Descriptions of the acoustic characteristics of Swedish voiceless fricatives are scarce and are limited to static measures derived from the speech of a small number of speakers. The current study provides an updated acoustic description of the static (spectral, temporal, and intensity) characteristics of word-initial voiceless fricatives in Central Standard Swedish. In addition, temporal variation of spectral centre of gravity is modelled using a generalized additive mixed model. Results show that fricatives were differentiated in terms of spectral properties, duration, and intensity level, such that sibilant fricatives were generally longer and more intense than non-sibilant fricatives. Spectral centre of gravity differentiated between all places of articulation apart from labio-dental /f/. Gender differences were found for centre of gravity in /s/ but overall, sex/gender differences were small. Dynamic analyses revealed differences in curvature as well as overall level of spectral centre of gravity across the duration of the fricative, associated with place of articulation and mediated by vowel context, fricative duration, and speaker specific patterns. The results from the present study are valuable for future cross-linguistic research, and as reference for investigations concerning children's acquisition of Swedish voiceless fricatives.

In this study, we explore individual variation and contrast in Swedish children’s voiceless fricatives. Thirty-one children between three and eight years of age participated in a picture-prompted word repetition task, wherein they repeated fricative-initial words in a variety of vowel contexts. The fricatives were transcribed and acoustically analysed, using spectral moments 1–4, spectral peak and spectral balance measures. Random forests were used to estimate the relative importance of each spectral feature in the classification of correct fricative productions, as well as to measure robustness of the late-emerging contrast between sibilants [s] and [ɕ] in individual children. Transcription analysis revealed that substitutions involving a more anterior place of articulation were common. Acoustic analysis showed individual differences in variability and contrast in the children’s fricative systems across and within age groups. Cue weighting of spectral characteristics in classification was similar in all age groups for correct productions, while the magnitude of the acoustic contrast between sibilants increased with age. This paper provides a description of individual variation in Swedish children’s acquisition of fricatives which can inform future large-scale speech-acquisition research.