This study compared the acoustic properties of 26 (100% female, 100% monolingual) Danish caregivers' spontaneous speech addressed to their 11- to 24-month-old infants (infant-directed speech, IDS) and an adult experimenter (adult-directed speech, ADS). The data were collected between 2016 and 2018 in Aarhus, Denmark. Prosodic properties of Danish…

There is a long-standing debate in the literature about the benefits that acoustic components of Infant Directed Speech (IDS) might have for infants' language acquisition. One of the highly contested features is vowel space expansion, which refers to the enlargement of the acoustic space between the corner vowels /i, u, a/ in IDS compared to Adult…

Background: Previous research has found that high-frequency energy of speech signals decreased while wearing face masks. However, no study has examined the specific spectral characteristics of fricative consonants and vowels and the perception of clarity of speech in mask wearing. Aims: To investigate acoustic-phonetic characteristics of fricative…

Purpose: Current models of speech development argue for an early link between speech production and perception in infants. Recent data show that young infants (at 4-6 months) preferentially attend to speech sounds (vowels) with infant vocal properties compared to those with adult vocal properties, suggesting the presence of special "memory…

Purpose: Envelope following responses (EFRs) could be useful for objectively evaluating audibility of speech in children who are unable to participate in routine clinical tests. However, relative to adults, the characteristics of EFRs elicited by frequency-specific speech and their utility in predicting audibility in children are unknown. Method:…

Purpose: The objective of this study was to determine if and how the subcortical neural representation of pitch cues in listeners with normal hearing is affected by systematic manipulation of vocoder parameters. Method: This study assessed the effects of temporal envelope cutoff frequency (50 and 500 Hz), number of channels (1-32), and carrier…

Although second language (L2) learners often have difficulty with learning the L2 pronunciation, the literature has reported a mix of more successful and less successful learners. Many factors could contribute to individual variation in L2 speech sound learning. This dissertation examines a few factors that are hypothesized to influence L2…

Purpose: The goal of this study was to explore the relationships among vocal effort, extrinsic laryngeal muscle activity, and vocal tract length (VTL) within healthy speakers. We hypothesized that increased vocal effort would result in increased suprahyoid muscle activation and decreased VTL, as previously observed in individuals with vocal…

Purpose: This study investigated vowel and sibilant productions in noise to determine whether responses to noise (a) are sensitive to the spectral characteristics of the noise signal and (b) are modulated by the contribution of vowel or sibilant contrasts to word discrimination. Method: Vowel and sibilant productions were elicited during serial…

The goal of this dissertation is to better understand the targets of vowels in speech production. Three experiments investigate vowel production in non-native speech, probing how new vowel categories, and thus targets, are formed. Three research questions are addressed: (1) Do vowels have articulatory targets (as predicted by Browman &…

Speech is highly variable and systematic, governed by the internal linguistic system and socio-indexical factors. The systematic relationship of socio-indexical factors and variable phonetic forms, referred to here as "socio-indexical structure," has been the cornerstone of sociophonetic research over the last several decades. Research…

Purpose: The purpose of this study was to investigate how general, implicit instructions with auditory-perceptual emphasis; specific, explicit instructions with biomechanical focus; or both affect learning of oral-nasal balance control in speech. Method: Thirty healthy, vocally untrained participants were assigned to one of three instructional…

Purpose: This study examined the speech acoustic characteristics of Jamaican Creole (JC) and English in bilingual preschoolers and adults using acoustic duration measures. The aims were to determine if, for JC and English, (a) child and adult acoustic duration characteristics differ, (b) differences occur in preschoolers' duration patterns based…

Purpose: Individuals with cerebellar ataxia (CA) caused by cerebellar degeneration exhibit larger reactive compensatory responses to unexpected auditory feedback perturbations than neurobiologically typical speakers, suggesting they may rely more on feedback control during speech. We test this hypothesis by examining variability in unaltered…

Individual differences in infants' native phonological development have been linked to the quantity and quality of infant-directed speech (IDS). The effects of parental and infant bilingualism on this relation in 131 five- and nine-month-old monolingual and bilingual Spanish and Basque infants (72 male; 59 female; from white middle-class…