Discrimination experiment of sound distance perception for a real source in near-field

International audienceThe ability of distance perception is quite important for our daily life. For the backward region where the vision cannot cover, listeners perceive objects only via binaural hearing, and the distance perception for a backward sound source is very important. It helps listeners to perceive an approaching sound source and avoid dangerous object especially when the sound source is in the rear. In the free field, the main acoustic distance perception cues for a nearby sound source include intensity variation with distance, binaural cues, dynamic cues, spectrum change and direct-to-reverberant energy ratio (Pavel Zahorik, 2005). Theoretically, all the above mentioned cues can be simulated via virtual auditory display (VAD), and realized by using a real sound source in an anechoic chamber. In comparison, the results based on a real sound source measurement should be more accurate. Previous researches have proved that the sound pressure has a giant influence on the ability of distance discrimination in both near field and far field when source is in front of head (Daniel H. Ashmead, 1990). However, few researches attempt to examine the binaural effect alone in distance perception. The theory was based on a fact that both the sound intensities and spectrums of a nearby sound will be different in two ears due to the head shadow, and these differences will change with distance when the sound source is lateral (PAUL D. COLEMAN, 1963). To verify the impact of binaural effect to distance discrimination, we conducted an experiment to exam the backward sound distance perception thresholds when the sound is presented from different azimuths in the horizontal plane. We used an automatic test system controlled by a computer in an anechoic room, eight listeners participated in the test. A loudness balanced band noise was used as test signals to remove the influence of sound level, and the signal was presented in 75 dBA. One signal was presented in the reference distance (50cm or 100cm), while the other one was presented in a closer distance, and sequence is random. The subjects need to do 2IFC (choose the closer one) between the signals presented in two different distances, and no feedback was given to subjects.The discrimination thresholds of two reference distances (0.5m and 1m) and five source azimuth (0°, 45°, 90°, 135°, 180°, right half plane of head) were examined in the experiment. The result show that subjects distance discrimination thresholds are lower when the sound source is on the side of head (about 20%) compared with front and back (above 30%), distinguishing two signals become quite difficult for participants when signals are presented in azimuth 0° and 180°. Moreover, this phenomenon is more prominent in 50cm compared with 100cm, while the effect of head shadow is more significant in 50cm. The results obtained in this study are consistent with previous studies and reveal that the binaural effect indeed contributes to distance discrimination process of human in a degree. This work is supported by the National Natural Science Foundation of China (Grant No. 11574090) and the Natural Science Foundation of Guangdong Province (Grant No. 2018B030311025)

Schottky-Contact Formation between Metal Electrodes and Molecularly Doped Disordered Organic Semiconductors

We study using three-dimensional kinetic Monte Carlo (KMC) simulations to what extent the formation of Schottky contacts between a metal electrode and a molecularly doped disordered organic semiconductor can be understood from the theory for crystalline inorganic semiconductors, adapted to include the effects of the localized nature of the states in which the charge carriers reside and the hopping transport in between these states. The thickness of the Schottky-contact depletion region is found to be significantly smaller than as expected when the energetical disorder is neglected. The presence of energetic disorder is also found to influence the voltage dependence of the width of the depletion regions near the contacts of single-layer double-Schottky-contact devices. The voltage drop over the two depletion regions and the remaining charge-neutral bulk layer is shown to be described successfully by a semianalytical model, based on an accurately parameterized bulk mobility function of the dopant concentration, energetic disorder, and the electric field. We furthermore find that the mobility in the depletion regions is drastically reduced. As a result, the depletion-region formation process can be ultraslow, with a characteristic time scale ranging from microseconds to beyond milliseconds.</p

Influence of Audiovisual Training on Horizontal Sound Localization and Its Related ERP Response

