Contrast preservation and constraints on individual phonetic variation

Ferdinand de Saussure, one of the founders of modern Linguistics, described language as a system where everything holds together. Regarding the sounds of language, this has led to the current view that the phonology of a language consists of a complex system of relations between contrastive phonemes. In this dissertation, I test whether there are constraints on individual phonetic variation from a multivariate perspective due to this system of relations, and how these constraints interact with contrast preservation. Two main views of contrast preservation are considered. The first view is that contrast preservation is merely an outcome of other regular phonetic processes that affect multiple consonants simultaneously. The second view is that contrast preservation acts as a constraint on the phonetic realization of phonemes. To this end, two phonetic experiments are performed. In both experiments, multiple acoustic measures of intervocalic consonant strength are taken, and PCA is used for dimensionality reduction, resulting in measures of overall consonant strength. These measures are then analyzed with Bayesian linear mixed effects regression (using weakly informative priors and maximal random effects structures) in order to obtain distributional information about both populations and individual speakers. In the first experiment, word-medial intervocalic /s/ and /f/ are compared for Valladolid Spanish and Barcelona Catalan. Both Catalan and Spanish have the fricatives /s/ and /f/, neither has /v/ contrasting with /f/, and only Catalan has /z/ contrasting with /s/. The results show that Catalan /s/ is stronger than Spanish /s/, but there is no evidence for a difference between the two language’s /f/ strengths, with strong evidence that the magnitude of the difference between Catalan and Spanish /s/ is larger than the magnitude of the difference between Catalan and Spanish /f/. I argue that these results are consistent with a role for contrast preservation as a constraint, with Catalan having stronger /s/ than Spanish because lenition of Catalan /s/ causes phonetic overlap with a contrasting phoneme, while lenition of Spanish /s/ does not. In the second experiment, the simultaneous lenition of Spanish intervocalic /ptk/ and /bdg/ in three dialects (Cuzco, Peru; Lima, Peru; and Valladolid, Spain) is examined. Cuzco is found to have the strongest productions for both /ptk/ and /bdg/, Lima the weakest for both, and Valladolid in between for both. That is, the same hierarchy of strength applies in both cases, though the evidence for the difference between Valladolid and Lima /ptk/ is considerably weaker than the evidence for the other differences. I argue that the results are consistent with constraints on multivariate variation at the dialectal level, but that further research is required to see how constraints at the individual level relate to population differences. Examining individual variation in both experiments, I find that the degree to which an individual speaker lenites /f/ is correlated with the degree to which they lenite /s/, and that the degree to which they lenite /ptk/ is correlated with both the degree to which they lenite /bdg/ and the degree to which they lenite /sf/. These correlations represent a significant constraint on individual phonetic variation from a multivariate perspective. While a connection between individuals’ /ptk/ and /bdg/ lenitions can be explained by both the constraint and outcome views of contrast preservation, the correlation between /sf/ and /ptk/ and the correlation between /s/ and /f/ lend support to the outcome view, and Catalan having stronger /s/ than Spanish but not stronger /f/ lends support to the constraint view. I argue for a framework in which acoustic lenition in a variety of intervocalic consonants may share a common articulatory source of lenition, giving rise to constraints on individual phonetic variation that may lead to contrast preservation as an outcome, but where there may additionally be a role for contrast preservation as a constraint. I conclude by discussing the importance of further acoustic studies that use the methodologies employed here, and studies that explore the articulatory and perceptual implications of the results. In the first experiment, word-medial intervocalic /s/ and /f/ are compared for Valladolid Spanish and Barcelona Catalan. Both Catalan and Spanish have the fricatives /s/ and /f/, neither has /v/ contrasting with /f/, and only Catalan has /z/ contrasting with /s/. The results show that Catalan /s/ is stronger than Spanish /s/, but there is no evidence for a difference between the two language’s /f/ strengths, with strong evidence that the magnitude of the difference between Catalan and Spanish /s/ is larger than the magnitude of the difference between Catalan and Spanish /f/. I argue that these results are consistent with a role for contrast preservation as a constraint, with Catalan having stronger /s/ than Spanish because lenition of Catalan /s/ causes phonetic overlap with a contrasting phoneme, while lenition of Spanish /s/ does not. In the second experiment, the simultaneous lenition of Spanish intervocalic /ptk/ and /bdg/ in three dialects (Cuzco, Peru; Lima, Peru; and Valladolid, Spain) is examined. Cuzco is found to have the strongest productions for both /ptk/ and /bdg/, Lima the weakest for both, and Valladolid in between for both. That is, the same hierarchy of strength applies in both cases, though the evidence for the difference between Valladolid and Lima /ptk/ is considerably weaker than the evidence for the other differences. I argue that the results are consistent with constraints on multivariate variation at the dialectal level, but that further research is required to see how constraints at the individual level relate to population differences. Examining individual variation in both experiments, I find that the degree to which an individual speaker lenites /f/ is correlated with the degree to which they lenite /s/, and that the degree to which they lenite /ptk/ is correlated with both the degree to which they lenite /bdg/ and the degree to which they lenite /sf/. These correlations represent a significant constraint on individual phonetic variation from a multivariate perspective. While a connection between individuals’ /ptk/ and /bdg/ lenitions can be explained by both the constraint and outcome views of contrast preservation, the correlation between /sf/ and /ptk/ and the correlation between /s/ and /f/ lend support to the outcome view, and Catalan having stronger /s/ than Spanish but not stronger /f/ lends support to the constraint view. I argue for a framework in which acoustic lenition in a variety of intervocalic consonants may share a common articulatory source of lenition, giving rise to constraints on individual phonetic variation which may lead to contrast preservation as an outcome, but where there may additionally be a role for contrast preservation as a constraint. I conclude by discussing the importance of further acoustic studies which use the methodologies employed here, and studies which explore the articulatory and perceptual implications of the results

