F1 Dimension Research Articles

English Speakers’ Perception of Non-native Vowel Contrasts in Adverse Listening Conditions: A Discrimination Study on the German Front Rounded Vowels /y/ and /ø/

Previous research has shown that it is difficult for English speakers to distinguish the front rounded vowels /y/ and /ø/ from the back rounded vowels /u/ and /o/. In this study, we examine the effect of noise on this perceptual difficulty. In an Oddity Discrimination Task, English speakers without any knowledge of German were asked to discriminate between German-sounding pseudowords varying in the vowel both in quiet and in white noise at two signal-to-noise ratios (8 and 0 dB). In test trials, vowels of the same height were contrasted with each other, whereas a contrast with /a/ served as a control trial. Results revealed that a contrast with /a/ remained stable in every listening condition for both high and mid vowels. When contrasting vowels of the same height, however, there was a perceptual shift along the F2 dimension as the noise level increased. Although the /ø/-/o/ and particularly /y/-/u/ contrasts were the most difficult in quiet, accuracy on /i/-/y/ and /e/-/ø/ trials decreased immensely when the speech signal was masked. The German control group showed the same pattern, albeit less severe than the non-native group, suggesting that even in low-level tasks with pseudowords, there is a native advantage in speech perception in noise.

A Cross-Language Comparative Study of English and German Vowel Space Area in Swiss German L1 Speakers

It is conventional to examine vowel systems by their acoustic correlates, specifically formants. In the International Phonetic Alphabet (IPA) vowel chart, vowels are placed according to their relative positions determined by the first two formant values. This two-dimensional plane makes possible the calculation of the articulatory working space of vowels. Variations in the size and shape of the vowel space exist across gender, dialects, and languages. The present study focuses on comparing the vowel space area (VSA) in English and German produced by native Swiss German speakers, attempting to shed light on whether VSAs differ significantly with different calculation methods cross-linguistically. Given the fact that absolute formant values vary tremendously across gender, Hertz values are converted to z-scores, allowing for more direct and meaningful comparisons. While vowel normalization mitigates gender-related differences within specific languages to a large extent, there remains a significant cross-linguistic gender difference. The results reveal that for 3- and 4-vowel space there is no significant effect in language but an effect is observed in gender and vowel combination on VSA, specifically in terms of individual area and overlapping ratio. This suggests that Swiss German speakers tend to utilize the same amount of vowel space in both languages, with the only difference being the expansion of English VSA in higher F2 dimension and lower F1 dimension, as observed across all calculation methods.

Modeling the neural encoding of vowel formants in the midbrain

The first (F1) and second (F2) formants of a vowel determine its identity, making it essential to understand how these formant regions are encoded in the brain. We investigated the neural encoding of vowel formants using computational model responses of the auditory nerve and midbrain to natural vowel tokens [Hillenbrand et al., JASA 97, 3099 (1995)]. The first formant peak can be difficult to identify based on model population responses. Responses in the F1 region are more affected by the surrounding harmonic structure, whereas F2 often has a more straightforward representation in the model response. This result is surprising given the sensitivity of listeners for F1 discrimination compared to F2, reflecting Vowel Dispersion Theory [Liljencrants & Lindblom, Language 48, 839 (1972)], which favors the F1 dimension over F2. While peaks are difficult to identify, complex patterns of neural discharge rates observed across low-frequency midbrain responses may work to encode F1. These results suggest revisiting assumptions of the neural representations of formants and highlight the need for a system that evaluates overall response trends to formant regions instead of searching for formant peaks. Neural models can play an important role in understanding the structure of vowel systems. [Work supported by NIDCD-R01-010813.]

