Etude de la dispersion normale des caractéristiques auditives

Auditory performances were measured on two groups of normally-hearing listeners, for a total of 107 persons, whose ages ranged from 14 to 50 with a majority between 20 and 25. Aside from the classical audiogram, the variable tested were absolute and masked detection thresholds for one part, and discrimination thresholds for the rest. The main goal of this test battery was to get an estimate of the normal distribution of auditory capabilities for intensity, frequency, time and space variables ; but we also measured binaural fusion, stream segregation, timbre discrimination, and selectivity in general. The objective behind this investigation is to build a simplified model for auditory perception, based on a multidimensional representation. In this model, the main features of auditory perception could be represented by independant vectors, and each individual by his components relative to these vectors. A statistical analysis of our data show that it is not perfectly clear yet what the independant factors are. Nevertheless, a "psychoacoustic profile" can be defined, for each individual or for groups of individuals, based on a limited set of variables, that might prove to be a useful tool for some professional applications

Adaptation auditive et localisation

This paper presents the main results of an experiment on the possible role of adaptation in auditory localization. Measurements are performed in an anechoic room on the apparent azimuth of a brief 4-kHz tone, coming from the side (15°) of the listener, in the presence of a tone at the same frequency coming from the front. This frontal source is turned on first, for a certain amount of time, in order to induce some sort of auditory adaptation ; next, a 50-ms tone is presented from the lateral source. It is found that, as the duration of the pre-exposure is increased, the apparent azimuth of the second sound varies under some conditions ; in most cases, it is shifted towards the side of the subject, away from the actual position of the source. The same type of effect is demonstrated under earphones. In this case, the adapting signal is a diotic tone, and the adapted signal is a 50-ms dichotic tone with an interaural time difference of 70 µs. The summation of these tones leads to an interaural level difference, and therefore to a lateralized auditory image. The apparent location of this image also varies with adaptation, as in the first experiment

Auditory Evaluation of Sound Signals Radiated by a Vibrating Surface

International audienceThis paper presents a combination of vibroacoustic and psychoacoustic studies of sounds radiated by a vibrating structure. The calculated sound field is the sound pressure radiated by a baffled thin-plate structure immersed in a fluid, on the surface of which the acceleration is given. Various configurations are selected for the time and space functions of the acceleration variable, each configuration leading to a particular acoustic signal (a low-frequency tone complex in our case). These signals are then transformed into sound files, which are used as test signals in psychoacoustic experiments for assessing their perceptual attributes and quality. Two experiments were run. In the first one, the unpleasantness of a series of signals at different levels was measured by direct estimation and compared with their calculated loudness and sharpness using Zwicker's model. The same measurements were repeated with the signals set to the same maximum amplitude. In the second experiment, the pleasantness of another series of sounds at equal loudness was measured, as well as dissimilarity and preference on pairs of these sounds. An MDS analysis was run to extract auditory attributes that could account for the perceived differences between sounds and correlate with the estimated pleasantness. The results from the first experiment show that pleasantness is always highly (and negatively) correlated with loudness. The same holds for sharpness, when sounds are played at the same maximum amplitude. The second experiment shows that the perceptual attributes revealed by the MDS analysis are related to pitch and timbre, the latter being highly correlated with pleasantness. Overall, this study confirms the interest of extending vibroacoustic studies to a more complete "psychomechanical" investigation of the whole process of sound generation. It is suggested that such investigations may apply to product sound quality and to active or passive noise control, by providing psychoacoustic feedback to the design of the vibrating structures or of the noise-control systems

Récupération après adaptation induite de sonie

Scharf B., Botte M.-C., Canévet G. Récupération après adaptation induite de sonie. In: L'année psychologique. 1983 vol. 83, n°1. pp. 9-24

Investigating strain-induced crystallization through fatigue striations in filled NR

International audienceNatural Rubber (NR) exhibits a remarkable fatigue resistance, especially for non-relaxing loadings under which a strong lifetime reinforcement is observed (Cadwell et al. 1940). Such a resistance is classically attributed to strain-induced crystallization (SIC). At the microscopic scale, it has been shown that SIC induces striations on the fracture surface of NR samples tested under fatigue loadings (Le Cam and Toussaint 2010, Muñoz-Mejia 2011, Le Cam et al. 2013, Ruellan et al. 2018). In order to provide additional information on the role of SIC in the fatigue crack growth resistance of NR, striations are investigated through post-mortem analysis after fatigue experiments carried out under both relaxing and non-relaxing loadings. Results show that two striation regimes take place. Regime 1 corresponds to small striation patches with different orientations and Regime 2 induces zones with large and well-formed striations. As fatigue striations are observed for all the loading ratios applied, they are therefore not the signature of the reinforcement. Nevertheless, increasing the minimum value of the strain amplified the striation phenomenon and the occurrence of Regime 2. The analysis carried out unifies the results obtained in the literature for relaxing and fully relaxing loadings in the sense that increasing the loading, i.e. the tearing energy, leads to an increase in the crack growth rate Lindley (1973) and to a striation typology evolution, especially the striation size (Ruellan et al. 2018)

The relation between local structural distortion and the low-temperature magnetic anomaly in Fe_7S_8

ISSN:0953-8984ISSN:1361-648

Ubiquity of amplitude-modulated magnetic ordering in the H-T phase diagram of the frustrated non-Fermi-liquid YbAgGe

YbAgGe contains a magnetic geometrically frustrated kagome-like lattice that also features significant local single-ion anisotropy. The electronic state is established by hybridization of 4f and conduction electrons leading to heavy electronic masses. The competition between these various interactions leads to nontrivial behavior under external magnetic field, including a sequence of magnetic phase transitions, non-Fermi-liquid states, and possibly a quantum critical point. We present a series of neutron diffraction experiments performed in the mK temperature range and under magnetic fields up to 8 T in the hexagonal plane, revealing the microscopic nature of the first four subsequent magnetic states of this phase diagram. The magnetic phases are associated with the propagation vectors k(1) = (1/3 0 1/3) for H < 2 T, k(2) = (0 0 0.32) for 2 T < H < 3 T, k(1) = (1/3 0 1/3) for 3 T < H < 4.5 T, and k(3) = (0.195 0.195 0.38) for 4.5 T < H < 7 T. Our structural refinements reveal a strong modulation of the magnetic moment amplitude in all phases. We observe that the ordered moments of the three magnetically different Yb sites become increasingly different in field, which complies with the principle local anisotropy directions relative to the field direction. While the ordered moments are aligned predominantly in the hexagonal plane, we also find a significant out-of-plane component and a ferromagnetic contribution above 2 T. We discuss possible scenarios that may evolve around the phase boundary at 4.5 T, which is associated with putative quantum criticality as identified by various bulk probes. We propose further steps that are required to better understand the microscopic interactions in this material.This article is published as Larsen, C. B., E. Canévet, D. G. Mazzone, Ch Rüegg, B. Fåk, D. F. McMorrow, E. Ressouche et al. "Ubiquity of amplitude-modulated magnetic ordering in the H− T phase diagram of the frustrated non-Fermi-liquid YbAgGe." Physical Review B 104, no. 5 (2021): 054424. DOI: 10.1103/PhysRevB.104.054424. Copyright 2021 American Physical Society. Posted with permission. DOE Contract Number(s): AC02-07CH11358; 200020-182536; EP/N027671/1; EP/F032293/