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A MUSIC-ML (MML) processing algorithm for 3-dimensional localization of underwater acoustic sources using a 2-dimensional acoustic vector (AVS) array was proposed recently. The MML processor performs source localization with high accuracy and resolution. But the hardware and computational complexity of the MML processor is very high. In this paper we propose the use of compressive sampling of the...
In this paper, Argo data combined with altimetry data were used to investigate the effect of eddy on Sound Speed Profile (SSP) in Northwestern Pacific Ocean. A combination of the closed contours method and the Okubo-Weiss method is used to detect the eddy. Statistics of SSP anomalies induced by eddy have been calculated by removing the climatology from Argo profiles in eddy. Then effects of eddy on...
The Acoustic Vector Sensor can measure both pressure and particle velocity information of acoustic field at a point in space. By using the acoustic pressure and particle velocity information, a single AVS can get the unbiased estimation of target's bearing. But when the phase of each channel is inconsistent, the estimation precision will be badly affected. In order to solve this problem, this paper...
Drilled shaft is an important substructure foundation in building construction. A drilled shaft needs to be placed precisely in high accuracy and satisfy the diameter precision requirement. In order to measure the verticality and the diameter of a shaft, the M-superimposed Gaussian Echoes Model (GEM) is used to estimate the time of flight (TOF) of ultrasound. Compared to the conventional threshold...
The advent of ultrafast ultrasound imaging proved beneficial for capturing transient flow patterns which was never readily achievable before. Velocity estimation methods based on 2D block-matching outperform Doppler based methods by offering higher frame rate with the cost of increased uncertainty in presence of out-of-plane motion as a result of turbulent flow.
The Normalized Least-Mean Squares (NLMS) algorithm is a widely used method for linear system identification (e.g., for Acoustic Echo Cancellation (AEC), where the acoustic path between loudspeaker and microphone needs to be estimated). As soon as interferers or background noise are active, step size control becomes a crucial task in order to ensure a fast but stable adaptation. Conventional step size...
In the problem of acoustic source localization, time difference of arrival (TDOA) among multiple sensors is needed, which is often obtained through time delay estimation (TDE) techniques. Among the multiple TDE methods developed in the literature, the normalized multichannel frequency-domain least-mean-square (NMCFLMS) algorithm is shown robust to reverberation. The performance of this algorithm,...
Synthetic aperture systems rely on accurate knowledge of Transmitter (Tx) and Receiver (Rx) positions at each ping. In Synthetic Aperture Sonar (SAS), due to the nature of propagation and navigation in water, they have to be estimated by either physical sensors or raw data or a combination of these and employed to compensate motion errors. Hence, motion compensation is a major issue in SAS. In this...
Using delay in the time-of-flight (TOF) of an ultrasonic signal to estimate the lateral size of a scatterer was evaluated. A rolled steel sample featuring a 2 mm diameter side-drilled hole (SDH) was immersed in water. The maximum delay produced by the SDH was estimated from through transmission signals. To estimate SDH size the measured delay was compared to theoretical delays with straight path assumption...
Acoustic Vector Sensors (AVS) measure acoustic pressure as well as the acoustic particle velocity to estimate the acoustic intensity. The acoustic intensity, which is a vector quantity, represents the magnitude and direction of the active or propagating part of an acoustic field thus indicating the Direction of Arrival (DOA) of a received signal. This paper concerns with the feasibility of DOA estimation...
Human tissues are known to be viscoelastic (VE), a type of material described by two behaviors: dispersion and attenuation. Several methods have been developed to measure shear wave dispersion, but quantifying shear wave attenuation (α) has been less successful, particularly using amplitude-based methods. Shear wave displacement amplitudes are dependent on several factors including geometric spreading,...
This research quantitatively estimates stiffness by measuring the time-to-peak displacement directly along the acoustic radiation force (ARF) axis in contrast to shear wave elasticity imaging (SWEI) that measures shear wave velocity at lateral locations. We have shown previously in simulation results that an advanced displacement estimator reduces variability in the final stiffness estimate. Here,...
A Gaussian mixture model (GMM) is used in state-of-the-art i-Vector based speaker recognition systems for acoustic space division and prediction. The main purpose of such acoustic space clustering is to constrain the acoustic comparison in small regions where between-speaker differences are the main source of variability. In this study, we investigate two unsupervised discriminative approaches as...
In acoustic conditions with reverberation and coherent sources, various spatial filtering techniques, such as the linearly constrained minimum variance (LCMV) beamformer, require accurate estimates of the relative transfer functions (RTFs) between the sensors with respect to the desired speech source. However, the time-domain support of these RTFs may affect the estimation accuracy in several ways...
The presence of reflecting surfaces inside an enclosure is generally known to have an adverse effect in acoustic source localization and Direction of Arrival (DOA) estimation performance. In this paper, we focus on the problem of indoor multi-source DOA estimation along the horizontal plane, considering a circular sensor array which is placed just in front of one of the vertical walls of the room...
Based on the relationship between porosity (or lithological facies) and other petrophysical properties, Artificial neural networks (ANN) are respectively trained for porosity estimation and lithological facies classification, using core porosity (CPOR) data and core lithological facies interpretation results of part of core interval together with some well logs (petrophysical properties). After the...
Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder. Previous studies associated OSA with anatomical abnormalities of the upper respiratory tract that may be reflected in the acoustic characteristics of speech. We tested the hypothesis that the speech signal carries essential information that can assist in early assessment of OSA severity by estimating apnea-hypopnea index (AHI)...
Tissue characterization using quantitative ultrasound (QUS) parameters has received significant attention in recent years due to its potential to improve the detection and diagnosis of diseased states. However, the vast majority of studies in QUS tissue typing have used parameters derived from either longitudinal or shear waves in isolation, thereby discarding potentially useful complementary information...
The paper presents a method of echo azimuth angle estimation for ultrasonic range finders. The method is based on phase shift determination. Because of size of applied transducers it is not possible to determine the shift in a direct way. This problem is discussed and error analysis is presented as well as some experimental results.
This paper presents the implementation of a quantitative system of assessment by ultrasound, which allows the acoustic characterization of animal blood plasma, with potential applications in hematic biometric techniques. The system comprises a unidimensional electronic controller with step size 1 mm which enables the acoustic inspection of blood samples using an ultrasonic field incident with central...
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