Formant-harmonic interactions and vowel perception

The technique of “turning over” in singing which causes perceivable vowel quality shifts has been attributed to the crossing over of H2 over F1. The present work seeks to validate these perceptual claims. A modified AXB discrimination task was completed by 63 speakers, consisting of Klatt synthesized vowels. Versions of the vowels (/i, u, ɑ, ɔ/) varying in the F1 (+/50 Hz) dimension, the F2 (+/−100 Hz) dimension or both F1 and F2 dimensions were used as reference “A/B” tokens, while the “X” token varied along 9 semitones in an F0 continuum. F1 of the vowel aligned to H2 at step 5 of the F0 continuum. Listeners judged whether the vowel quality of token ‘X’ (F0 modified) was closer to “A” or “B” (F1/F2 modified). Results find that listeners perceive the vowel to have a lower F1 during H2-F1 crossover, but the vowel height is perceived to be lower before and after the alignment. This pattern was more robust in the vowel height than the vowel backness dimension, with similar results across vowels. These findings were confirmed with logistic regression models. We conclude that formant harmonic crossovers have psychoacoustic effects on vowel perception, holding implications in vowel modification in singing.

Acoustic influence of L1 Spanish on L2 English vowel production

The strength of influence of the L1 vowel inventory on L2 vowel acquisition is well-documented: learners who identify an L2 phoneme as belonging to an L1 category may fail to establish a distinct category for the new phoneme (Flege, 2002), while those who establish a new category for an L2 vowel may ultimately exhibit more native-like pronunciation (Bohn & Flege, 1992). In learning an L2 with many more vowel categories than the L1, as Spanish-English bilinguals must, speaker-specific category assimilation and discrimination are important contributors to the level of accentedness and intelligibility. This study examines the influence of L1 vowels on L2 production via formants and duration of stressed and unstressed L1 Spanish/L2 English vowels. Ten advanced Spanish-English bilinguals completed a shadowing task in both languages, producing five vowels from each language in various target words. Examined in the aggregate, most vowels remained spectrally distinct along both the F1 and F2 dimensions, with a few categories collapsed across one dimension or the other; unstressed vowels raised in both languages, but raised further in English than Spanish. However, interspeaker differences in the patterns of category assimilation necessitate an individual analysis, highlighting the high level of variation in acquisition across individuals.

Multiplet analysis by strong-coupling-artifact-suppression 2D J-resolved NMR spectroscopy.

Benefitting from the capability of recording scalar (J) couplings and bonding information, 2D J-resolved NMR spectroscopy constitutes an important tool for molecular structure analysis and mixture component identification. Unfortunately, conventional 2D J-resolved experiments generally encounter challenges of insufficient spectral resolution and strong coupling artifacts. In this study, a general NMR approach is exploited to record absorption-mode artifact-free 2D J-resolved spectra. This proposal adopts the advanced triple-spin-echo pure shift yielded by chirp excitation element to eliminate J coupling splittings and preserve chemical shifts along the F2 dimension, and it additionally utilizes the echo-train J acquisition to reveal the multiplet structure along the F1 dimension in accelerated experimental acquisition. Thus, it permits one to extract multiplet structure information from crowded spectral regions in one-shot experiments, with considerable resolution advantage resulting from completely decoupling F2 dimension and absorption-mode presentation, thus facilitating analysis on complex samples. More importantly, this method grants the superior performance on suppressing strong coupling artifacts, which have been affirmed by experiments on a series of chemical samples. As a consequence, this proposed method serves as a useful tool for J coupling measurements and multiplet structure analyses on complex samples that contain crowded NMR resonances and strong coupling spin systems, and it may exhibit broad application potentials in fields of physics, chemistry, and medical science, among others.

