cognitive demand that modified speech may well impose upon listeners, as well as quality, naturalness, distortion and pleasantness. This thesis reports on an investigation into two supra-intelligibility factors: listening effort and listener preferences. Differences in listening effort across four speech types (plain natural, Lombard, algorithmically-enhanced, and synthetic speech) were measured using existing methods, including pupillometry, subjective judgements, and intelligibility scores. To explore the effects of speech features on listener preferences, a new tool, SpeechAdjuster, was developed. SpeechAdjuster allows the manipulation of virtually any aspect of speech and supports the joint elicitation of listener preferences and intelligibility measures. The tool reverses the roles of listener and experimenter by allowing listeners direct control of speech characteristics in real-time. Several experiments to explore the effects of speech properties on listening preferences and intelligibility using SpeechAdjuster were conducted. Participants were permitted to change a speech feature during an open-ended adjustment phase, followed by a test phase in which they identified speech presented with the feature value selected at the end of the adjustment phase. Experiments with native normal-hearing listeners measured the consequences of allowing listeners to change speech rate, fundamental frequency, and other features which led to spectral energy redistribution. Speech stimuli were presented in both quiet and masked conditions. Results revealed that listeners prefer feature modifications similar to those observed in naturally modified speech in noise (Lombard speech). Further, Lombard speech required the least listening effort compared to either plain natural, algorithmically-enhanced, or synthetic speech. For stationary noise, as noise level increased listeners chose slower speech rates and flatter tilts compared to the original speech. Only the choice of fundamental frequency was not consistent with that observed in Lombard speech. It is possible that features such as fundamental frequency that talkers naturally modify are by-products of the speech type (e.g. hyperarticulated speech) and might not be advantageous for the listener.Findings suggest that listener preferences provide information about the processing of speech over and above that measured by intelligibility. One of the listeners¿ concerns was to maximise intelligibility. In noise, listeners preferred the feature values for which more information survived masking, choosing speech rates that led to a contrast with the modulation rate of the masker, or modifications that led to a shift of spectral energy concentration to higher frequencies compared to those of the masker. For all features being modified by listeners, preferences were evident even when intelligibility was at or close to ceiling levels. Such preferences might result from a desire to reduce the cognitive effort of understanding speech, or from a desire to reproduce the sound of typical speech features experienced in real-world noisy conditions, or to optimise the quality of the modified signal. Investigation of supra-intelligibility aspects of speech promises to improve the quality of speech enhancement algorithms, bringing with it the potential of reducing the effort of understanding artificially-modified or generated forms of speech

Listeners’ Spectral Reallocation Preferences for Speech in Noise

Modifying the spectrum of recorded or synthetic speech is an effective strategy for boosting intelligibility in noise without increasing the speech level. However, the wider impact of changes to the spectral energy distribution of speech is poorly understood. The present study explored the influence of spectral modifications using an experimental paradigm in which listeners were able to adjust speech parameters directly with real-time audio feedback, allowing the joint elicitation of preferences and word recognition scores. In two experiments involving full-bandwidth and bandwidth-limited speech, respectively, listeners adjusted one of eight features that altered the speech spectrum, and then immediately carried out a sentence-in-noise recognition task at the chosen setting. Listeners’ preferred adjustments in most conditions involved the transfer of speech energy from the sub-1 kHz region to the 1–4 kHz range. Preferences were not random, even when intelligibility was at the ceiling or constant across a range of adjustment values, suggesting that listener choices encompass more than a desire to maintain comprehensibility.Olympia Simantiraki was funded by the European Commission under the Marie Curie European Training Network ENRICH (675324)

The impact of speech type on listening effort and intelligibility for native and non-native listeners

