Impacts on Speech Features of Body Positions

Abstract

Speech sounds are fundamental to human communication, and speech production allows people to express intentions. The speech can be produced in any position, such as lying, sitting, and standing. These positions have been suggested to affect the tissues and organs inside the human body, including the tissues used to produce speech, which might influence speech features, for instance, the vocal tract. The analysis of acoustic speech features in this thesis is based on recordings of speakers in three postures (lying supine, sitting, and standing) and will be carried out to investigate whether the body positions affect the speech features or not. Two databases examined in this research include the hVd isolated word database and the passage database, based on nine New Zealand English speakers and one British English speaker. The speakers are in different age ranges and genders to divide into groups, as age and gender are important factors that have been suggested to affect the speech features. The analysis focuses on the vowels, while formants are a critical element of the study. This thesis calculated and analyzed the first (F1) and second (F2) formant frequencies to address the research question. The fundamental (F0) frequency and vowel duration were also examined to explore the impact of body positions on speech features. The acoustic measurements examine the effects of the three postures. The analysis revealed that posture-related effects were observed in the speech features that have been focused on, with distinct impacts observed based on age, gender, and vowel type. Older speakers contained more variation in formant frequencies in the lying position than the sitting or standing. Significant differences in formant frequencies and duration occurred for distinct vowels across the three postures. In short, this thesis demonstrates the necessity of considering the position effect while analyzing speech and discusses the posture-related effects on the speech features in the results.