Acoustic characteristics and placement within vowel space of full schwa in the world’s languages: A survey

Data from about one hundred languages reveal that, in spite of resulting typically from articulatory reduction of peripheral vowels in unstressed position, full schwa may also occur in stressed position in stress languages and in unreduced syllables in languages lacking stress. Formant frequency data reveal that this vowel is mid central, though somewhat shifted to the mid back unrounded area (particularly if long and placed in open syllables and at the edges of words), and exhibits a higher or lower realization depending on the number of mid vowels in the vowel system. In spite of occurring in stressed position, full schwa resembles unstressed schwa in being very short, highly variable and possibly low intensity, which accounts for why it is prone to occur in closed syllables and longer words, and may receive stress only if the remaining vowel nuclei in the word are central and/or short peripheral. Moreover, variability in the F1 and F2 dimensions increases with the number of peripheral mid vowels, which appears to obey symmetry and dispersion principles of vowel space organization.

Complete Reduction to Amplitude Frequency Table (CRAFT)-A perspective.

The CRAFT (Complete Reduction to Amplitude Frequency Table) technique, based on Bayesian analysis approach, converts FID and/or interferogram (time domain) to a frequency-amplitude table (tabular domain) in a robust, automated, and time-efficient fashion. This mini review/perspective presents an introduction to CRAFT as a processing workflow followed by a discussion of several practical 1D and 2D examples of its applicability and associated benefit. CRAFT provides high quality quantitative results for complex systems without any need for conventional preprocessing steps, such as phase and baseline corrections. Two-dimensional time domain data are typically truncated, particularly in the evolution dimension, and conventional processing after zero-filling and t1max -matched apodization masks potentially available peak resolution. The line broadening introduced by extensive zero-filling and severe apodization functions leads to the lack of clear resolution of cross peaks. CRAFT decimation of interferograms, on the other hand, requires minimal or no apodization prior to extraction of the NMR parameters and significantly improves the spectral linewidth of the cross peaks along F1 dimension compared to conventional (FT) processing. The tabular representation of the CRAFT2d cross peaks information can be visualized in a variety of frequency domain formats for conventional spectral interpretation as well as quantitative applications. A simple workflow to generate in silico oversampled interferogram (iSOS) is presented, and its potential benefit in CRAFT decimation of highly crowded 2D NMR is demonstrated. This report is meant as a collective thesis to present a potentially new paradigm in data processing that questions the need for hitherto unchallenged preprocessing steps, such as phase and baseline correction in 1D and zero-fill/severe apodization in 2D.

Improving efficiency of measuring individual 1H coupling networks by pure shift 2D J-resolved NMR spectroscopy.

The 1H coupling networks, including 1H-1H correlation and J coupling values, provide the important information for structure elucidation and conformation analysis. However, the presence of a large number of couplings and the phase-twist lineshapes often prevents revealing 1H coupling networks. Here, we provide a clean absorption-mode 2D NMR method, SIMAJ (SImple Methods for 2D Absorption mode J-resolved spectrum), for a straightforward assignment and measurement of the coupling network involving the chosen proton. Relying on the pure shift element, 1H-1H couplings and chemical shift evolution are totally separately demonstrating along the F1 and F2 dimensions, respectively. Processing with a single experiment dataset and free of 45° spectral shearing, an absorption-mode 2D J-resolved spectrum can be reconstructed. Two pulse sequences were proposed as examples. The SIMAJ signal processing method will be a general procedure for obtaining absorption-mode lineshapes when analyzing the experiment datasets with chemical shifts and J coupling multiplets in the orthogonal dimensions. With excellent sensitivity, high spectral purity, and ability of easily identifying 1H-1H correlations, significant improvements are beneficial for structural, conformational, or complex composition analyses.