The objective was to investigate the influence of audiovisual training on horizontal sound localization and the underlying neurological mechanisms using a combination of psychoacoustic and electrophysiological (i.e., event-related potential, ERP) measurements on sound localization. Audiovisual stimuli were used in the training group, whilst the control group was trained using auditory stimuli only. Training sessions were undertaken once per day for three consecutive days. Sound localization accuracy was evaluated daily after training, using psychoacoustic tests. ERP responses were measured on the first and last day of tasks. Sound localization was significantly improved in the audiovisual training group when compared to the control group. Moreover, a significantly greater reduction in front-back confusion ratio for both trained and untrained angles was found between pre- and post-test in the audiovisual training group. ERP measurement showed a decrease in N1 amplitude and an increase in P2 amplitude in both groups. However, changes in late components were only found in the audiovisual training group, with an increase in P400 amplitude and decrease in N500 amplitude. These results suggest that the interactive effect of audiovisual localization training is likely to be mediated at a relatively late cognitive processing stage

Effect of Individualized Head-Related Transfer Functions on Distance Perception in Virtual Reproduction for a Nearby Sound Source

The head-related transfer function (HRTF) is dependent on the position of the sound source (both direction and distance) and is also affected by individual anatomical parameters. Individualized HRTFs have been shown to affect the perception of sound direction, but have not been considered in distance perception. This work aims to discover, by means of psychoacoustic experiments for a virtual reproduction system through a pair of in-ear headphones, the effect of individualized HRTF on auditory distance perception for a nearby sound source. The individualized HRTFs of six subjects and the non-individualized HRTFs of a mannequin at seven distances between 0.2 and 1.0 m and five lateral azimuths between 45° and 135° in the horizontal plane were processed with white noise to generate binaural signals. Further, the individualized and non-individualized HRTFs were used in the auditory distance perception experiments. Results of distance perception show that the variance of distance perception results among subjects is significant, the reason could be the stimuli are lack of dynamic cue and early reflections, or the audi tory difference of distance perception among subjects. However, via the analyses of mean slope of perceptual distance and correlation between the perceptual and real distance, we find that the individualized HRTF cue has insignificant influence on distance perception

Tribological analysis of oxide scales during cooling process of rolled microalloyed steel

The composition and phase transformation of oxide scale in cooling process (after hot rolling) of rolled microalloyed steels affect tribological features of rolled strip and downstream process, and the produced steel surface quality. In this study, physical simulation of surface roughness transfer during cooling process with consideration of ultra fast cooling (UFC) was carried out in Hille 100 experimental rolling mill, the obtained oxide scale was examined with SEM to show its surface and phase features. The results indicate that the surface roughness of the oxide scale increases as the final cooling (coiling) temperature increases, and the flow rate of the introduced air decreases. The cracking of the surface oxide scale can be improved when the cooling rate is 20 °C/s, the strip reduction is less than 12%, and the thickness of oxide scale is less than 15 μm, independent of the surface roughness. A cooling rate of more than 70 °C/s can increase the formation of retained wustite and primary magnetite precipitates other than the precipitation of α-iron. This study is helpful in optimising the cooling process after hot rolling of microalloyed steels to obtain quality surface products

Enhanced axial mixing of rotating drums with alternately arranged baffles

Traditional rotating drums are a popular type of tumbling mixer; however, they generally suffer from poor axial mixing with granular materials. To overcome this weakness, a system of alternately arranged baffles is presented, and its effect on particle mixing is numerically assessed using a GPU-based discrete element method. It is found that this arrangement of baffles displays better axial mixing performance than drums with (or without) traditional baffles, and that maximum mixing efficiency can be obtained through a suitable choice of baffle dimension and number. Essentially, this novel arrangement promotes the bulk movement of particles in the axial direction because of the combined radial scattering and axial guiding effects of the baffles. Together with the enhanced dispersive mixing, axial convective mixing serves to increase the axial mixing efficiency. Moreover, it is found that alternately arranged baffles produce good performance in various granular systems of rotating drums. Thus, the proposed system is a promising approach for industrial applications in more complicated mixers. (C) 2015 Elsevier B.V. All rights reserved

Extended Gersgorin Theorem-Based Parameter Feasible Domain to Prevent Harmonic Resonance in Power Grid

