Intensity Vector Research Articles

CRNN-Based Multiple DoA Estimation Using Acoustic Intensity Features for Ambisonics Recordings

Localizing audio sources is challenging in real reverberant environments, especially when several sources are active. We propose to use a neural network built from stacked convolutional and recurrent layers in order to estimate the directions of arrival of multiple sources from a first-order Ambisonics recording. It returns the directions of arrival over a discrete grid of a known number of sources. We propose to use features derived from the acoustic intensity vector as inputs. We analyze the behavior of the neural network by means of a visualization technique called layerwise relevance propagation. This analysis highlights which parts of the input signal are relevant in a given situation. We also conduct experiments to evaluate the performance of our system in various environments, from simulated rooms to real recordings, with one or two speech sources. The results show that the proposed features significantly improve performances with respect to raw Ambisonics inputs.

Influence of room modes on low-frequency transients: Theoretical modeling and numerical predictions

In the low-frequency range, a sound reproduction in enclosures is strongly influenced by excited room modes. While the spectral impact of acoustic modes on a room response is well recognized, there is no sufficient knowledge on how these modes affects transients. In the paper this issue has been examined theoretically and numerically for a room excited by a tone burst by using a modal expansion method supported by a computer implementation. To quantify a temporal accuracy of a sound reproduction, the new metrics referred to as the tone burst reproduction error was introduced. The basis for determining this quantity was a deviation between the tone burst amplitude and the amplitude of a sound pressure computed via the Hilbert transform. A numerical simulation was performed for an irregularly shaped enclosure having a form of two-room coupled system. Calculation results have proved that a high inaccuracy of a tone burst reproduction occurs at receiving points corresponding to sharp dips in a distribution of the steady-state sound pressure level. This is because in these points an amplitude of transient sound is much bigger than a tone burst amplitude. It was discovered that strong narrow peaks in the tone burst reproduction error are located at centers of vortices in the active sound intensity vector field. An influence of a sound damping in a room on a reproduction of a tone burst was also examined and it was found that a substantial increase in a wall sound absorption does not significantly improves a tone burst reproduction because it does not eliminate sharp dips in a distribution of the steady-state sound pressure level.

24-hour accelerometry in COPD: Exploring physical activity, sedentary behavior, sleep and clinical characteristics.

BackgroundThe constructs and interdependency of physical behaviors are not well described and the complexity of physical activity (PA) data analysis remains unexplored in COPD. This study examined the interrelationships of 24-hour physical behaviors and investigated their associations with participant characteristics for individuals with mild–moderate airflow obstruction and healthy control subjects.Patients and methodsVigorous PA (VPA), moderate-to-vigorous PA (MVPA), light PA (LPA), stationary time (ST), average movement intensity (vector magnitude counts per minute), and sleep duration for 109 individuals with COPD and 135 healthy controls were obtained by wrist-worn accelerometry. Principal components analysis (PCA) examined interrelationships of physical behaviors to identify distinct behavioral constructs. Using the PCA component loadings, linear regressions examined associations with participant (+, positive correlation; -, negative correlation), and were compared between COPD and healthy control groups.ResultsFor both groups PCA revealed ST, LPA, and average movement intensity as distinct behavioral constructs to MVPA and VPA, labeled “low-intensity movement” and “high-intensity movement,” respectively. Sleep was also found to be its own distinct behavioral construct. Results from linear regressions supported the identification of distinct behavioral constructs from PCA. In COPD, low-intensity movement was associated with limitations with mobility (−), daily activities (−), health status (+), and body mass index (BMI) (−) independent of high-intensity movement and sleep. High-intensity movement was associated with age (−) and self-care limitations (−) independent of low-intensity movement and sleep. Sleep was associated with gender (0= female, 1= male; [−]), lung function (−), and percentage body fat (+) independent of low-intensity and high-intensity movement.ConclusionDistinct behavioral constructs comprising the 24-hour day were identified as “low-intensity movement,” “high-intensity movement,” and “sleep” with each construct independently associated with different participant characteristics. Future research should determine whether modifying these behaviors improves health outcomes in COPD.

