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Lung ultrasound imaging is a fast-evolving field of application for ultrasound technologies. However, most diagnoses are currently performed with imaging protocols that assume a quasi-homogeneous speed of sound in the volume of interest. When applied to the lung, due to the presence of air, this assumption is unrealistic. Consequently, diagnoses are often based on imaging artifacts and thus qualitative and subjective. In this paper, we present an image formation protocol that is capable of capturing the frequency dependence of well-known artifacts (B-lines) and visualizing it in real time, ultimately providing a quantitative assessment of the signals received from the lung. Previous in vitro studies have shown the potential of B-lines native-frequency for the characterization of bubbly medium, but this paper presents the first results on clinical data. The image formation process has been designed to work on lung tissue, and ultrasound images generated with four orthogonal bands centered at 3, 4, 5 and 6 MHz can be acquired and displayed in real time. Results show that B-lines can be characterized on the basis of their native frequency in vivo and open the way toward real-time quantitative lung ultrasound imaging. [ABSTRACT FROM AUTHOR]

Synthetic aperture sonar (SAS) provides high-resolution acoustic imaging by processing coherently the backscattered acoustic signal recorded over consecutive pings. Traditionally, object detection and classification tasks rely on high-resolution seafloor mapping achieved with widebeam, broadband SAS systems. However, aspect- or frequency-specific information is crucial for improving the performance of automatic target recognition algorithms. For example, low frequencies can be partly transmitted through objects or penetrate the seafloor providing information about internal structure and buried objects, while multiple views provide information about the object's shape and dimensions. Sub-band and limited-view processing, though, degrades the SAS resolution. In this paper, SAS imaging is formulated as an ℓ1-norm regularized least-squares optimization problem which improves the resolution by promoting a parsimonious representation of the data. The optimization problem is solved in a distributed and computationally efficient way with an algorithm based on the alternating direction method of multipliers. The resulting SAS image is the consensus outcome of collaborative filtering of the data from each ping. The potential of the proposed method for high-resolution, narrowband, and limited-aspect SAS imaging is demonstrated with simulated and experimental data. [ABSTRACT FROM AUTHOR]

This paper describes a vision-referential speech enhancement of an audio signal using mask information captured as visual data. Smartphones and tablet devices have become popular in recent years. Most of them not only have a microphone but also a camera. Although the frame rate of the camera in such devices is very low compared to the audio signal from the microphone, it will be useful to enhance the speech signal if both signals are used adequately. In the proposed method, the speaker broadcasts not only his/her speech signal through a loudspeaker but also its mask information through a display. The receiver can enhance the speech combining the speech signal captured by the microphone and the reference signal captured by the camera. Some experiments were conducted to evaluate the effectiveness of the proposed method compared to a typical sparse approach. It was confirmed that the speech could be enhanced even when there were different kinds of noise and a high level of real noise in the environments. Experiments were also conducted to check the sound quality of the proposed method. They were compared to clear audio data compressed with various bps mp3 format. The sound quality was sufficient for practical application. [ABSTRACT FROM AUTHOR]

The waveguide invariant in shallow water environments has been widely studied in the context of passive sonar. The invariant provides a relationship between the frequency content of a moving broadband source and the distance to the receiver, and this relationship is not strongly affected by small perturbations in environment parameters such as sound speed or bottom features. Recent experiments in shallow water suggest that a similar range-frequency structure manifested as striations in the spectrogram exists for active sonar, and this property has the potential to enhance the performance of target tracking algorithms. Nevertheless, field experiments with active sonar have not been conclusive on how the invariant is affected by the scattering kernel of the target and the sonar configuration (monostatic vs bistatic). The experimental work presented in this paper addresses those issues by showing the active invariance for known scatterers under controlled conditions of bathymetry, sound speed profile and high SNR. Quantification of the results is achieved by introducing an automatic image processing approach inspired on the Hough transform for extraction of the invariant from spectrograms. Normal mode simulations are shown to be in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis. [ABSTRACT FROM AUTHOR]

Understanding and compensating ultrasound attenuation losses is an important issue in photoacoustic imaging. To contribute to this effort, simulated attenuated time domain waveforms are compared to experimental waveforms. The experimental waveforms are acquired by transmitting broadband ultrasound pulses through distilled water and porcine fat tissue. Three well-known modeling approaches are examined in detail with regard to accuracy and computation time. Furthermore, the influence of attenuation on imaging resolution is addressed. In the present paper, the focus lies on the calculation of attenuated detector signals. The results, however, also provide clues about the quality of image reconstruction. [ABSTRACT FROM AUTHOR]

A method of acoustic imaging is discussed that potentially can improve the diagnostic capabilities of medical ultrasound. The method, given the name second order ultrasound field imaging, is achieved by the processing of the received signals from transmitted dual frequency band pulse complexes with at least partly overlapping high frequency (HF) and low frequency (LF) pulses. The transmitted HF pulses are used for image reconstruction whereas the transmitted LF pulses are used to manipulate the elastic properties of the medium observed by the HF imaging pulses. In the present paper, nonlinear propagation effects observed by a HF imaging pulse due to the presence of a LF manipulation pulse is discussed. When using dual frequency band transmit pulse complexes with a large separation in center frequency (e.g., 1:10), these nonlinear propagation effects are manifested as a nonlinear HF propagation delay and a HF pulse distortion different from conventional harmonic distortion. In addition, with different transmit foci for the HF and LF pulses, nonlinear aberration will occur. [ABSTRACT FROM AUTHOR]

