Voiceless fricatives are articulatorily and acoustically complex, and relatively late acquired by children. There are a plenitude of descriptions of voiceless fricatives in other languages, which have revealed language-specific patterns in realisation and acquisition. However, studies of Swedish adult’s voiceless fricatives are dated and small-scale, and knowledge concerning Swedish children’s acquisition of these complex sounds is limited.

This dissertation is based on four papers, three of which investigate acoustic characteristics of adult and child productions of Swedish voiceless fricatives /f, s, ɕ, ɧ/. Static and dynamic, individual and group-level acoustic patterns (primarily spectral features) are described, and between-fricative contrasts are quantified for individual speakers. The fourth paper explores the influence of lexical context and experience on perceptual ratings of children’s voiceless sibilant fricatives /s, ɕ/. Specifically, listeners with and without clinical experience of assessing child speech (i.e., speech-language pathologists and laypeople) provided gradient ratings of sibilants presented in lexical and non-lexical contexts (i.e., words or CV-syllables).

This work contributes to a better understanding of the characteristics and variability of /f, s, ɕ, ɧ/, and provides new insights into children’s acquisition of voiceless fricatives. A number of spectral parameters and statistical models were utilised in this work. The results of the fourth study also have relevance for perceptual assessments of speech in the clinic.