It has been claimed that the long established neutralization of the voicing distinction in domain final position in German is phonetically incomplete. However, various studies leading to this claim have been criticized in terms of their methodology. In three production experiments and one perception experiment we address these methodological criticisms. In the first production study, we address the role of orthography. In a large scale auditory task using pseudowords, we confirm that neutralization is indeed incomplete and suggest that previous null results may simply be due to lack of statistical power. In two follow-up production studies (experiments 2 and 3), we rule out a potential confound of experiment 1, namely that the effect might be due to accommodation to the presented auditory stimuli. Here we bias the auditory stimuli against the phenomenon by manipulating the duration of the preceding vowel. While experiment 2 replicated our findings, experiment 3 failed to replicate incomplete neutralization statistically, even though we found numerical tendencies into the expected direction. Finally, in a perception study (experiment 4), we demonstrate that the subphonemic differences between final voiceless and "devoiced" stops are audible, but only barely so. Even though the present findings provide evidence for incomplete neutralization, the small effect sizes obtained further highlight the limits of investigating incomplete neutralization emphasizing the limited importance of this phenomenon for everyday speech communication. We argue that without postulating functional relevance, incomplete neutralization can be accounted for by recent models of lexical organization and is compatible with formal phonological models that entertain unpronounced projection relations.

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Many drum communication systems around the world transmit information by emulating tonal and rhythmic patterns of spoken languages in sequences of drumbeats. Their rhythmic characteristics, in particular, have not been systematically studied so far, although understanding them represents a rare occasion for providing an original insight into the basic units of speech rhythm as selected by natural speech practices directly based on beats. Here, we analyse a corpus of Bora drum communication from the northwest Amazon, which is nowadays endangered with extinction. We show that four rhythmic units are encoded in the length of pauses between beats. We argue that these units correspond to vowel-to-vowel intervals with different numbers of consonants and vowel lengths. By contrast, aligning beats with syllables, mora or only vowel length yields inconsistent results. Moreover, we also show that Bora drummed messages conventionally select rhythmically distinct markers to further distinguish words. The two phonological tones represented in drummed speech encode only few lexical contrasts. Rhythm thus appears to crucially contribute to the intelligibility of drummed Bora. Our study provides novel evidence for the role of rhythmic structures composed of vowel-to-vowel intervals in the complex puzzle concerning the redundancy and distinctiveness of acoustic features embedded in speech.

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The origins of human speech are obscure; it is still unclear what aspects are unique to our species or shared with our evolutionary cousins, in part due to a lack of a common framework for comparison. We asked what chimpanzee and human vocal production acoustics have in common. We examined visible supra-laryngeal articulators of four major chimpanzee vocalizations (hoos, grunts, barks, screams) and their associated acoustic structures, using techniques from human phonetic and animal communication analysis. Data were collected from wild adult chimpanzees, Taï National Park, Ivory Coast. Both discriminant and principal component classification procedures revealed classification of call types. Discriminating acoustic features include voice quality and formant structure, mirroring phonetic features in human speech. Chimpanzee lip and jaw articulation variables also offered similar discrimination of call types. Formant maps distinguished call types with different vowel-like sounds. Comparing our results with published primate data, humans show less F1–F2 correlation and further expansion of the vowel space, particularly for [i] sounds. Unlike recent studies suggesting monkeys achieve human vowel space, we conclude from our results that supra-laryngeal articulatory capacities show moderate evolutionary change, with vowel space expansion continuing through hominoid evolution. Studies on more primate species will be required to substantiate this. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part II)’.

The widely cited frequency code hypothesis attempts to explain a diverse range of communicative phenomena through the acoustic projection of body size. The set of phenomena includes size sound symbolism (using /i/ to signal smallness in words such as teeny ), intonational phonology (using rising contours to signal questions) and the indexing of social relations via vocal modulation, such as lowering one's voice pitch to signal dominance. Among other things, the frequency code is commonly interpreted to suggest that polite speech should be universally signalled via high pitch owing to the association of high pitch with small size and submissiveness. We present a cross-cultural meta-analysis of polite speech of 101 speakers from seven different languages. While we find evidence for cross-cultural variation, voice pitch is on average lower when speakers speak politely, contrary to what the frequency code predicts. We interpret our findings in the light of the fact that pitch has a multiplicity of possible communicative meanings. Cultural and contextual variation determines which specific meanings become manifest in a specific interactional context. We use the evidence from our meta-analysis to propose an updated view of the frequency code hypothesis that is based on the existence of many-to-many mappings between speech acoustics and communicative interpretations. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.