Harmonic resonance may cause abnormal operation and even damage of power facilities, further threatening normal and safe operation of power systems. For renewable energy generations, controlled loads and parallel reactive power compensating equipment, their operating statuses can vary frequently. Therefore, the parameters of equivalent fundamental and harmonic admittance/impedance of these components exist in uncertainty, which will change the elements and eigenvalues of harmonic network admittance matrix. Consequently, harmonic resonance in power grid is becoming increasingly more complex. Hence, intense research about prevention and suppression of harmonic resonance, particularly the parameter feasible domain (PFD) which can keep away from harmonic resonance, are needed. For rapid online evaluation of PFD, a novel method without time-consuming pointwise precise eigenvalue computations is proposed. By analyzing the singularity of harmonic network admittance matrix, the explicit sufficient condition that the matrix elements should meet to prevent harmonic resonance is derived by the extended Gersgorin theorem. Further, via the non-uniqueness of similar transformation matrix (STM), a strategy to determine the appropriate STM is proposed to minimize the conservation of the obtained PFD. Eventually, the availability and advantages in computation efficiency and conservation of the method, are demonstrated through four different scale benchmarks

ELAA Channel Characterization with Parameter Estimation Based on a Generalized Array Manifold Model

The extremely large antenna arrays (ELAAs) and millimeter-wave systems have become key techniques for obtaining higher frequency spectrum efficiency in sixth-generation (6G) communication systems. It is necessary to determine appropriate statistical models to describe the channel characteristics for the ELAAs, such as spatial non-stationarity, dispersion in angular domain, and spatial consistency. Thus, a signal model based on the generalized array manifold (GAM) that describes the dispersion in direction using the definition of the slightly distributed scatterer (SDS) is proposed in this work. An estimator for the parameters of the GAM model, namely GAM Space-Alternating Generalized Expectation-maximization (GAM-SAGE), is also designed. Moreover, a method to obtain a stochastic SDS-based channel model (SBCM) that is capable of reproducing the spatial consistency is proposed. The method is then used to establish measurement-based models for line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios using a 40×40 receiver (Rx) planar antenna array at a carrier frequency of 40 GHz. The results demonstrate that the SBCM is capable of achieving spatially consistent results and outperforms the specular-path (SP) models in completely characterizing the ELAA channels at millimeter-wave bands, which are fundamental for the design of 6G

Prog. Chem.

The mixing of granular materials is an important unit operation in many industries. Due to the complex behaviors of granular flows, general laws and fundamental mechanisms of granular flows in industrial mixers are not completely understood yet. As a detailed numerical approach, the discrete element method (DEM) describes the forces and motions of granular materials at the particle scale, and thus has notable advantages over experimental approaches in the research of mixing mechanisms. With the rapid developments of its models and the computational technologies, this method becomes more and more popular in the simulations of various mixing processes. The effects of particle properties, mixer types, and operating parameters on mixing rate and mixing mechanisms could be investigated comprehensively through DEM, which would be quite valuable for the design and optimization of mixers as well as their optimal operations. Moreover, the high computational cost of industrial-scale simulations could be greatly alleviated by the fast developments of computer hardware, such as the advent of graphics processing unit (GPU). This review summarizes the recent progresses of DEM simulations on mixing, with emphasis on the treatments for non-cohesive particles in different kinds of mixers (rotary and fixed), cohesive particles (fine and wet), non-spherical particles (direct description of shape and multi-sphere method), and large-scale implementations. Finally, future development of the DEM method in mixing simulations is prospected. The mixing of granular materials is an important unit operation in many industries. Due to the complex behaviors of granular flows, general laws and fundamental mechanisms of granular flows in industrial mixers are not completely understood yet. As a detailed numerical approach, the discrete element method (DEM) describes the forces and motions of granular materials at the particle scale, and thus has notable advantages over experimental approaches in the research of mixing mechanisms. With the rapid developments of its models and the computational technologies, this method becomes more and more popular in the simulations of various mixing processes. The effects of particle properties, mixer types, and operating parameters on mixing rate and mixing mechanisms could be investigated comprehensively through DEM, which would be quite valuable for the design and optimization of mixers as well as their optimal operations. Moreover, the high computational cost of industrial-scale simulations could be greatly alleviated by the fast developments of computer hardware, such as the advent of graphics processing unit (GPU). This review summarizes the recent progresses of DEM simulations on mixing, with emphasis on the treatments for non-cohesive particles in different kinds of mixers (rotary and fixed), cohesive particles (fine and wet), non-spherical particles (direct description of shape and multi-sphere method), and large-scale implementations. Finally, future development of the DEM method in mixing simulations is prospected.</p