Listeners are routinely exposed to many different types of speech, including artificially-enhanced and synthetic speech, styles which deviate to a greater or lesser extent from naturally-spoken exemplars. While the impact of differing speech types on intelligibility is well-studied, it is less clear how such types affect cognitive processing demands, and in particular whether those speech forms with the greatest intelligibility in noise have a commensurately lower listening effort. The current study measured intelligibility, self-reported listening effort, and a pupillometry-based measure of cognitive load for four distinct types of speech: (i) plain i.e. natural unmodified speech; (ii) Lombard speech, a naturally-enhanced form which occurs when speaking in the presence of noise; (iii) artificially-enhanced speech which involves spectral shaping and dynamic range compression; and (iv) speech synthesized from text. In the first experiment a cohort of 26 native listeners responded to the four speech types in three levels of speech-shaped noise. In a second experiment, 31 non-native listeners underwent the same procedure at more favorable signal-to-noise ratios, chosen since second language listening in noise has a more detrimental effect on intelligibility than listening in a first language. For both native and non-native listeners, artificially-enhanced speech was the most intelligible and led to the lowest subjective effort ratings, while the reverse was true for synthetic speech. However, pupil data suggested that Lombard speech elicited the lowest processing demands overall. These outcomes indicate that the relationship between intelligibility and cognitive processing demands is not a simple inverse, but is mediated by speech type. The findings of the current study motivate the search for speech modification algorithms that are optimized for both intelligibility and listening effort.</p

The impact of speech type on listening effort and intelligibility for native and non-native listeners

Listeners are routinely exposed to many different types of speech, including artificially-enhanced and synthetic speech, styles which deviate to a greater or lesser extent from naturally-spoken exemplars. While the impact of differing speech types on intelligibility is well-studied, it is less clear how such types affect cognitive processing demands, and in particular whether those speech forms with the greatest intelligibility in noise have a commensurately lower listening effort. The current study measured intelligibility, self-reported listening effort, and a pupillometry-based measure of cognitive load for four distinct types of speech: (i) plain i.e. natural unmodified speech; (ii) Lombard speech, a naturally-enhanced form which occurs when speaking in the presence of noise; (iii) artificially-enhanced speech which involves spectral shaping and dynamic range compression; and (iv) speech synthesized from text. In the first experiment a cohort of 26 native listeners responded to the four speech types in three levels of speech-shaped noise. In a second experiment, 31 non-native listeners underwent the same procedure at more favorable signal-to-noise ratios, chosen since second language listening in noise has a more detrimental effect on intelligibility than listening in a first language. For both native and non-native listeners, artificially-enhanced speech was the most intelligible and led to the lowest subjective effort ratings, while the reverse was true for synthetic speech. However, pupil data suggested that Lombard speech elicited the lowest processing demands overall. These outcomes indicate that the relationship between intelligibility and cognitive processing demands is not a simple inverse, but is mediated by speech type. The findings of the current study motivate the search for speech modification algorithms that are optimized for both intelligibility and listening effort

Spectroscopic detection improves multi-color quantification in fluorescence tomography

Simultaneous detection of several biological processes in vivo is a common requirement in biomedical and biological applications, and in order to address this issue the use of multiple fluorophores is usually the method of choice. Existing methodologies however, do not provide quantitative feedback of multiple fluorophore concentrations in small animals in vivo when their spectra overlap, especially when imaging the whole body in 3D. Here we present an approach where a spectroscopic module has been implemented into a custom-built Fluorescence Molecular Tomography (FMT) system. In contrast with other multispectral approaches, this multimodal imaging system is capable of recording the fluorescence spectra from each illumination point during a tomographic measurement. In situ spectral information can thus be extracted and used to improve the separation of overlapping signals associated with different fluorophores. The results of this new approach tested on both in vitro and in vivo experiments are presented, proving that accurate recovery of fluorophore concentrations can be obtained from multispectral tomography data even in the presence of high autofluorescence

Unidimensional scaling: A linear programming approach minimizing absolute deviations

Unidimensional Scaling, Seriation, Linear Programming, Mixed Integer Programming,

Μέθοδοι εσωτερικού σημείου για γραμμικά και μεικτά προβλήματα συμπληρωματικότητας