The study of cavitation inception in liquids rarely yields reproducible data, unless special control is taken on the cleanliness of the experimental environment. In this paper, an experimental technique is demonstrated which allows repeatable measurements of cavitation activity in liquid-particle suspensions. In addition, the method is noninvasive: cavitation bubbles are generated using a shock-wave generator, and they are photographed using a digital camera. The cavitation activity is obtained after suitable image processing steps. From these measurements, the importance of the particle’s surface structure and its chemical composition is revealed, with polystyrene and polyamide particles generating the highest yields. Further findings are that cavitation nuclei become depleted with an increasing number of experiments, and the existence of nuclei with varying negative pressure thresholds. Finally, a decrease of the cavitation yield is achieved by prepressurization of the suspension—indicating that the cavitation nuclei are gaseous. [ABSTRACT FROM AUTHOR]

Detecting acoustic transients by signal-to-noise ratio (SNR) becomes problematic in nonstationary ambient noise environments characteristic of coral reefs. An alternate approach presented here uses signal directionality to automatically detect and localize transient impulsive sounds collected on underwater vector sensors spaced tens of meters apart. The procedure, which does not require precise time synchronization, first constructs time-frequency representations of both the squared acoustic pressure (spectrogram) and dominant directionality of the active intensity (azigram) on each sensor. Within each azigram, sets of time-frequency cells associated with transient energy arriving from a consistent azimuthal sector are identified. Binary image processing techniques then link sets that share similar duration and bandwidth between different sensors, after which the algorithm triangulates the source location. Unlike most passive acoustic detectors, the threshold criterion for this algorithm is bandwidth instead of pressure magnitude. Data collected from shallow coral reef environments demonstrate the algorithm's ability to detect SCUBA bubble plumes and consistent spatial distributions of somniferous fish activity. Analytical estimates and direct evaluations both yield false transient localization rates from 3% to 6% in a coral reef environment. The SNR distribution of localized pulses off Hawaii has a median of 7.7 dB and interquartile range of 7.1 dB. [ABSTRACT FROM AUTHOR]

Underwater ambient noise from the Beaufort Sea, collected in March 2016, is analyzed to investigate the effect that environmental changes in the region have on the spatial and temporal characteristics of the ice-generated ambient noise. In particular, the influx of warm Pacific water, so called the Beaufort Lens, has dramatically altered the level and vertical directionality of ambient noise, creating a low noise zone in the ∼75–250 m depth interval with a noise notch at low grazing angles. It is also demonstrated how the observed noise vertical directionality is consistent with ice-mechanical activity along an active pressure ridge ∼30–50 km from the recording array, as shown by satellite imagery. The discrete ranges to this ice activity explain the peak arrival angles between −10 to −15 degrees in noise vertical directionality, as well as the horizontal noise notch. Transient noise events associated with the ice activity are analyzed using an image processing approach with hierarchical clustering applied to the recorded spectrograms. The observed events are grouped into three categories—short-time-broadband, long-time-narrowband, and long-time-broadband—each likely generated through a different mechanism by the ice cover. The spectral and temporal distribution of these transients are discussed. [ABSTRACT FROM AUTHOR]

The need for automated methods to detect and extract marine mammal vocalizations from acoustic data has increased in the last few decades due to the increased availability of long-term recording systems. Automated dolphin whistle extraction represents a challenging problem due to the time-varying number of overlapping whistles present in, potentially, noisy recordings. Typical methods utilize image processing techniques or single target tracking, but often result in fragmentation of whistle contours and/or partial whistle detection. This study casts the problem into a more general statistical multi-target tracking framework and uses the probability hypothesis density filter as a practical approximation to the optimal Bayesian multi-target filter. In particular, a particle version, referred to as a sequential Monte Carlo probability hypothesis density (SMC-PHD) filter, is adapted for frequency tracking and specific models are developed for this application. Based on these models, two versions of the SMC-PHD filter are proposed and the performance of these versions is investigated on an extensive real-world dataset of dolphin acoustic recordings. The proposed filters are shown to be efficient tools for automated extraction of whistles, suitable for realtime implementation. [ABSTRACT FROM AUTHOR]

Due to the absence of Automatic Identification System data (used by 3.7% of the Calvi bay fleet), the acoustic monitoring of coastal environments presents difficulties. A specific visual monitoring protocol has been set up on a photographic observatory using the wide-angle camera GoPro®. The detection and localization of boats were carried by two image processing algorithms and allowed the creation of a map of maritime traffic for a surface of 3.48 km2. The ocean noise is described through two different scales (the individual scale and the global scale) which are linked to the traffic information. The Sound Pressure Level characterizes the individual sources and correlates with the distance of the nearest ship, whereas the Ambient Noise Level characterizes the background without individual sources and correlates with the number of boats present. A high spatial and seasonal variability due to coastal maritime traffic is observed in the broadband [100 Hz–30 kHz]. Closest to the traffic, the acoustic is punctuated by diel patterns of biological sounds and the use patterns of the boaters. In spite of an important diurnal flotilla (more than 550 boats per day), the nocturnal activity of fish remains an important element on the soundscape (average and median levels higher during the night). [ABSTRACT FROM AUTHOR]

