The Effects of Stress Type, Vowel Identity, Baseline f 0 , and Loudness on the Relative Fundamental Frequency of Individuals With Healthy Voices

Summary Objective Relative fundamental frequency (RFF) has been investigated as a possible acoustic measure to assess laryngeal tension. This study aimed to identify possible factors in RFF stimuli (stress type, vowel identity, baseline f 0 , and loudness) that might also affect RFF values. Methods Fifteen speakers with healthy voices produced short RFF stimuli (vowel-/f/-vowel; eg, /ɑfɑ/) in different conditions. They produced the stimuli with three different stress types and four different vowels. Participants also produced stimuli in three different baseline f 0 conditions and three different loudness conditions. The mean RFF and within- and between-subject standard deviation (SD) of RFF were estimated for each stimuli condition. Results Stress type had a statistically significant effect on RFF means and within-subject SDs with a large effect size ( P P 0 had a significant effect on RFF values with a medium effect size ( P Conclusions This evidence suggests that stress type is the most important factor to consider in RFF measurement. We also conclude that RFF may be somewhat resistant to vowel variation and small differences in baseline f 0 and loudness, which may be beneficial in clinical settings.