Spatial sound intensity vectors in spherical harmonic domain.

Sound intensity is a fundamental quantity describing acoustic wave fields and it contains both energy and directivity information. It is used in a variety of applications such as source localization, reproduction, and power measurement. Until now, intensity is defined at a point in space, however given sound propagates over space, knowing its spatial distribution could be more powerful. This paper formulates spatial sound intensity vectors in spherical harmonic domain such that the vectors contain energy and directivity information over continuous spatial regions. These representations are derived with finite sets of closed form coefficients enabling ease of implementation.

Self-healing properties of cosh-Airy beams

Analytical optical field of the cosh-Airy beam partially blocked by a finite opaque obstacle that has Gaussian absorption efficiency is derived. The distributions of the normalized intensity and Poynting vector for a cosh-Airy beam with and without an opaque obstacle are demonstrated in the observation planes. The effects of the obstacle size, the central coordinates of the opaque obstacle, the cosh parameter, the decay factor, and the transverse scale factor on the self-healing process and ability are analyzed, respectively. The meaningful case that the main lobe of the cosh-Airy beam is blocked partially by an obstacle is considered. In the process of beam propagation, the energy flow in the direction of the negative transverse axis converges into the center of the opaque obstacle, so as to reform the cosh-Airy beam. With the increase of the axial propagation distance, the convergence of the energy flow decreases and finally disappears. When the obstacle size is smaller, the self-healing process is faster, and the self-healing ability is higher. The more the central coordinates of the opaque obstacle deviate from the origin, the slower the self-healing process is, and the lower the self-healing ability is. For larger cosh parameter, the self-healing process is faster, and the self-healing ability is higher. The smaller the decay factor is, the faster the self-healing process is, and the higher the self-healing ability is. The smaller the transverse scale factor is, the faster the self-healing process is, and the lower the self-healing ability is. The self-healing ability of the cosh-Airy beam is higher than that of the corresponding Airy beam. The self-healing properties of cosh-Airy beams are robust.

Теоретические исследования многоэлектродного датчика составляющих вектора напряженности электрического поля в форме квадратной пластины из проводящего материала

Теоретические исследования многоэлектродного датчика составляющих вектора напряженности электрического поля в форме квадратной пластины из проводящего материала

Peculiarities of real shallow sea wave-guide vortex structure

The temporal vector-phase characteristics of the interference field of a low-frequency signal tone in a real wave-guide of shallow sea were taken under consideration. Physical objects were detected in the field of destructive interference, which, according to known features, are defined as local vortices of the intensity vector. "Static" vortices and vortices that perform periodic oscillatory motions in the direction along the axis of the wave-guide relative to the phase centre of the combined receiving device have been discovered. It has been demonstrated that the structure of vortices depends on signal/noise ratio. Signalling tone with a frequency of 88 ± 1 Hz from the near-surface moving sound source was taken under consideration. Introduced results of the full-scale experiment expand the concepts of real fundamental properties of the shallow sea acoustic field.