Pure shift HMQC: Resolution and sensitivity enhancement by bilinear rotation decoupling in the indirect and direct dimensions

The heteronuclear multiple-quantum coherence in the indirect dimension of the two-dimensional HMQC experiment evolves under the passive 1H-1H J-couplings leading to multiplet structures in the F1 dimension. Besides, 1H-1H J-multiplets appear in the direct dimension as well. Thus, multiplets along both dimensions lower the resolution and sensitivity of this technique, when high resolution is required along both dimensions. An efficient broadband homodecoupling scheme along the F1 dimension of the HMQC experiment has not been realized to date. We have implemented broadband homonuclear decoupling using bilinear rotation decoupling (BIRD) by adding a 1H SQ evolution period followed by BIRD before the 1H-13C multiple-quantum evolution period in the HMQC. In the direct time domain, BIRD is implemented using a real-time or single-scan scheme, which further improves resolution and sensitivity of this technique. The resulting pure shift HMQC provides singlet peak per chemical site along F1 as well as F2 axes and, hence, better resolution and sensitivity than conventional HMQC spectrum for all peaks except diastereotopic methylene protons. Due to the incorporation of the BIRD, the indirect time domain becomes double in length compared to the conventional HMQC. However, slow relaxation of small molecules favors better sensitivity for ps-HMQC relative to conventional HMQC under all conditions. We also found that the sensitivity of ps-HMQC is only slightly less than ps-HSQC for small molecules.

Psychometric Properties and Construct Validity of the Short Version of the Self-Report Psychopathy Scale in a Southern European Sample

The Self-Report Psychopathy Scale–Short Form (SRP–SF) is a brief measure of psychopathy, developed via model-based test theory. The SRP–SF has a 4-factor structure with items reflecting affective, interpersonal, lifestyle, and antisocial domains, in line with the Psychopathy Checklist–Revised (PCL–R), which can be aggregated to form the traditional F1 and F2 dimensions of psychopathy. Previous research indicates the SRP is a viable tool for examining the prevalence of psychopathic propensities and their correlates in nonoffender populations. Currently, a substantial amount of nonoffender research on psychopathy is conducted in North America. Here, we inspect the psychometric properties of the SRP–SF and probe its association with general personality and empathy in a large southern European (Portuguese) community sample. Consistent with previous studies, results indicated good fit for the 4-factor model, including for separate female and male subsamples, good internal consistency across its scales and subscales, and the predicted pattern of associations with the correlates of psychopathy. The results of this cross-cultural study provide further evidence of the validity of the SRP–SF in the assessment of psychopathy in community samples, and help to extend the nomological net on the larger construct to a southern European sample.

Accommodation of L2 Speech in a Repetition Task: Exploring Paralinguistic Imitation

Phonetic convergence is the process by which a speaker adapts his/her speech to sound more similar to his/her interlocutor. While most studies analysing this process have been conducted amongst speakers sharing the same language or variety, this experiment focuses on imitation between non-native and native speakers in a repetition task. The data is a fragment from the ANGLISH corpus designed by Anne Tortel (Tortel, 2008). 40 French speakers (10 male intermediate, 10 male advanced, 10 female intermediate and 10 female advanced learners) were asked to repeat a set of 20 sentences produced by British native speakers. Segmental (vowel quality), suprasegmental (vowel duration) and voice quality were analysed. Level of proficiency, gender and model talker were taken as independent variables. Level appeared not to be a relevant parameter due to a high amount of inter-individual variability amongst groups. Somewhat contradictory results were observed for vowel duration and F1-F2 distance for male learners converged more than female learners. Our hypothesis that low vowels display a higher degree of imitation, and especially within the F1 dimension (Babel, 2012), was partially validated. Convergence in vowel duration in order to sound more native-like was also observed (Zając, 2013). Regarding the analysis of voice quality, and more particularly of creaky voice, observations suggest that some advanced female learners creaked more than the native speakers and more in the reading task, which indicate, both linguistic idiosyncrasy and accommodation towards the native speakers. Low vowels seem also to be more likely to be produced with a creaky voice, especially at the end of prosodic constituents.

