Production and perception of Libyan Arabic vowels

PhD ThesisThis study investigates the production and perception of Libyan Arabic (LA) vowels by native speakers and the relation between these major aspects of speech. The aim was to provide a detailed acoustic and auditory description of the vowels available in the LA inventory and to compare the phonetic features of these vowels with those of other Arabic varieties. A review of the relevant literature showed that the LA dialect has not been investigated experimentally. The small number of studies conducted in the last few decades have been based mainly on impressionistic accounts. This study consists of two main investigations: one concerned with vowel production and the other with vowel perception. In terms of production, the study focused on gathering the data necessary to define the vowel inventory of the dialect and to explore the qualitative and quantitative characteristics of the vowels contained in this inventory. Twenty native speakers of LA were recorded while reading target monosyllabic words in carrier sentences. Acoustic and auditory analyses were used in order to provide a fairly comprehensive and objective description of the vocalic system of LA. The results showed that phonologically short and long Arabic vowels vary significantly in quality as well as quantity; a finding which is increasingly being reported in experimental studies of other Arabic dialects. Short vowels in LA tend to be more centralised than has been reported for other Arabic vowels, especially with regards to short /a/. The study also looked at the effect of voicing in neighbouring consonants and vowel height on vowel duration, and the findings were compared to those of other varieties/languages. The perception part of the study explored the extent to which listeners use the same acoustic cues of length and quality in vowel perception that are evident in their production. This involved the use of continua from synthesised vowels which varied along duration and/or formant frequency dimensions. The continua were randomised and played to 20 native listeners who took part in an identification task. The results show that, when it comes to perception, Arabic listeners still rely mainly on quantity for the distinction between phonologically long and short vowels. That is, when presented with stimuli containing conflicting acoustic cues (formant frequencies that are typical of long vowels but with short duration or formant frequencies that are typical of short vowels but with long duration), listeners reacted consistently to duration rather than formant frequency. The results of both parts of the study provided some understanding of the LA vowel system. The production data allowed for a detailed description of the phonetic characteristics of LA vowels, and the acoustic space that they occupy was compared with those of other Arabic varieties. The perception data showed that production and perception do not always go hand in hand and that primary acoustic cues for the identification of vowels are dialect- and language-specific

Asymmetric discrimination of non-speech tonal analogues of vowels

Published in final edited form as: J Exp Psychol Hum Percept Perform. 2019 February ; 45(2): 285–300. doi:10.1037/xhp0000603.Directional asymmetries reveal a universal bias in vowel perception favoring extreme vocalic articulations, which lead to acoustic vowel signals with dynamic formant trajectories and well-defined spectral prominences due to the convergence of adjacent formants. The present experiments investigated whether this bias reflects speech-specific processes or general properties of spectral processing in the auditory system. Toward this end, we examined whether analogous asymmetries in perception arise with non-speech tonal analogues that approximate some of the dynamic and static spectral characteristics of naturally-produced /u/ vowels executed with more versus less extreme lip gestures. We found a qualitatively similar but weaker directional effect with two-component tones varying in both the dynamic changes and proximity of their spectral energies. In subsequent experiments, we pinned down the phenomenon using tones that varied in one or both of these two acoustic characteristics. We found comparable asymmetries with tones that differed exclusively in their spectral dynamics, and no asymmetries with tones that differed exclusively in their spectral proximity or both spectral features. We interpret these findings as evidence that dynamic spectral changes are a critical cue for eliciting asymmetries in non-speech tone perception, but that the potential contribution of general auditory processes to asymmetries in vowel perception is limited.Accepted manuscrip

Forming New Vowel Categories in Second Language Speech: The Case of Polish Learners' Production of English /I/ and /e/

The paper concentrates on formation of L2 English vowel categories in the speech of Polish learners. More specifically, it compares distribution of two English categories - /I/ and /e/ relative to neighbouring Polish vowels. 43 participants recorded Polish and English vowels in a /bVt/ context. First two formants were measured at a vowel midpoint and plotted on a vowel plane. The results reveal that while a separate /I/ category is formed fairly effectively in Polish learners pronunciation of English, a category of /e/ is almost completely subsumed by a Polish vowel /ϵ

Listeners normalize speech for contextual speech rate even without an explicit recognition task

Speech can be produced at different rates. Listeners take this rate variation into account by normalizing vowel duration for contextual speech rate: An ambiguous Dutch word /m?t/ is perceived as short /mAt/ when embedded in a slow context, but long /ma:t/ in a fast context. Whilst some have argued that this rate normalization involves low-level automatic perceptual processing, there is also evidence that it arises at higher-level cognitive processing stages, such as decision making. Prior research on rate-dependent speech perception has only used explicit recognition tasks to investigate the phenomenon, involving both perceptual processing and decision making. This study tested whether speech rate normalization can be observed without explicit decision making, using a cross-modal repetition priming paradigm. Results show that a fast precursor sentence makes an embedded ambiguous prime (/m?t/) sound (implicitly) more /a:/-like, facilitating lexical access to the long target word "maat" in a (explicit) lexical decision task. This result suggests that rate normalization is automatic, taking place even in the absence of an explicit recognition task. Thus, rate normalization is placed within the realm of everyday spoken conversation, where explicit categorization of ambiguous sounds is rare

