Lexical Stress Identification in Cochlear Implant-Simulated Speech by Non-Native Listeners.

This study investigates whether a presumed difference in the perceptibility of cues to lexical stress in spectro-temporally degraded simulated cochlear implant (CI) speech affects how listeners weight these cues during a lexical stress identification task, specifically in their non-native language. Previous research suggests that in English, listeners predominantly rely on a reduction in vowel quality as a cue to lexical stress. In Dutch, changes in the fundamental frequency (F0) contour seem to have a greater functional weight than the vowel quality contrast. Generally, non-native listeners use the cue-weighting strategies from their native language in the non-native language. Moreover, few studies have suggested that these cues to lexical stress are differently perceptible in spectro-temporally degraded electric hearing, as CI users appear to make more effective use of changes in vowel quality than of changes in the F0 contour as cues to linguistic phenomena. In this study, native Dutch learners of English identified stressed syllables in CI-simulated and non-CI-simulated Dutch and English words that contained changes in the F0 contour and vowel quality as cues to lexical stress. The results indicate that neither the cue-weighting strategies in the native language nor in the non-native language are influenced by the perceptibility of cues in the spectro-temporally degraded speech signal. These results are in contrast to our expectations based on previous research and support the idea that cue weighting is a flexible and transferable process.

Prosodic Focus Interpretation in Spectrotemporally Degraded Speech by Non-Native Listeners.

PURPOSE: This study assesses how spectrotemporal degradations that can occur in the sound transmission of a cochlear implant (CI) may influence the ability of non-native listeners to recognize the intended meaning of utterances based on the position of the prosodically focused word. Previous research suggests that perceptual accuracy and listening effort are negatively affected by CI processing (or CI simulations) or when the speech is presented in a non-native language, in a number of tasks and circumstances. How these two factors interact to affect prosodic focus interpretation, however, remains unclear. METHOD: In an online experiment, normal-hearing (NH) adolescent and adult native Dutch learners of English and a small control group of NH native English adolescents listened to CI-simulated (eight-channel noise-band vocoded) and non-CI-simulated English sentences differing in prosodically marked focus. For assessing perceptual accuracy, listeners had to indicate which of four possible context questions the speaker answered. For assessing listening effort, a dual-task paradigm was used with a secondary free recall task. RESULTS: The results indicated that prosodic focus interpretation was significantly less accurate in the CI-simulated condition compared with the non-CI-simulated condition but that listening effort was not increased. Moreover, there was no interaction between the influence of the degraded CI-simulated speech signal and listening groups in either their perceptual accuracy or listening effort. CONCLUSION: Non-native listeners are not more strongly affected by spectrotemporal degradations than native listeners, and less proficient non-native listeners are not more strongly affected by these degradations than more proficient non-native listeners.

Evolving Plasticity for Autonomous Learning under Changing Environmental Conditions.

A fundamental aspect of learning in biological neural networks is the plasticity property which allows them to modify their configurations during their lifetime. Hebbian learning is a biologically plausible mechanism for modeling the plasticity property in artificial neural networks (ANNs), based on the local interactions of neurons. However, the emergence of a coherent global learning behavior from local Hebbian plasticity rules is not very well understood. The goal of this work is to discover interpretable local Hebbian learning rules that can provide autonomous global learning. To achieve this, we use a discrete representation to encode the learning rules in a finite search space. These rules are then used to perform synaptic changes, based on the local interactions of the neurons. We employ genetic algorithms to optimize these rules to allow learning on two separate tasks (a foraging and a prey-predator scenario) in online lifetime learning settings. The resulting evolved rules converged into a set of well-defined interpretable types, that are thoroughly discussed. Notably, the performance of these rules, while adapting the ANNs during the learning tasks, is comparable to that of offline learning methods such as hill climbing.

Meta-Analysis on the Identification of Linguistic and Emotional Prosody in Cochlear Implant Users and Vocoder Simulations.