Biogeochemical Characterisation of an Alum Dosed Stream: Implications for Phosphate Cycling in Lake Rotoehu

Lakes are highly valued freshwater ecosystems which provide many goods and services upon which humans are reliant. Eutrophication of waterways, driven by the over-enrichment of nutrients such as phosphorus and nitrogen, is a threat to the future quality of water resources globally. Lake restoration methods are increasingly being employed to improve eutrophic waterways, via numerous catchment derived and in-lake approaches. However, spatio-temporal heterogeneity in physicochemical and biogeochemical conditions within lakes may restrict the efficacy of restoration methods. This thesis explores in-stream alum dosing as a lake remediation strategy for the purpose of dissolved phosphorus inactivation, and its physicochemical and biogeochemical interaction and fate within Lake Rotoehu, New Zealand. Laboratory and field measurements were undertaken at Lake Rotoehu, on New Zealand’s North Island. The shallow, polymictic lake resides in an active volcanic area with geothermal inputs, and is subject to several management issues including elevated nutrient concentrations, invasive macrophytes, and frequent cyanobacteria blooms. The geothermal Waitangi Springs, which discharge into Lake Rotoehu, contribute ~69 % of the lake’s total ionic content, and are responsible for enhanced concentrations of biologically limiting nutrients including phosphorus, silicon, nitrate, ammonium, and iron. In an effort to curb in-lake phosphorus levels, in-stream alum-dosing has been employed in order to floc out dissolved reactive phosphorus (DRP), through chemical adsorption and sedimentation. The results presented here, culminate from an investigation of the physicochemical and geochemical dynamics across the mixing zone from the Waitangi Springs geothermal stream outlet across Te Wairoa Bay to the main lake body. A combination of approaches was used: two field experiments with fixed location and transect measurements, laboratory analysis and geochemical speciation modelling with PHREEQC. Results show sharp changes in physicochemical water properties across the mixing zone within the bay: pH, O2 and dissolved reactive phosphorus values increased with distance from the stream outlet, whereas major ion concentrations, temperature and conductivity values decreased. Initial in-stream phosphorus stripping through alum dosing is effective in reducing the DRP load by ~50 % of background concentration. As alum is introduced to the stream water (~pH 6) it precipitates to form amorphous aluminium hydroxide (Al(OH)3(am)) and adsorbs phosphorus via hydroxyl ligand exchange. However, elevated levels of iron in amorphous hydrous ferric hydroxides Fe(OH)3(am) are also likely to be contributing to natural phosphorus binding capacity. Sediment core data also indicated that settled Al(OH)3(am) floc and Fe(OH)3(am) particulates were primarily concentrated within the inner portion of Te Wairoa Bay near the Waitangi Springs outlet. Surface water physicochemical and geochemical concentrations were spatially resolved and indicated distinct mixing boundaries (pH, DO, temp) and patchiness (Al, Fe, DRP) within Te Wairoa Bay associated with the locations and configuration of dense submerged macrophytes (Ceratophyllum demersum). Geochemical speciation modelling also indicated that the primary dissolved Al species was Al(OH)4- under the observed daytime conditions, and that Fe was primarily in colloidal form Fe(OH)3(am), which was confirmed through diffusive gradients in thin films (DGT) measurements. A diel sampling experiment also confirmed that as alum-dosed water enters the lake, daytime biogeochemical conditions driven by C. demersum alter physicochemical water properties from ~pH 6 to ~pH 9, and DO (supersaturation) via increased photosynthesis. Diel-fluxes in geochemical solubility (Al, Fe, and DRP) responded to physicochemical shifts (pH, O2,) and demonstrate that C. demersum have the capacity to influence Al solubility and DRP availability within Te Wairoa Bay. This work highlights the complexity of biogeochemical processes within aquatic freshwater ecosystems. Moreover, the results emphasise the need to account for the significant spatial and temporal heterogeneity of physicochemical parameters in the development of effective lake remediation strategies