Real-time magnetic resonance imaging (MRI) speech production data have expanded the understanding of vocal tract actions. This letter presents an Automatic Centroid Tracking tool, ACT, which obtains both spatial and temporal information characterizing multi-directional articulatory movement. ACT auto-segments an articulatory object composed of connected pixels in a real-time MRI video, by finding its intensity centroids over time and returns kinematic profiles including direction and magnitude information of the object. This letter discusses the utility of ACT, which outperforms other similar object tracking techniques, by demonstrating its successful online tracking of vertical larynx movement. ACT can be deployed generally for dynamic image processing and analysis. [ABSTRACT FROM AUTHOR]

In ultrasound imaging, an array of elements is used to image a medium. If part of the array is blocked by an obstacle, or if the array is made from several sub-arrays separated by a gap, grating lobes appear and the image is degraded. The grating lobes are caused by missing spatial frequencies, corresponding to the blocked or non-existing elements. However, in an active imaging system, where elements are used both for transmitting and receiving, the round trip signal is redundant: different pairs of transmit and receive elements carry similar information. It is shown here that, if the gaps are smaller than the active sub-apertures, this redundancy can be used to compensate for the missing signals and recover full resolution. Three algorithms are proposed: one is based on a synthetic aperture method, a second one uses dual-apodization beamforming, and the third one is a radio frequency (RF) data based deconvolution. The algorithms are evaluated on simulated and experimental data sets. An application could be imaging through ribs with a large aperture. [ABSTRACT FROM AUTHOR]

Annual salmon migrations vary significantly in annual return numbers from year to year. In order to determine when a species' sustainable return size has been met, a method for counting and sizing the spawning animals is required. This project implements a probability hypothesis density tracker on data from a dual frequency identification sonar to automate the process of counting and sizing the fish crossing an insonified area. Data processing on the sonar data creates intensity images from which possible fish locations can be extracted using image processing. These locations become the input to the tracker. The probability hypothesis density tracker then solves the multiple target tracking problem and creates fish tracks from which length information is calculated using image segmentation. The algorithm is tested on data from the 2010 salmon run on the Kenai river in Alaska and compares favorably with statistical models from sub-sampling and manual measurements. [ABSTRACT FROM AUTHOR]

Recently shock wave phenomena in living tissues are being widely applied in the fields of medical and chemical engineering, such as extracorporeal shock wave lithotripsy, bioprocess for environmental protection and tissue engineering. In the field of tissue engineering, the bone therapy to regenerate the bone by extracorporeal shock waves shows the possibility for new therapy. In this paper, to investigate the effects of shock waves on the endothelial cells in vitro, the cells by plane shock waves are observed by microscope and the growth rate and others are measured by image processing. The peak pressure works on the endothelial cells in water at the test case is 0.4 MPa. After working shock waves on suspended cells and fixed cells, the disintegration, shape and growth are investigated. It is found that the younger generation cells have small differences of shape index, and the growth rate of the shock-worked cells from 0 to 4 h are clearly high compared with control ones. It is concluded that once shock waves worked, some of them are disintegrated, but the other has capacity to increase growth rate of cell culture in vitro. [ABSTRACT FROM AUTHOR]

An automatic call recognition (ACR) process is described that uses image processing techniques on spectrogram images to detect and classify constant-frequency cricket and frog calls recorded amidst a background of evening sounds found in a lowland Costa Rican rainforest. This process involves using image blur filters along with thresholding filters to isolate likely calling events. Features of these events, notably the event’s central frequency, duration and bandwidth, along with the type of blur filter applied, are used with a Bayesian classifier to make identifications of the different calls. Of the 22 distinct sonotypes (calls presumed to be species-specific) recorded in the study site, 17 of them were recorded in high enough numbers to both train and test the classifier. The classifier approaches 100% true-positive accuracy for these 17 sonotypes, but also has a high false-negative rate (over 50% for 4 sonotypes). The very high true-positive accuracy of this process enables its use for monitoring singing crickets (and some frog species) in tropical forests. [ABSTRACT FROM AUTHOR]

Bats use echolocation to navigate three dimensional obstacles while locating, identifying, and engaging targets. A theory is offered of image processing during the search and navigation phase of echolocation that uses Doppler frequency shifts. The information in frequency changes across the angle of elevation can be used to generate a three dimensional model of the environment when combined with the timing and the relative amplitude of the returned signals. The mathematics of frequency shifts for an emitter traveling at a large fraction of the velocity of propagation (c) is presented. Reported behavior that can be explained by this phenomenon is discussed. [ABSTRACT FROM AUTHOR]