МЕТОДИКА ОЦЕНКИ ГОТОВНОСТИ К РАБОТЕ ОБОРУДОВАНИЯ АСПВБ ПЕРВОГО УРОВНЯ ИНФОРМИРОВАНИЯ НА ОБЪЕКТАХ ТЭК В ОСОБЫХ УСЛОВИЯХ

Introduction . The necessity of obtaining by decision makers (DM) of complete information on first level information distribution equipment operating readiness of Automated Process Control Systems (APCS) at any time. Data on the pre-fire condition at a facility of the fuel and energy complex (FEC) is transmitted using the control elements of Automated Fire and Explosion Safety Systems (AFES) as a part of the APCS. The connection of determining the state of readiness of the AFES equipment with the degree of preventive maintenance is shown. The aim of the study is to obtain a scientifically based tool for determining AFES equipment operating readiness. Research methods . In order to solve the problem, there was selected a six-level graph of strategic planning model that is offered to a DM for use while evaluating the first level information distribution AFES equipment operating readiness. The hierarchy is based on the implementation of plans for the maintenance, repair and replacement of equipment. There were simulated verification measures and remedial procedures by using the method of successive increments. Two problems of mathematical programming are proposed — linear and nonlinear one. In the first case, a new form of the objective function was obtained, taking into account the maximum efficiency of plans implementation. In the nonlinear formulation in different forms, the criterion search function is considered to estimate the maximum efficiency. Optimal task solving is a conclusion about the use of a certain resource for one specific event. Study results . The conclusion was made about the feasibility of using the entire resource for a specific event. When solving the optimization problem in the nonlinear formulation, the dynamism of the parameters of the planned work vector to bring the first level AFES information sources in the required state, as well as the work performance intensity vector, is noted. As a result, there was proposed an AFES equipment integral operating readiness formula for a certain number of remedial measures. Conclusion . A method for evaluating the effectiveness of remedial measures for AFES, taking into account the resource limited by special conditions, is obtained. The use of the method gives an opportunity for on-duty shifts of the fuel and energy complex facility to promptly respond to pre-fire situations.

Slow variations of the Earth’s magnetic field: technical, methodological and organizational features of measurements

Variations of the Earth’s magnetic field with times of several years or more reflect the processes within the planet and cause great scientific interest. Over the past 100 years the regular observations at magnetic observatories (MOs) and repeat stations are the only experimental basis for studying such variations. In recent decades, satellite measurements have complemented ground-based measurements, thus partially solving the problems of spatially highly heterogeneous global network of magnetic observatories. Absolute observations are made at MOs to get the total field intensity vector. Until now, these measurements are performed manually, they are labor intensity and subject to many factors, that are often poorly controlled and reduce the reliability of the results, especially over long periods of time (years and decades), including (1) systematic errors of used magnetometers; (2) magnetic pollution of the absolute pavilion and its surroundings (at a distance of the first hundred meters); (3) instability of the pillars and remote target required to determine magnetic declination; (4) changes of observers and their weak qualification. Significant methodological problems arise if MO is moved to new location without special activity or infrastructure of MO (pavilions or pillars) is changed without careful control. For long-term stability and reliability of measurements, magnetic observatories were joined in IAGA network and then INTERMAGNET. Within these networks, requirements and standards have been defined, absolute magnetometers are compared every two years and observers are being trained. Modern hardware technologies allow to solve partially problems the automation of absolute observations, the self-calibration of the magnetometers, the checking of the MO’s magnetic environment, etc. Fully automated measurement systems help to expand the MO network.

Crop Classification Based on Temporal Information Using Sentinel-1 SAR Time-Series Data

With the increasing temporal resolution of space-borne SAR, large amounts of intensity data are now available for continues land observations. Previous researches proved the effectiveness of multitemporal SAR in land classification, but the characterizations of temporal information were still inadequate. In this paper, we proposed a crop classification scheme, which made full use of multitemporal SAR backscattering responses. In this method, the temporal intensity models were established by the K-means clustering method. The intensity vectors were treated as input features, and the mean intensity vectors of cluster centers were regarded as the temporal models. The temporal models summarized the backscatter evolutions of crops and were utilized as the criterion for crop discrimination. The spectral similarity value (SSV) measure was introduced from hyperspectral image processing for temporal model matching. The unlabeled pixel was assigned to the class to which the temporal model with the highest similarity belonged. Two sets of Sentinel-1 SAR time-series data were used to illustrate the effectiveness of the proposed method. The comparison between SSV and other measures demonstrated the superiority of SSV in temporal model matching. Compared with the decision tree (DT) and naive Bayes (NB) classifiers, the proposed method achieved the best overall accuracies in both VH and VV bands. For most crops, it either obtained the best accuracies or achieved comparable accuracies to the best ones, which illustrated the effectiveness of the proposed method.