An infeasible interior-point method with backtracking line search is proposed to solve the linear complementarity and the general mixed complementarity problem. The standard nonlinear complementarity problem is a special case of the latter problem. The algorithm is based on a method for the general nonlinear programming problem. For this algorithm we prove global convergence from any strictly positive staring point, under minor assumptions. Numerical results are reported which demonstrate very good computational performance on large scale linear complementarity problems as well as on a standard set of mixed complementarity problems.In the case of the general nonlinear program, the Karush-Kuhn-Tucker conditions can be stated as a mixed complementarity problem. Computational results are also reported on a large collection of nonlinear programming problems.Finally, the infinite horizon alternating move duopoly method is studied. It is shown that the necessary and sufficient conditions for a symmetric Markov perfect equilibrium of the model can be formulated as a nonlinear complementarity problem. When only necessary conditions are considered, a linear complementarity problem results. The performance of the algorithm when started from different points, is investigated on a specific example of this model. This example is known to have at least two equilibria, one is an Edgeworth cycle and the other is of the kinked demand curve type. Some sensitivity analysis of the solution around these two equilibria is provided.Προτείνεται ένας μη εφικτός αλγόριθμος εσωτερικού σημείου για την επίλυση γραμμικών και μεικτών προβλημάτων συμπληρωματικότας. Το σύνηθες μη γραμμικό πρόβλημα συμπληρωματικότητας αποτελεί ειδική περίπτωση του μεικτού προβλήματος. Ο αλγόριθμος βασίζεται σε μια μέθοδο για το γενικό πρόβλημα μη γραμμικού προγραμματισμού. Για αυτόν τον αλγόριθμο αποδεικνύουμε την καθολική σύγκλιση από οποιοδήποτε αυστηρά θετικό αρχικό σημείο, κάτω ελάσσονες προϋποθέσεις. Συμπεριλαμβάνονται αριθμητικά αποτελέσματα που καταδεικνύουν πολύ καλές υπολογιστικές επιδόσεις τους προτεινόμενου αλγορίθμου σε μεγάλης κλίμακας γραμμικά προβλήματα συμπληρωματικότητας καθώς και σε ένα τυπικό σύνολο μεικτών προβλημάτων συμπληρωματικότητας.Για την περίπτωση του γενικού μη γραμμικού προβλήματος, οι συνθήκες Karush-Kuhn-Tucker μπορούν να γραφούν σε μορφή ενός μεικτού προβλήματος συμπληρωματικότητας. Η εργασία περιλαμβάνει υπολογιστικά αποτελέσματα εφαρμογής του αλγορίθμους σε μία μεγάλη συλλογή μη γραμμικών προβλημάτων προγραμματισμού.Τέλος, μελετάται το ατέρμονο, εναλλασσόμενης κίνησης μοντέλο δυοπωλίου. Αποδεικνύεται ότι οι αναγκαίες και ικανές συνθήκες για ένα συμμετρικό Markov perfect σημείο ισορροπίας για το μοντέλο αυτό, μπορούν να διατυπωθούν ως ένα μη γραμμικό πρόβλημα συμπληρωματικότητας. Μάλιστα, όταν λαμβάνονται υπόψη μόνο οι αναγκαίες συνθήκες, τότε προκύπτει ένα γραμμικό πρόβλημα συμπληρωματικότητας.Ερευνάται, η απόδοση του αλγορίθμου, από διαφορετικά σημεία εκκίνησης, πάνω σε ένα συγκεκριμένο παράδειγμα δυοπωλίου. Αυτό το παράδειγμα είναι γνωστό ότι έχει τουλάχιστον δύο σημεία ισορροπίας, το ένα είναι ένας κύκλος Edgeworth και το άλλο είναι τύπου μη ομαλής καμπύλης ζήτησης. Τέλος, παρέχεται ανάλυση ευαισθησίας της λύσης γύρω από αυτά τα δύο σημεία ισορροπίας

Remediation of polluted underground aquifer from organic and inorganic pollutants with the application of the permeable reactive barriers technology

