Fundamental frequency (fo), perceived as voice pitch, is the most sexually dimorphic, perceptually salient and intensively studied voice parameter in human nonverbal communication. Thousands of studies have linked human fo to biological and social speaker traits and life outcomes, from reproductive to economic. Critically, researchers have used myriad speech stimuli to measure fo and infer its functional relevance, from individual vowels to longer bouts of spontaneous speech. Here, we acoustically analysed fo in nearly 1000 affectively neutral speech utterances (vowels, words, counting, greetings, read paragraphs and free spontaneous speech) produced by the same 154 men and women, aged 18-67, with two aims: first, to test the methodological validity of comparing fo measures from diverse speech stimuli, and second, to test the prediction that the vast inter-individual differences in habitual fo found between same-sex adults are preserved across speech types. Indeed, despite differences in linguistic content, duration, scripted or spontan--eous production and within-individual variability, we show that 42-81% of inter-individual differences in fo can be explained between any two speech types. Beyond methodological implications, together with recent evidence that inter-individual differences in fo are remarkably stable across the lifespan and generalize to emotional speech and nonverbal vocalizations, our results further substantiate voice pitch as a robust and reliable biomarker in human communication.
Keywords: fundamental frequency; nonverbal communication; sexual selection; source-filter theory; speech.