Predicting strength from aggressive vocalizations versus speech in African bushland and urban communities

The human voice carries information about a vocalizer's physical strength that listeners can perceive and that may influence mate choice and intrasexual competition. Yet, reliable acoustic correlates of strength in human speech remain unclear. Compared to speech, aggressive nonverbal vocalizations (roars) may function to maximize perceived strength, suggesting that their acoustic structure has been selected to communicate formidability, similar to the vocal threat displays of other animals. Here, we test this prediction in two non-WEIRD African samples: an urban community of Cameroonians and rural nomadic Hadza hunter–gatherers in the Tanzanian bushlands. Participants produced standardized speech and volitional roars and provided handgrip strength measures. Using acoustic analysis and information-theoretic multi-model inference and averaging techniques, we show that strength can be measured from both speech and roars, and as predicted, strength is more reliably gauged from roars than vowels, words or greetings. The acoustic structure of roars explains 40–70% of the variance in actual strength within adults of either sex. However, strength is predicted by multiple acoustic parameters whose combinations vary by sex, sample and vocal type. Thus, while roars may maximally signal strength, more research is needed to uncover consistent and likely interacting acoustic correlates of strength in the human voice. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Early linguistic experience shapes bilingual adults’ hearing for phonemes in both languages

How do bilinguals represent category structure for phonemes in early acquired languages? /b/ and /p/ voice onset times (VOTs) are earlier and closer together in English than in Mandarin. Hence the category boundary and the steepness of the transition can show ‘tuning’ to language-specific acoustic structure (i.e., earlier boundary and steeper slope for English). As preregistered, we mapped identification functions of early English-Mandarin bilingual adults (N=66) on a /b/ - /p/ VOT continuum in each language. Individual bilingual-balance was derived using principal component analysis and entered into GLMMs of categorical boundary and slope. As predicted, VOTs were earlier for English than Mandarin. Early bilingual-balance predicted the slope of the transition between categories: Those who heard more English from an earlier age showed steeper slopes than those who heard more Mandarin. Findings are consistent with discrete representations for each language, and transfer of category structure from the earlier acquired language.

Frequent female song in blue tits: behavioural context suggests a role in intrasexual competition

The blue tit (Cyanistes caeruleus) is an important avian model in evolutionary ecology (> 20,000 published scientific studies). Song, like in other songbird species, is generally described as a male trait and plays an important role in mate attraction and territory defence. Over the decades, there have been recurring reports of anecdotal female song but these have not led to any quantitative study of female song in blue tits. Our systematic sampling over three years revealed prolific female singing in a northern population of colour ringed blue tits. Daytime singing of females occurred throughout the breeding season during agonistic interactions, solo songs and alarm situations, and these contexts are similar to male song. Notably, female song was absent during the dawn chorus; the period around sunrise when males sing intensively just before mating. Female and male song overlapped substantially in acoustic structure (i.e. same song types, peak frequency or trill rates) but there were also significant differences in that females had smaller repertoires, shorter trills and lower vocal consistency. Differential selections pressures related with contextual (functional) differences in the role of male and female song could explain the observed differences in acoustic structure. The new finding of prolific female singing in such a well-studied species suggests we ought to revise our understanding of male and female vocal communication in this (and probably other) species. Identifying the selection pressures associated to the convergence versus divergence of male and female song may provide important insight in understanding birdsong evolution.

Noise Reduction Effect of Porous Asphalt Pavement Based on Acoustic-Structure Coupling Model

Nowadays, the traffic noise problem is becoming increasingly prominent. In order to study the influence of porosity and pore depth on the noise reduction performance of asphalt pavement, this paper used the software COMSOL Multiphysics to establish acoustic-structure coupling models, and simulated the sound absorption and noise reduction effect of asphalt pavement under 10%, 15%, 20%, 25%, and 30% porosity; moreover, under the condition of unchanged asphalt pavement porosity, the sound absorption and noise reduction effect of asphalt pavement under 3cm, 4cm, 5cm, 6cm, and 7cm pore depth was studied as well. The research results reveal that, with the increase of porosity and pore depth, the sound absorption and noise reduction effect of asphalt pavement gets better.

Acoustic Structure Inverse Design and Optimization Using Deep Learning

From ancient to modern times, acoustic structures have been used to control the propagation of acoustic waves. However, the design of acoustic structures has remained a time-consuming and computational resource-consuming iterative process. In recent years, deep learning has attracted unprecedented attention for its ability to tackle hard problems with large datasets, achieving state-of-the-art results in various tasks. In this work, an acoustic structure design method is proposed based on deep learning. Taking the design of multiorder Helmholtz resonator as an example, we experimentally demonstrate the effectiveness of the proposed method. Our method is not only able to give a very accurate prediction of the geometry of acoustic structures with multiple strong-coupling parameters, but also capable of improving the performance of evolutionary approaches in optimization for a desired property. Compared with the conventional numerical methods, our method is more efficient, universal and automatic, and it has a wide range of potential applications, such as speech enhancement, sound absorption and insulation.

Introductory gestures before songbird vocal displays are shaped by learning and biological predispositions

Numerous animal displays begin with introductory gestures. For example, lizards start their head-bobbing displays with introductory push-ups, and many songbirds begin their vocal displays by repeating introductory notes (INs) before producing their learned song. Among songbirds, the acoustic structure and the number of INs produced before song vary considerably between individuals in a species. While similar variation in songs between individuals is a result of learning, whether variations in INs are also due to learning remains poorly understood. Here, using natural and experimental tutoring with male zebra finches, we show that mean IN number and IN acoustic structure are learned from a tutor. Interestingly, IN properties and how well INs were learned, were not correlated with the accuracy of song imitation and only weakly correlated with some features of songs that followed. Finally, birds artificially tutored with songs lacking INs still repeated vocalizations that resembled INs, before their songs, suggesting biological predispositions in IN production. These results demonstrate that INs, just like song elements, are shaped both by learning and biological predispositions. More generally, our results suggest mechanisms for generating variation in introductory gestures between individuals while still maintaining the species-specific structure of complex displays like birdsong.