The scientific community focuses on finding methods for the removal of the toxic pollutants from the ground and groundwater with high performance and low cost. The reactive barriers technology is based on the application of the appropriate filters downstream to the pollution source. The filters should have low cost, high availability and high efficiency for a wide range of pollutants in order to be an optimal solution for reactive barriers.Τhe present study focuses on the removal of toxic and frequently encountered contaminants from groundwater. The pollutants’ selection was based on their frequent appearance in ground and groundwater as well as their toxicity for the environment and humans. This thesis studied two types of sludge (unaerobically digested and undigested), two types of compost (unmature and mature) and an inorganic material, Greek natural zeolite. Full characterization of these materials took place, in order to determine accurately the parameters, which have direct effects on the organic and inorganic pollutants sorption. Batch experiments under stable conditions took place in order to determine the sorption of the organic volatile hydrocarbons (Benzene, Toluene, Ethylbenzene, m-p,o Xylenes -BTEX) and the inorganic contaminants (Cd, Zn) from the five materials. The effects of the contact time and the material dose were studied for the five materials. The ideal organic material was selected both in terms of quality and suitability for ground disposal and in terms of pollutants’ binding based on these experimental results. The suitability of all the studied materials for application in the reactive barriers technology follows the order: mature compost>zeolite>unmature compost>undigested sludge>digested sludge. Mature compost and zeolite were further analyzed. The effect of the initial concentration and the pH value were also studied for both materials. In addition, the existence of competing phenomena in polluted solutions which contain both BTEX and metals, were studied. The experimental results of kinetic and isotherm experiments were applied to widely used mathematical models in order to study the possibility of their reliable use.The study was extended for zeolite and compost to column experiments. The experiments took place in cylindrical columns by applying vertical up-flow. These series of experiments offer better simulation to the real field conditions. In addition, the effect of the initial concentration, the flow rate and the material’s quantity in the column as well as the desorption capacity of both materials and the seven studied pollutants were studied. The column experimental results were applied to respective mathematical models in order to find the most reliable model.Finally, this dissertation includes experiments at a larger scale by utilizing the natural flow. In more details, the experimental setup was built to simulate the stratification that occurs in the subsurface and the reactive barriers technology. The possibility of the simultaneous removal of organic and inorganic pollutants, the effect of the initial concentration, the simultaneous use of compost and zeolite in series and the effect of the layer’s slope were examined during these experiments. The selectivity of both materials, with small differences follows the order Cd > Zn > m,p xylenes> ο-xylene > toluene>benzene. The removal efficiency of compost and zeolite was studied for real contaminated groundwater. Last, the solution flow into the tank was simulated by the Princenton Transport Code (PTC).