Patterns of the Mainstream Sound Change in a Liminal Region: Low Back Merger in Washington DC

This study investigates the low back vowel merger (lot-thought merger) of African American and European American speakers in Washington DC. The study aims to follow up with the previous investigation by Labov et al. (2006) on low back merger in DC, and investigate whether African American speakers in DC are participating in the merger, one of the majority-led sound changes. The study also examines the difference in low back vowel production between African Americans from a particular quadrant of the city, namely, Southeast (SE), and those from elsewhere in DC. Data are taken from forty sociolinguistic interviews with natives of DC. The vowels were analyzed acoustically, taking F1 and F2 measurements at three different points of a vowel. Both the F1 and the F2 dimensions of the low back vowels and the degree of overlap were examined. The degree of overlap was measured by calculating the Pillai score for each speaker, with duration and following environment taken into account. Results indicate that DC is conservatively participating in the merger, with European American speakers exhibiting higher degrees of overlap than African American speakers. An age effect is also observed, but only among African American speakers who are not from SE. The study further argues that the participation in the mainstream sound change by some African Americans can also be analyzed as convergence to the local white norm, and that this convergence is more likely to be carried out by African American speakers who are not from SE, a section of the city in which the contact between African American speakers and European American speakers is minimal.

Combining Fourier phase encoding and broadband inversion toward J-edited spectra

Nuclear magnetic resonance (NMR) spectra are often utilized for gathering accurate information relevant to molecular structures and composition assignments. In this study, we develop a homonuclear encoding approach based on imparting a discrete phase modulation of the targeted cross peaks, and combine it with a pure shift experiments (PSYCHE) based J-modulated scheme, providing simple 2D J-edited spectra for accurate measurement of scalar coupling networks. Chemical shifts and J coupling constants of protons coupled to the specific protons are demonstrated along the F2 and F1 dimensions, respectively. Polychromatic pulses by Fourier phase encoding were performed to simultaneously detect several coupling networks. Proton-proton scalar couplings are chosen by a polychromatic pulse and a PSYCHE element. Axis peaks and unwanted couplings are complete eradicated by incorporating a selective COSY block as a preparation period. The theoretical principles and the signal processing procedure are laid out, and experimental observations are rationalized on the basis of theoretical analyses.

Online Adaptation to Altered Auditory Feedback Is Predicted by Auditory Acuity and Not by Domain-General Executive Control Resources.

When a speaker's auditory feedback is altered, he adapts for the perturbation by altering his own production, which demonstrates the role of auditory feedback in speech motor control. In the present study, we explored the role of auditory acuity and executive control in this process. Based on the DIVA model and the major cognitive control models, we expected that higher auditory acuity, and better executive control skills would predict larger adaptation to the alteration. Thirty-six Spanish native speakers performed an altered auditory feedback experiment, executive control (numerical Stroop, Simon and Flanker) tasks, and auditory acuity tasks (loudness, pitch, and melody pattern discrimination). In the altered feedback experiment, participants had to produce the pseudoword “pep” (/pep/) while perceiving their auditory feedback in real time through earphones. The auditory feedback was first unaltered and then progressively altered in F1 and F2 dimensions until maximal alteration (F1 −150 Hz; F2 +300 Hz). The normalized distance of maximal adaptation ranged from 4 to 137 Hz (median of 75 ± 36). The different measures of auditory acuity were significant predictors of adaptation, while individual measures of cognitive function skills (obtained from the executive control tasks) were not. Better auditory discriminators adapted more to the alteration. We conclude that adaptation to altered auditory feedback is very well-predicted by general auditory acuity, as suggested by the DIVA model. In line with the framework of motor-control models, no specific claim on the implication of executive resources in speech motor control can be made.

