The Sound of Sleepiness
A 24-hour sleep deprivation experiment, examining the relationship between Acoustic Vowel Space and sleepiness in sleep-deprived, Danish-speaking individuals.
Keywords:
Acoustic Vowel Space (AVS), Vowel Space Area (VSA), Sleep-deprivation, Danish, Linguistics, Experimental PhoneticsAbstract
This study investigates the impact of short-term sleep deprivation on Acoustic Vowel Space (AVS), hypothesizing that Vowel Space Area (VSA) will shrink, with a more pronounced correlation with sleepiness, rather than simply the duration of wakefulness. Sleepiness levels were assessed using the Karolinska Sleepiness Scale, reaction time measurements, and performance in a memory task. Phonetic data were collected through semi-spontaneous speech tasks, using picture descriptions recorded in a controlled sound studio environment. Twelve native Danish speakers (aged 20–30) were monitored over a 24-hour period, with data collected at six-hour intervals. Variables such as individual sleep habits, substance use, and environmental influences were controlled for to ensure reliable results. On average, VSA decreased by 14.23% (p_adj =0.025) after 24 hours of wakefulness compared to baseline (after 6 wakeful hours), with 11 of 12 participants showing an overall reduction. Significant correlations were found between normalized VSA and two sleepiness markers: reaction time (p = 0.010) and self-reported sleepiness (p = 0.002), but not with memory-based markers. Notably, VSA correlated more strongly with hours awake past participants’ usual bedtime (p = 0.000943) than with total hours awake (p = 0.0014), suggesting a hypoarticulatory sleepinessrelated effect, rather than one driven by vocal fatigue.
References
Akerstedt T, Gillberg M. (1990). Subjective and objective sleepiness in the active individual. International Journal of Neuroscience, 52, 29–37. https://doi.org/10.3109/00207459008994241
Baker, A., Mielke, J., & Archangeli, D. (2008). More velar than /ɡ/: Consonant coarticulation as a cause of diphthongization. In C. B. Chang & H. J. Haynie (Eds.), Proceedings of the 26th West Coast Conference on Formal Linguistics, 60-68. Somerville, MA: Cascadilla Proceedings Project. https://www.lingref.com/cpp/wccfl/26/paper1656.pdf
Bryan, L., & Guo, L. (2024, March 15). Circadian rhythm. Sleep Foundation. https://www.sleepfoundation.org/circadian-rhythm
Ejstrup, M., & Hansen, G. F. (2004a). Vokaler I tre regionale varianter af Dansk. Master’s Thesis, University of Copenhagen, 7-100.
Ejstrup, M., & Hansen, G. F. (2004b). Vowels in regional variants of Danish. Proceedings FONETIK 2004, Stockholm University, 88-91. https://www.diva-portal.org/smash/get/diva2:176795/FULLTEXT01.pdf#page=88
Ekrem, D. (2022). Why You Can’t Remember Where Your Keys Are: The Effects of Sleep Deprivation on Visual Short-Term Memory. International Journal of High School Research, 4(4), 36–39. https://doi.org/10.36838/v4i4.7
Fox, R. A., & Jacewicz, E. (2017). Reconceptualizing the vowel space in analyzing regional dialect variation and sound change in American English. The Journal of the Acoustical Society of America, 142(1), 444–459. https://doi.org/10.1121/1.4991021
Grønnum, N. (2022). Conventions for segmental transcription. DanPASS. https://www.danpass.hum.ku.dk/links_2014/conventions/segmental_transcription.pdf
Hansen, G. (2024). Whisper in Praat v0.8.2 (Windows & macOS). http://dx.doi.org/10.13140/RG.2.2.24093.93925
Kuo, C., & Berry, J. (2023). The Relationship Between Acoustic and Kinematic Vowel Space Areas With and Without Normalization for Speakers With and Without Dysarthria. American Journal of Speech-Language Pathology, 32(4S). https://doi.org/10.1044/2023_AJSLP-22-00158
Lee, H., Song, H., Ham, B., Suh, K., & Kim, L. (2001). Effects of total sleep deprivation on fine motor performance. Sleep Medicine and Psychophysiology, 8(2), 129–137. https://www.koreascience.or.kr/article/JAKO200115750715092.pdf
Lindquist, J. (2023). Supplerende forsøgsforslag: Effekten af kortvarig søvndeprivation på akustiske parametre for sibilanter. Unpublished exam, Akustisk Analyse E23, University of Copenhagen.
Miley, A. Å., Kecklund, G., & Åkerstedt, T. (2016). Comparing two versions of the Karolinska Sleepiness Scale (KSS). Sleep and Biological Rhythms, 14(3), 257–260. https://doi.org/10.1007/s41105-016-0048-8
Nathan, G. S., Ladefoged, P., & Maddieson, I. (1998). The Sounds of the World’s Languages. Language, 74(2), 313. https://doi.org/10.2307/417875
OpenAI. (2022). Whisper AI: Speech recognition model.
R Core Team. (2021). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
Rusz, J., Vaneckova, M., Benova, B., Tykalova, T., Novotny, M., Ruzickova, H., Uher, T., Andelova, M., Novotna, K., Friedova, L., Motyl, J., Kucerova, K., Krasensky, J., & Horakova, D. (2019). Brain volumetric correlates of dysarthria in multiple sclerosis. Brain and Language, 194, 58–64. https://doi.org/10.1016/j.bandl.2019.04.009
Schachtenhaufen, R. (2023). Utilpasset IPA. Danske Studier, 48-49. https://doi.org/10.7146/danskestudier.vi2023.146735
Shahid, A., Wilkinson, K., Marcu, S., & Shapiro, C. M. (2011). Karolinska Sleepiness Scale (KSS). STOP, THAT and One Hundred Other Sleep Scales, 209–210. https://doi.org/10.1007/978-1-4419-9893-4_2
Thoret, E., Andrillon, T., Gauriau, C., Léger, D., & Pressnitzer, D. (2024). Sleep deprivation detected by voice analysis. PLOS Computational Biology, 20(2), e1011849–e1011849. https://doi.org/10.1371/journal.pcbi.1011849
Tukey, J. W. (1949). Comparing individual means in the analysis of variance. Biometrics, 5(2), 99–114. https://doi.org/10.2307/3001913
Warthe, A. B., & Sharma, V. (2022). Changes in speech and voice characteristics following two hours and eight hours of acute sleep deprivation. Indian Journal of Aerospace Medicine, 66, 15–20. https://doi.org/10.25259/ijam_18_2020
Weirich, M., & Simpson, A. P. (2023). Changes in parents’ phonetic parameters during the first year of a child’s life. Comparative study of German and Swedish, Proceedings of the 20th ICPhS, 1-5. https://www.internationalphoneticassociation.org/icphs-proceedings/ICPhS2023/full_papers/54.pdf
Zeller, C. (1997). The investigation of a sound change in progress: /æ/ to /e/ in Midwestern American English. Journal of English Linguistics, 25(2), 142-155. https://doi.org/10.1177/007542429702500207
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