Sound, structure and meaning : The bases of prominence ratings in English, French and Spanish

This study tests the influence of acoustic cues and non-acoustic contextual factors on listeners’ perception of prominence in three languages whose prominence systems differ in the phonological patterning of prominence and in the association of prominence with information structure—English, French and Spanish. Native speakers of each language performed an auditory rating task to mark prominent words in samples of conversational speech under two instructions: with prominence defined in terms of acoustic or meaning-related criteria. Logistic regression models tested the role of task instruction, acoustic cues and non-acoustic contextual factors in predicting binary prominence ratings of individual listeners. In all three languages we find similar effects of prosodic phrase structure and acoustic cues (F0, intensity, phone-rate) on prominence ratings, and differences in the effect of word frequency and instruction. In English, where phrasal prominence is used to convey meaning related to information structure, acoustic and meaning criteria converge on very similar prominence ratings. In French and Spanish, where prominence plays a lesser role in signaling information structure, phrasal prominence is perceived more narrowly on structural and acoustic grounds. Prominence ratings from untrained listeners correspond with ToBI pitch accent labels for each language. Distinctions in ToBI pitch accent status (nuclear, prenuclear, unaccented) are reflected in empirical and model-predicted prominence ratings. In addition, words with a ToBI pitch accent type that is typically associated with contrastive focus are more likely to be rated as prominent in Spanish and English, but no such effect is found for French. These findings are discussed in relation to probabilistic models of prominence production and perception.Peer reviewe

Are flow-vegetation interactions well represented by mimics? A case study of mangrove pneumatophores

Arrays of real mangrove pneumatophores (i.e. aboveground pencil roots) and artificial dowel mimics were constructed in a laboratory flume to examine differences in canopy flow dynamics. Compared to the uniform-height dowel canopy, the non-uniform height of the pneumatophores significantly reduced the intensity of the canopy shear, and shifted the turbulence maxima observed directly above the dowels upwards by approximately the standard deviation of the pneumatophore heights. Consequently, bed shear stresses were up to two times greater in the uniform-height dowel canopy than in a pneumatophore canopy of similar density. At the same time, ratios of the within-canopy velocity to the free-stream velocity above the canopies were not significantly altered by the heterogeneous height, shape and spatial distribution of the pneumatophores. Our results emphasize that uniform dowels are poor proxies of real pneumatophore canopies and may lead to underestimations of sediment-trapping efficiency

Perception of acoustic, informational and structural prominence in English, French, and Spanish.

International audienceNuclear prominence is assigned to a word based on information status in some languages, while its location is fixed at the end of a phrase in others. We test how this difference affects prominence perception, comparing English, Spanish and French, languages that differ in the strength of the link between informational, positional and acoustic prominence. Using the method of Rapid Prosody Transcription, we compare prominence perception in English Spanish and French in relation to phrasal position and word frequency (a correlate of information status), and by directing listeners’ attention to acoustic criteria or to informational (“meaning-based” criteria). Prominence annotations were collected for spontaneous speech excerpts from 30 listeners of each language. Statistical results of mixed-effect regression show that word frequency as an informational factor most strongly influences prominence ratings for English, where prominence is the primary expression of information status. But despite differences in the phrasal location of nuclear prominence among these languages, the structural factor of adjacency to a prosodic boundary uniformly influences prominence perception based on acoustic criteria in all languages. Listeners in all three languages tend to perceive an acoustically-cued structural prominence on the phrase-final word, suggesting the primacy of a structural nuclear prominence in prosodic theory

The perception of phrasal prominence in English, Spanish and French conversational speech

International audienceSince Bolinger's [1] discovery that pitch cues accentual prominence in English, a tension has arisen between two strategies: equating accent with pitch excursions and relying on perception for identifying accented words. This paper investigates the relation between prominence judgments from untrained listeners and accentual labels produced by trained transcribers. Naïve speakers of English, Spanish and French (30 per language) were asked to mark prominent words in excerpts of conversational speech from their native language (between 900-1100 words in each sample). Aggregated prominence scores (P-scores) were compared with experts' ToBI labels for each language. For all three languages, words ToBI-labelled as accented had substantially higher P-scores than unaccented words, and nuclear accents had higher P-scores than prenuclear ones. P-scores also discriminated among several accent types. Predictions from prior research on the relative prominence of accent labels were tested, and findings confirm that English L+H* accents are more likely to be judged as prominent than H* accents, and Spanish L+H* is more likely judged as prominent than L+>H*. However, for French, our prediction that Accentual Phrase-initial Hi is prominence-lending was not confirmed. The results establish the link between tonal accents and perceived prominence in three languages that differ in their use of contrastive prominence at the lexical and phrasal levels