Η επιστημονική κοινότητα αποδίδει ιδιαίτερη έμφαση στην εξεύρεση και εφαρμογή κατάλληλων μεθόδων απομάκρυνσης τοξικών ρύπων από τα υπόγεια ύδατα με υψηλή απόδοση αλλά και χαμηλό κόστος. Μια εξ αυτών είναι η χρήση των αντιδρώντων φραγμάτων. Η παρούσα διδακτορική διατριβή επικεντρώνεται στο ζήτημα της ταυτόχρονης απομάκρυνσης επίμονων, τοξικών και συχνά εμφανιζόμενων οργανικών και ανόργανων ρύπων από υπόγειους υδροφορείς με την χρήση κατάλληλων πληρωτικών υλικών. Οι ρύποι που μελετήθηκαν, επιλέχθηκαν με κριτήριο την συχνότητα εμφάνισής τους στο υπέδαφος και τα υπόγεια ύδατα αλλά και την τοξικότητα και επικινδυνότητά τους για το περιβάλλον και τον άνθρωπο. Στην παρούσα διατριβή, επιλέχθηκαν και μελετήθηκαν ως πληρωτικά υλικά δυο είδη ιλύος (αναερόβια χωνευμένη και μη χωνευμένη ιλύς), δύο είδη κόμποστ (μη ώριμο και ώριμο) και ένα ανόργανο υλικό, ο ελληνικός φυσικός ζεόλιθος. Αρχικά, πραγματοποιήθηκε πλήρης χαρακτηρισμός των συγκεκριμένων υλικών με στόχο τον ακριβή προσδιορισμό των παραμέτρων που έχουν άμεση επίδραση στον βαθμό ρόφησης οργανικών και ανόργανων ρύπων. Ακολούθησαν, πειράματα διαλείποντος έργου υπό κατάλληλες σταθερές συνθήκες και για τα πέντε υλικά. Συγκεκριμένα, μελετήθηκε η επίδραση καθοριστικών παραμέτρων (ποσότητα υλικού και χρόνος επαφής) στον βαθμό απομάκρυνσης των μετάλλων (καδμίου και ψευδαργύρου) και των πτητικών υδρογονανθράκων (βενζόλιο, τολουόλιο, αιθυλοβενζόλιο, m, p, o ξυλόλια-BTEX) από τα υδατικά διαλύματα. Με βάση τα αποτελέσματα αυτών των πειραμάτων έγινε επιλογή του καλύτερου οργανικού υλικού τόσο από άποψη ποιότητας και καταλληλότητας διάθεσης στο έδαφος όσο και από άποψη απόδοσης στην δέσμευση των ρύπων. Η σειρά καταλληλότητας των υλικών που μελετήθηκαν με σκοπό την αξιοποίησή τους σε τεχνολογίες εξυγίανσης υπογείων υδάτων είναι η εξής: ώριμο κόμποστ > ζεόλιθος > μη ώριμο κόμποστ > μη χωνευμένη ιλύς > χωνευμένη ιλύς. Το ώριμο κόμποστ και ο ζεόλιθος διερευνήθηκαν περεταίρω. Συγκεριμένα, μελετήθηκε η επίδραση της αρχικής συγκέντρωσης των ρύπων και του pH αλλά και η πιθανή ύπαρξη ανταγωνιστικών φαινομένων παρουσία μετάλλων και BTEX. Τα πειραματικά αποτελέσματα των κινητικών και ισόθερμων πειραμάτων εφαρμόστηκαν σε ευρέως χρησιμοποιούμενα μαθηματικά μοντέλα με σκοπό να διερευνηθεί η δυνατότητα αξιόπιστης χρήσης τους. Στην συνέχεια, η έρευνα επεκτάθηκε, για τον ζεόλιθο και το ώριμο κόμποστ, σε πειράματα συνεχούς ροής. Τα πειράματα έλαβαν χώρα σε κυλινδρικές στήλες κατακόρυφης ροής από κάτω προς τα πάνω. Αυτή η σειρά πειραμάτων, προσεγγίζει περισσότερο τις πραγματικά επικρατούσες συνθήκες στο υπέδαφος σε σύγκριση με τα πειράματα διαλείποντος έργου. Πιο συγκεκριμένα, έλαβε χώρα η μελέτη της επίδρασης της αρχικής συγκέντρωσης, της ταχύτητας ροής αλλά και της δυνατότητας των δύο υλικών να εκροφούν τους ρύπους που έχουν δεσμεύσει όταν εκπλυθούν με απιονισμένο νερό ή άλλο κατάλληλο μέσο εκχύλισης. Η τρίτη σειρά πειραμάτων ολοκληρώθηκε με την διερεύνηση της χρήσης μαθηματικών μοντέλων συνεχούς ροής για την προσομοίωση των πειραματικών αποτελεσμάτων και την εξεύρεση του πιο αξιόπιστου μοντέλου.Τέλος, η διατριβή περιλαμβάνει πειράματα σε επίπεδο μεγαλύτερης κλίμακας με αξιοποίηση της φυσικής ροής. Συγκεκριμένα, κατασκευάστηκε πειραματική διάταξη με διαδοχή στρωμάτων που να αντιστοιχεί σε εκείνη που συναντάται στο υπέδαφος και στην τεχνολογία των αντιδρώντων φραγμάτων. Στα πειράματα αυτά μελετήθηκε η δυνατότητα ταυτόχρονης απομάκρυνσης οργανικών και ανόργανων ρύπων, η επίδραση της αρχικής συγκέντρωσης, η ταυτόχρονη χρήση του ώριμου κόμποστ και του ζεόλιθου σε σειρά καθώς και η επίδραση της κλίσης των στρωμάτων. H σειρά προτίμησης των ρύπων και για τα δύο υλικά με μικρές αποκλίσεις μεταξύ των πειραμάτων είναι :Cd > Zn > m,p ξυλόλια> αιθυλοβενζόλιο> ο-ξυλόλιο > τολουόλιο > βενζόλιο.Η διατριβή ολοκληρώθηκε με την μελέτη απόδοσης της πιλοτικής δεξαμενής στην εξυγίανση πραγματικών δειγμάτων από υπόγεια ύδατα περιοχής διυλιστηρίου και με προσομοίωση της ροής στην δεξαμενή μέσω της χρήσης λογισμικού (Princenton Transport Code-PTC)