A Crop Classification Method Integrating GF-3 PolSAR and Sentinel-2A Optical Data in the Dongting Lake Basin.

With the increasing of satellite sensors, more available multi-source data can be used for large-scale high-precision crop classification. Both polarimetric synthetic aperture radar (PolSAR) and multi-spectral optical data have been widely used for classification. However, it is difficult to combine the covariance matrix of PolSAR data with the spectral bands of optical data. Using Hoekman’s method, this study solves the above problems by transforming the covariance matrix to an intensity vector that includes multiple intensity values on different polarization basis. In order to reduce the features redundancy, the principal component analysis (PCA) algorithm is adopted to select some useful polarimetric and optical features. In this study, the PolSAR data acquired by satellite Gaofen-3 (GF-3) on 19 July 2017 and the optical data acquired by Sentinel-2A on 17 July 2017 over the Dongting lake basin are selected for the validation experiment. The results show that the full feature integration method proposed in this study achieves an overall classification accuracy of 85.27%, higher than that of the single dataset method or some other feature integration modes.

Experimental investigation of a robust algorithm for unambiguous source directionalization by sharks

All fish can detect the three vector components of particle motion, enabling them to determine source bearing, but particle motion alone cannot resolve which direction is towards the source and which direction is away (i.e., there is a 180° ambiguity). However, fish with swim bladders can also detect acoustic pressure which enables such fish to resolve this 180° ambiguity. Proposed processing algorithms, though, often employ unrealistic restrictions such as sinusoidal time dependence and free-field conditions. We propose a robust algorithm for determining the unambiguous source direction by a fish that can detect acoustic pressure. The method is based on the time-averaged acoustic intensity vector (the time-integral of the product of pressure and particle velocity). This non-oscillatory quantity points in the direction of energy flow and hence directly away from the source. The algorithm has the advantage of being applicable to signals with any time dependence, in any propagation environment. For sharks, which do not have swim bladders, we hypothesize that the vertical component of particle acceleration can be substituted for pressure, provided that the shark is sufficiently close to the water surface. We test the validity of this hypothesis by determining the direction to the source for reef noise, a biologically relevant signal, and boat noise in a range-varying shallow water environment.

Laser optical measurement of acoustic phenomena in the near field of a supersonic jet using 2-D position sensitive detector

Acoustic measurement close to noise sources is significant to understand the generation mechanisms of jet noise. Microphones are generally used for the acoustic measurement, but they may disturb the flow and acoustic fields when they are used in the near field of a jet. In this study, an optical measurement method using a laser and 2-D position sensitive detector (PSD) is proposed for the acoustic measurement in the near field. In this method, 2-D PSD detects the angle and direction of the refraction of the laser path by acoustic wave passing, so that the propagating direction, as well as the acoustic intensity, is expected to be measured by this method. To discuss its validity, this method was applied to the acoustic measurement of a correctly expanded supersonic jet. In this experiment, microphone measurement was also carried out simultaneously, and cross correlation between the signals of these two measurements is discussed. Also, the measured spectra and propagating directions for different frequencies are compared with those of the acoustic intensity vector measurement.