(3, 2)D 1H, 13C BIRDr,X-HSQC-TOCSY for NMR structure elucidation of mixtures: application to complex carbohydrates

Overlap of NMR signals is the major cause of difficulties associated with NMR structure elucidation of molecules contained in complex mixtures. A 2D homonuclear correlation spectroscopy in particular suffers from low dispersion of 1H chemical shifts; larger dispersion of 13C chemical shifts is often used to reduce this overlap, while still providing the proton–proton correlation information e.g. in the form of a 2D 1H, 13C HSQC-TOCSY experiment. For this methodology to work, 13C chemical shift must be resolved. In case of 13C chemical shifts overlap, 1H chemical shifts can be used to achieve the desired resolution. The proposed (3, 2)D 1H, 13C BIRDr,X-HSQC-TOCSY experiment achieves this while preserving singlet character of cross peaks in the F1 dimension. The required high-resolution in the 13C dimension is thus retained, while the cross peak overlap occurring in a regular HSQC-TOCSY experiment is eliminated. The method is illustrated on the analysis of a complex carbohydrate mixture obtained by depolymerisation of a fucosylated chondroitin sulfate isolated from the body wall of the sea cucumber Holothuria forskali.

Highly resolved HSQC experiments for the fast and accurate measurement of homonuclear and heteronuclear coupling constants

A number of J-upscaled NMR experiments are currently available to measure coupling constants along the indirect F1 dimension of a 2D spectrum. A major drawback is the limited F1 digital resolution that requires long acquisition times in order to achieve reasonably accurate measures. Here is shown how high levels of F1 digital resolution in a multiple-purpose HSQC experiment can be easily achieved by implementing a general J/δ-scaling strategy. In particular, a set of new J-resolved HSQC experiments is presented for a faster and much more accurate J determination in small molecules. Several options and practical aspects are discussed and exemplified by measuring the magnitude and/or the sign of several homo- and heteronuclear coupling constants in one shot.

2JHH-resolved HSQC: Exclusive determination of geminal proton-proton coupling constants

The measurement of two-bond proton-proton coupling constants (2JHH) in prochiral CH2 groups from the F2 dimension of 2D spectra is not easy due to the usual presence of complex multiplet J patterns, line broadening effects and strong coupling artifacts. These drawbacks are particularly pronounced and frequent in AB spin systems, as those normally exhibited by the pair of diastereotopic CH2 protons. Here, a novel 2JHH-resolved HSQC experiment for the exclusive and accurate determination of the magnitude of 2JHH from the doublet displayed along the highly-resolved indirect F1 dimension is described. A pragmatic 2JHH NMR profile affords a fast overview of the full range of existing 2JHH values. In addition, a 2JHH/δ(13C)-scaled version proves to be an efficient solution when severe signal overlapping complicate a rigorous analysis. The performance of the method is compared with other current techniques and illustrated by the determination of challenging residual dipolar 2DHH coupling constants of small molecules dissolved in weakly orienting media.

Perfect 1JCH-resolved HSQC: Efficient measurement of one-bond proton-carbon coupling constants along the indirect dimension

A versatile 1JCH-resolved HSQC pulse scheme for the speedy, accurate and automated determination of one-bond proton-carbon coupling constants is reported. The implementation of a perfectBIRD element allows a straightforward measurement from the clean doublets obtained along the highly resolved F1 dimension, even for each individual 1JCHa and 1JCHb in diastereotopic HaCHb methylene groups. Real-time homodecoupling during acquisition and other alternatives to minimize accidental signal overlapping in overcrowded spectra are also discussed.

Real time band selective F1 -decoupled proton NMR for the demixing of overlay spectra of chiral molecules.

The small chemical shift dispersion and complex multiplicity pattern in proton NMR limit quantifications, for instance the determination of enantiomeric excess (ee) for an enantiomeric mixture. Herein, we present a simple proton-proton correlation experiment with band selective homonuclear (BASH) decoupling in both F1 and F2 dimensions, for the removal of scalar and residual dipolar couplings to provide collapsed singlet for each chemical site. The method has been demonstrated to separate the severely overlapped spectra of enantiomers using both chiral isotropic and anisotropic phases as well as a small biomolecule, particularly for the diastereotopic protons and also for the determination of ee. Copyright © 2016 John Wiley & Sons, Ltd.