Regime change thresholds in flute-like instruments: influence of the mouth pressure dynamics

Since they correspond to a jump from a given note to another one, the mouth pressure thresholds leading to regime changes are particularly important quantities in flute-like instruments. In this paper, a comparison of such thresholds between an artificial mouth, an experienced flutist and a non player is provided. It highlights the ability of the experienced player to considerabily shift regime change thresholds, and thus to enlarge its control in terms of nuances and spectrum. Based on recent works on other wind instruments and on the theory of dynamic bifurcations, the hypothe- sis is tested experimentally and numerically that the dynamics of the blowing pressure influences regime change thresholds. The results highlight the strong influence of this parameter on thresholds, suggesting its wide use by experienced musicians. Starting from these observations and from an analysis of a physical model of flute-like instruments, involving numerical continuation methods and Floquet stability analysis, a phenomenological modelling of regime change is proposed and validated. It allows to predict the regime change thresholds in the dynamic case, in which time variations of the blowing pressure are taken into account

Using complementary visual approaches to investigate residency, site fidelity and movement patterns of the dusky grouper (Epinephelus marginatus) in a Mediterranean marine protected area

AbstractAssessing individuals' abundance, residency (presence at a site within a certain period) and site fidelity (tendency to return to the same site in subsequent seasons or years) is crucial for evaluating and improving the effectiveness of spatial conservation/management measures regarding ecologically and socio-economically valuable species. Using underwater visual census (UVC) and photo-identification (photo-ID) techniques, we estimated the abundance, residency and site fidelity of the dusky grouper, Epinephelus marginatus, at two protected sites within the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Italy) in the summers of 2017–2018. The scope and spatio-temporal resolution of the study was extended by involving volunteer recreational divers in the photo collection. Grouper mean densities varied significantly across sampling dates, with a significant variability between the 2 years and the two investigated sites. At least 94 grouper visited the study sites in the summers of 2017–2018 based on the analysis of 968 high-quality photos using a semi-automated software to photo-identify individuals. Overall, the most frequently sighted grouper was recorded on 32 different days and 21 individuals (22%) identified in 2017 were re-sighted in 2018. The participation of volunteer recreational divers helped detect the inter-site (3.5–4 km apart) movements of a female and a male, supporting previous findings regarding the occurrence of reproduction-related movements. This study provides novel insights into the residency and site-fidelity patterns of the dusky grouper, and its small-scale movements probably related to reproduction. Specifically, we provide indications that effective protection from fishing should encompass the entire area used by grouper for reproductive movements

Large plastic stability in magnesium alloys:crystalline vs. amorphous alloys

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Investigation of the influence of the torso, lips and vocal tract configuration on speech directivity using measurements from a custom head and torso simulator

The human voice is a directional sound source. This property has been explored for more than 200 years, mainly using measurements of human participants. Some efforts have been made to understand the anatomical parameters that influence speech directivity, e.g., the mouth opening, diffraction and reflections due to the head and torso, the lips and the vocal tract. However, these parameters have mostly been studied separately, without being integrated into a complete model or replica. The aim of this work was to study the combined influence of the torso, the lips and the vocal tract geometry on speech directivity. For this purpose, a simplified head and torso simulator was built; this simulator made it possible to vary these parameters independently. It consisted of two spheres representing the head and the torso into which vocal tract replicas with or without lips could be inserted. The directivity patterns were measured in an anechoic room with a turntable and a microphone that could be placed at different angular positions. Different effects such as torso diffraction and reflections, the correlation of the mouth dimensions with directionality, the higher-order modes and the increase in directionality due to the lips were confirmed and further documented. Interactions between the different parameters were found. It was observed that torso diffraction and reflections were enhanced by the presence of the lips, that they could be modified or masked by the effect of higher-order modes and that the lips tend to attenuate the effect of higher-order modes

Influence of speech sound spectrum on the computation of octave band directivity patterns

International audienceSpeech directivity induces variations of the amplitude and spectrum of the radiated sound with the direction. It is gaining interest for the rendering of speech in three dimensional environments (real or virtual), but it is also related to more fundamental research questions, such as the intelligibility with competing speech (cocktail party problem). Speech directivity is most often quantified by averaging in octave bands the speech production of real subjects recorded simultaneously at different locations with microphone arrays in anechoic environments. Due to the variability of the physical mechanisms of speech production, the radiation patterns differ between different speech sounds. However, a part of the observed variability may be due to the averaging process itself, which is influenced by the spectral differences between the different speech sounds. In order to investigate to what extent and in which frequency range this variability is actually due to differences in directionality, directivity patterns are computed in narrower frequency bands with constant width. The details revealed by this higher frequency resolution also allow one to identify the expected influence of the dimensions of the subjects, the mouth opening and the contribution of the nasal cavity to the sound radiation. Normalized octave band averages are computed and compared with the commonly performed octave band averages

Scale factor and punch shape effects on the expansion capacities of an aluminum alloy during deep-drawing operations

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Validation of an analytical compressed elastic tube model for acoustic wave propagation

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Influence of the punch geometry and sample size on the deep-drawing limits in expansion of an aluminum alloy.

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