Observations of resonances and antiresonances in modal propagation over muddy sediment layer

Measurements of signals generated over the New England mud patch, an area of ocean roughly 70 m deep characterized by a 10 m thick surficial mud-layer, by the Intensity Vector Autonomous Recorder (IVAR) are presented. IVAR is a bottom deployed system that measures both potential and kinetic energy roughly 1.2 m above the seafloor. Data originate from signals generated by a towed J15 source (transmission in the 50–500 Hz band), and signal underwater sound (SUS) MK-64 explosive sources, both part of the SCE17 signal set, and individual modes are identified by their unique Doppler shifts and/or through time-frequency analysis of dispersion. The density contrast between water and mud manifests a concentration kinetic energy in the water column, specifically when the water/mud interface intersects a node of the vertical mode functions. Following the work of Tolstoy (JASA 28(6), 1182–1192, 1956), data observations are fit to a representative sediment model through coupling two reduced waveguides, one representing the water column and the other the layered sediment, at their lattice points. The persistence of a resonance, which occurs at intersecting lattice points, is examined in terms of the range dependence in water depth and sediment structure.

Estimation of the source distance using the multiple three-dimensional acoustic intensimetry

A 3D acoustic intensimetry (AI) in tetrahedral configuration can be used for the source localization. Such a 3D AI module is compact, but it can also yield a precise bearing angle for the low Helmholtz numbers if some bias errors are compensated. In this study, besides the bearing angle, the source distance is estimated by using the multiple 3D AI probes with different acoustic centers. Because each AI module indicates a vector from the acoustic center to the source direction, the nearest point between any pair of line vectors can approximate the source position. The source position can be estimated by minimizing the least square error of the positions determined by multiple intensity vectors. Such idea is preliminarily tested with four 3D AI modules, of which each module is composed of 4 MEMS microphones separated by 30 mm. Four 3D AI modules are also arranged in a tetrahedron layout, and the source frequency range is 0.5–2 kHz. The distance between modules is varied for 150–250 mm range, and the source distance for 1–4 m range. Current test results reveal that the estimation error is less than about 2, 5, and 7% when the elevation angle is within 0–30°, 30–60°, 60–90°, respectively.

Localizing multiple targets with a single particle velocity sensor

The acoustic velocity sensor (AVS) measures the direction of a propagating plane wave by measuring instantaneously the particle velocity over a small volume in space. When multiple sound sources are present, the AVS no longer reports the correct directions as the sound intensity vectors (the product of pressure and velocity vector) get mixed up nonlinearly. A few methods have been proposed to extract the individual components from just one sensor by assuming, for example, spectral separability or nongaussianity. This paper shows it is in fact possible to extract the components without making such assumptions. The approach here is to constrain the signal with the acoustic impedance equation for multiple superposing plane waves and, applying various techniques, such as sparsity decomposition, to solve the derived least squares problem.

Underwater vector sensor communication in KOREX-17

The underwater acoustic communication channel is subject to multiple interactions with the ocean boundaries and refraction due to sound speed structure of water column, which produces significant time spread. This phenomenon is referred to as inter-symbol interference (ISI), which results in degradation of error performance. Recently, a time reversal technique has been used for reducing the ISI. However, this requires a large-size array with spatially separated receivers to obtain higher spatial diversity gain, and it becomes a limitation to its application in space-constrained environment. An acoustic vector sensor (combined pressure and particle velocity) can potentially yield a better communication performance relative to a system using only hydrophones. In this talk, communication data collected using a vector sensor known as IVAR (Intensity Vector Autonomous Receiver) during Korea Reverberation Experiment (KOREX-17) conducted in shallow water located at 34° 43′ N, 128° 39′ E on May 23–31, 2017. The characteristics of the channel as probed by a pressure-only versus combined pressure plus particle velocity system are discussed along with some performance results of a vector sensor communication system. [Work supported by the ADD(UD170022DD) and the National Research Foundation of Korea(NRF-2016R1D1A1B03930983).]

