Browsing by Subject "tila-akustiikka"

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  • Asikainen, Atte (Helsingin yliopisto, 2021)
    It is common for speech to occur in closed spaces. Hence, room acoustics have a significant role in speech communication. In previous studies, effects of reverberation on speech production have been found. However, research on the concerned field is yet scarce. Adverse room acoustics have been observed to expose occupational speakers, such as teachers, to voice disorders. Thus, it is crucial to study what are the room acoustic requirements for economic speaking. The purpose of this study is to examine which speech-acoustic traits change when the speaker is exposed to reverberation, and how. In the present study, two different approaches are taken: variation of reverberation time and removal of the reverberation. The changes in speech are reflected to the Lombard sign (the raise of speech level in a noisy environment). Additionally, differences related to gender and prosody are examined concerning the present topic. In this study, a speech production experiment was conducted with acoustic and statistical analyses. 11 Finnish-speaking volunteers (six females and five males) participated the experiment, where 150 short sentences were recorded from each participant. The sentences were produced in five different room-acoustic conditions. In four out of five, digitally simulated reverberation was played back on headphones worn by the participant with varying reverberation times. The fifth condition was (nearly) anechoic. Out of the recorded sentences, speech rate, creak ratio and harmonics-to-noise ratio were measured along with mean, maximum and movement of intensity and pitch. The measurements were then assessed with various statistical methods. The results of the study show a significant decrease in speech rate caused by an increasing reverberation time. Additionally, speech rate was the highest in the anechoic condition. Moreover, creak ratio decreased greatly when reverberation time increased to more than one second especially on male speakers and end-weighted sentences. Additionally, monotonousness was higher in reverberated conditions than the anechoic condition. However, substantial speaker-dependent differences in the effects of reverberation on speech were found. Moreover, sentence weight was found to influence speech more fundamentally than reverberation. The results suggest that rooms with average reverberation times, rather than particularly long or short, seem the most beneficial for speaking. This observation corresponds to previous studies. Further research on the field is required to extract valuable knowledge needed in acoustical design of spaces, including classrooms. Designing speaker-friendly spaces helps to preserve occupational speakers’ voices throughout their careers.