OBJECTIVES: This study quantitatively assesses how cochlear implants (CIs) and vocoder simulations of CIs influence the identification of linguistic and emotional prosody in nontonal languages. By means of meta-analysis, it was explored how accurately CI users and normal-hearing (NH) listeners of vocoder simulations (henceforth: simulation listeners) identify prosody compared with NH listeners of unprocessed speech (henceforth: NH listeners), whether this effect of electric hearing differs between CI users and simulation listeners, and whether the effect of electric hearing is influenced by the type of prosody that listeners identify or by the availability of specific cues in the speech signal. DESIGN: Records were found by searching the PubMed Central, Web of Science, Scopus, Science Direct, and PsycINFO databases (January 2018) using the search terms "cochlear implant prosody" and "vocoder prosody." Records (published in English) were included that reported results of experimental studies comparing CI users' and/or simulation listeners' identification of linguistic and/or emotional prosody in nontonal languages to that of NH listeners (all ages included). Studies that met the inclusion criteria were subjected to a multilevel random-effects meta-analysis. RESULTS: Sixty-four studies reported in 28 records were included in the meta-analysis. The analysis indicated that CI users and simulation listeners were less accurate in correctly identifying linguistic and emotional prosody compared with NH listeners, that the identification of emotional prosody was more strongly compromised by the electric hearing speech signal than linguistic prosody was, and that the low quality of transmission of fundamental frequency (f0) through the electric hearing speech signal was the main cause of compromised prosody identification in CI users and simulation listeners. Moreover, results indicated that the accuracy with which CI users and simulation listeners identified linguistic and emotional prosody was comparable, suggesting that vocoder simulations with carefully selected parameters can provide a good estimate of how prosody may be identified by CI users. CONCLUSIONS: The meta-analysis revealed a robust negative effect of electric hearing, where CIs and vocoder simulations had a similar negative influence on the identification of linguistic and emotional prosody, which seemed mainly due to inadequate transmission of f0 cues through the degraded electric hearing speech signal of CIs and vocoder simulations.

Public Space Users' Soundscape Evaluations in Relation to Their Activities. An Amsterdam-Based Study.

Understanding the relationship between people and their soundscapes in an urban context of innumerable and diverse sensory stimulations is a difficult endeavor. What public space users hear and how they evaluate it in relation to their performed or intended activities can influence users' engagement with their spaces as well as their assessment of suitability of public space for their needs or expectations. While the interaction between the auditory experience and activity is a topic gaining momentum in soundscape research, capturing the complexity of this relationship in context remains a multifaceted challenge. In this paper, we address this challenge by researching the user-soundscape relationships in relation to users' activities. Building on previous soundscape studies, we explore the role and interaction of three potentially influencing factors in users' soundscape evaluations: level of social interaction of users' activities, familiarity and expectations, and we employ affordance theory to research the ways in which users bring their soundscapes into use. To this end, we employ a mixed methods design, combining quantitative, qualitative and spatial analyses to analyze how users of three public spaces in Amsterdam evaluate their soundscapes in relation to their activities. We documented the use of an urban park in Amsterdam through non-intrusive behavioral mapping to collect spatial data on observable categories of activities, and integrated our observations with on site questionnaires on ranked soundscape evaluations and free responses detailing users' evaluations, collected at the same time from park users. One of our key findings is that solitary and socially interactive respondents evaluate their soundscapes differently in relation to their activities, with the latter offering higher suitability and lower disruption ratings than the former; this points to qualitatively different auditory experiences, analyzed further based on users' open-ended justifications for their evaluations. We provide a methodological contribution (adding to existing soundscape evaluation methodologies), an empirical contribution (providing insight on how users explain their soundscape evaluations in relation to their activities) and a policy and design-related contribution, offering additional insight on a transferable methodology and process that practitioners can employ in their work on the built environment to address the multisensory experience of public spaces.