Vector intensity properties from direct and reverberant field from a mid-frequency sonar in shallow water

The Intensity Vector Autonomous Recorder (IVAR) is a benthic lander system that coherently measures 3-axis acoustic particle velocity and pressure (combined sensor). Results using IVAR in a mid-frequency propagation and reverberation study conducted near Geoje Island, Republic of Korea, are presented. The measurements were made within shallow semi-circular bay (depth ~25 m) with bay opening to deeper waters, and with directional wave measurements made within the bay waters. This presentation will focus on measurements made at a fixed range (100–1000 m, depending on test) from the Autonomous Reverberation Measurement System (ARMS), a benthic lander with a source and receive array mounted on a rotation stage in order to collect reverberation data as a function of bearing angle. Several vector and scaler metrics emerge based on different combinations of second-order acoustic fields are discussed, such as rate of energy transport and active and reactive intensity that lend insight into the process of shallow water reverberation. For example, in one continuous measurement made over a 12 hour period, there is high correlation between wave slope and horizontal beam width as determined with horizontal active intensity. This and other effects related to variability in shallow water reverberation will be discussed.

The rate of energy transport and direct measurements of group velocity

The Intensity Vector Autonomous Recorder (IVAR) is a bottom deployed system measuring both particle velocity and pressure (combined sensor). Results using IVAR in the Sediment Characterization Experiment (SCE17) conducted off New England (spring 2017), are presented. Data originate both from ship noise involving the closest point of approach (CPA) of a large transport vessel, and experimental SCE17 signals relating to Signal Underwater Sound (SUS) MK-64 explosive sources. Several vector and scaler metrics emerge based on different combinations of second-order acoustic fields; one is the rate of energy transport (U) to be emphasized here. For the CPA data, estimates of U versus frequency represent the speed of the net transport of acoustic energy [D’Spain et al., J. Acoust. Soc. Am. 89, 1991], and additional interpretations are presented. For the SUS data, arrivals from individual modes are resolved in time-frequency analysis. Vertical intensity is shown to be much less than horizontal, and estimates of U are identified with modal group velocity with some caveats to be discussed. For example, the group velocity associated with the Airy-phase for mode-2 (frequency ~29 Hz) is U ~ 1370 m/s. This estimate emerges directly from the analysis without recourse to range divided by travel time.

Enhancing the effectiveness of calculation of parameters for short circuit of three­phase transformers using field simulation methods

We conducted theoretical research into electromagnetic processes when testing power transformers under the mode of the test short circuit based on a three-dimensional model of the magnetic field in the frequency statement. Reliability and accuracy of determining the parameters for the test short circuit of the power transformer for frequency-domain statements were substantiated with the use of verification of the data of calculation of frequency-domain and time dependent models of the magnetic field for frequency statements. The main regularities of the magnetic field distribution in the volume of the active part of the transformer were determined. In the magnetic field localization zones, 3D intensity distribution is uniform and is determined by the 2D distribution in the horizontal cross section of the active part in the middle of the phase windings height. The values of the axial component of the magnetic field intensity approach 96–97 % of the intensity vector module. An effective approach to field modeling was implemented based on decomposition of the computational domain into spatial zones. Each calculation zone is put in compliance with an electrical circuit of the substitution scheme. Distribution of electric potentials in the horizontal cross-sections of the conductors between the coils or between the turns of windings was accepted as uniform. The superposition of magnetic fields in spatial zones was implemented by means of dynamic synthesis by the criteria of minimal current error for electric circuits of the substitution scheme. The decomposition of the 3D area of field simulation area into the central and end zones is implemented at a distance of 10–15 % of the height of the phase windings, which ensures high accuracy of the magnetic field calculation with the error not exceeding 1.62 %. Time consumption for field simulation of electromagnetic processes under the mode of the test short circuit decreased by 5 times and requirements for the capacity of computing hardware resources decreased by 4 times. High accuracy of identification of parameters of the test short circuit of three-phase transformers was proved by comparing the calculation data to the results of tests at the private company Eltiz (Zaporizhzhia, Ukraine). Calculation errors do not exceed 1.42 % for active losses and 1.39 % for short circuit voltage. The proposed approach with the use of the methods of decomposition and of dynamic synthesis makes it possible to significantly improve the effectiveness of the preliminary stage of design preparation of production and can be used for solving the problems of design solutions optimization