Verification of feature regions for stops and fricatives in natural speech

The presence of acoustic cues and their importance in speech perception have long remained debatable topics. In spite of several studies that exist in this eld, very little is known about what exactly humans perceive in speech. This research takes a novel approach towards understanding speech perception. A new method, named three-dimensional deep search (3DDS), was developed to explore the perceptual cues of 16 consonant-vowel (CV) syllables, namely /pa/, /ta/, /ka/, /ba/, /da/, /ga/, /fa/, /Ta/, /sa/, /Sa/, /va/, /Da/, /za/, /Za/, from naturally produced speech. A veri cation experiment was then conducted to further verify the ndings of the 3DDS method. For this pur- pose, the time-frequency coordinate that de nes each CV was ltered out using the short-time Fourier transform (STFT), and perceptual tests were then conducted. A comparison between unmodi ed speech sounds and those without the acoustic cues was made. In most of the cases, the scores dropped from 100% to chance levels even at 12 dB SNR. This clearly emphasizes the importance of features in identifying each CV. The results con rm earlier ndings that stops are characterized by a short-duration burst preceding the vowel by 10 cs in the unvoiced case, and appearing almost coincident with the vowel in the voiced case. As has been previously hypothesized, we con rmed that the F2 transition plays no signi cant role in consonant identi cation. 3DDS analysis labels the /sa/ and /za/ perceptual features as an intense frication noise around 4 kHz, preceding the vowel by 15{20 cs, with the /za/ feature being around 5 cs shorter in duration than that of /sa/; the /Sa/ and /Za/ events are found to be frication energy near 2 kHz, preceding the vowel by 17{20 cs. /fa/ has a relatively weak burst and frication energy over a wide-band including 2{6 kHz, while /va/ has a cue in the 1.5 kHz mid-frequency region preceding the vowel by 7{10 cs. New information is established regarding /Da/ and /Ta/, especially with regards to the nature of their signi cant confusions

English-learning infants’ perception of word stress patterns

Adult speakers of different free stress languages (e.g., English, Spanish) differ both in their sensitivity to lexical stress and in their processing of suprasegmental and vowel quality cues to stress. In a head-turn preference experiment with a familiarization phase, both 8-month-old and 12-month-old English-learning infants discriminated between initial stress and final stress among lists of Spanish-spoken disyllabic nonwords that were segmentally varied (e.g. [ˈnila, ˈtuli] vs [luˈta, puˈki]). This is evidence that English-learning infants are sensitive to lexical stress patterns, instantiated primarily by suprasegmental cues, during the second half of the first year of life

Acoustic Features and Perceptive Cues of Songs and Dialogues in Whistled Speech: Convergences with Sung Speech

Whistled speech is a little studied local use of language shaped by several cultures of the world either for distant dialogues or for rendering traditional songs. This practice consists of an emulation of the voice thanks to a simple modulated pitch. It is therefore the result of a transformation of the vocal signal that implies simplifications in the frequency domain. The whistlers adapt their productions to the way each language combines the qualities of height perceived simultaneously by the human ear in the complex frequency spectrum of the spoken or sung voice (pitch, timbre). As a consequence, this practice underlines key acoustic cues for the intelligibility of the concerned languages. The present study provides an analysis of the acoustic and phonetic features selected by whistled speech in several traditions either in purely oral whistles (Spanish, Turkish, Mazatec) or in whistles produced with an instrument like a leaf (Akha, Hmong). It underlines the convergences with the strategies of the singing voice to reach the audience or to render the phonetic information carried by the vowel (tone, identity) and some aesthetic effects like ornamentation

The listening talker: A review of human and algorithmic context-induced modifications of speech

International audienceSpeech output technology is finding widespread application, including in scenarios where intelligibility might be compromised - at least for some listeners - by adverse conditions. Unlike most current algorithms, talkers continually adapt their speech patterns as a response to the immediate context of spoken communication, where the type of interlocutor and the environment are the dominant situational factors influencing speech production. Observations of talker behaviour can motivate the design of more robust speech output algorithms. Starting with a listener-oriented categorisation of possible goals for speech modification, this review article summarises the extensive set of behavioural findings related to human speech modification, identifies which factors appear to be beneficial, and goes on to examine previous computational attempts to improve intelligibility in noise. The review concludes by tabulating 46 speech modifications, many of which have yet to be perceptually or algorithmically evaluated. Consequently, the review provides a roadmap for future work in improving the robustness of speech output