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We analyzed the morphological characteristics of OCC (Ocean Core Complexes) in the middle part of the Central Indian Ridge (MCIR) using high-resolution geophysical data recorded on the Deep-Tow SideScan Sonar IMI-30 system. In terms of slope-gradient variations calculated from the high-resolution bathymetry data, the normal faults formed by seafloor spreading were associated generally with slopes > 30° and resulted in high backscatter intensities, which reflect more topographic effects than acoustic medium variation. However, the areas associated with gentle slopes < 10° tend to show the backscatter intensities reflecting the acoustic characteristic of the medium. We show that the detachment faults exposing the OCCs were initiated with high-angle normal faults (58°) exhibiting outward and inward dips of a breakaway zone. In order to examine the spatial distribution of OCC structures, we characterized the transition from magmatic-dominant seafloor with abyssal hills to tectonic-dominant seafloor with OCC using the down-slope direction variation. The slope direction of the seafloor generally tends to be perpendicular to the ridge azimuth in the magmatic-dominant zone, whereas it becomes parallel to the given ridge azimuth near the OCC structures. Therefore, this spatial change of seafloor slope directions indicates that the formation of OCC structures is causally associated with the tectonic-dominant spreading rather than magmatic extension. These results also suggest that the topographical characteristics of seafloor spreading and OCC structures can be distinguished using high-resolution geophysical data. Thus, we propose that the high-resolution bathymetry and backscatter intensity data can help select potential areas of exploitation of hydrothermal deposits in MCIR effectively. [ABSTRACT FROM AUTHOR]

• Acoustic vortex beam is introduced to ultrasound-mediated transdermal medication delivery. • A more efficient delivery is achieved with an acoustic vortex beam that exhibits a lower acoustic intensity. • Transversal acoustic radiation force can produce an improved permeability in addition to inertial cavitation. Ultrasound-mediated transdermal drug delivery exhibits various advantages such as biocompatibility, controllability and safety, which attracts plenty of interests within biomedical field. Current researches mostly emphasizes the acoustic cavitation generated by planar or focused waves while neglecting other physics that occur during transportation. Our experimental study illustrates the presence of an acoustic vortex (AV) beam that exhibits a lower acoustic intensity and typically means a lower dose of inertial cavitation, yet achieves a more efficient delivery. Such a result calls for the fundamental mechanism of ultrasound-mediated transdermal transfer using the AV beam. In this work, according to our knowledge, the AV beam is firstly introduced to ultrasound-mediated transdermal medication delivery. The transversal acoustic radiation force (T-ARF), which is the primary characteristic carried by the acoustic vortex beam, and its contribution to the transport enhancement are investigated. It is shown that a focused AV (FAV) beam with a maximal acoustic pressure of 200 kPa induces a pN-level T-ARF, which promotes the enlargement of pores on the stratum corneum and thereby enhances the permeability, as compared with a zero-order (non-vortex) counterpart. This contribution of the T-ARF is validated by the experimental transport on the cellulose membrane, which exhibits a significantly increased membrane porosity and delivery efficiency. The favorable results introduce the new degree of freedom into the ultrasound-mediated transdermal drug transport based on AV beam, and thereby promotes the development of a combined control strategy for more precise and efficient transdermal drug delivery in conjunction with the administration of acoustic cavitation. [ABSTRACT FROM AUTHOR]

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Low-Intensity Pulsed Ultrasound Stimulation (LIPUS) is a therapeutic modality used for bone tissue regeneration and healing. Its clinical efficacy is still debated, as the underlying physical phenomena remain poorly understood. The interaction between ultrasonic waves and cells, likely to trigger mechanotransduction inducing bone regeneration, is at the center of scientific concerns on the subject. In order to get new insights into these phenomena, the development of in vitro experiments is a key step but special attentions should be paid concerning to the actual acoustic area covered that has to be sufficiently large and homogeneous. To address this issue, an acoustic lens can be placed on the transducer to improve the homogeneity of the acoustic field over the entire cell culture area. A computational model is developed to test several shapes and heights of acoustic lenses and compare their effectiveness in order to find a compromise between the surface covered, the homogeneity of the intensity distribution and the acoustic pressure loss. All the lenses studied improve the enlargement of the field and its homogeneity but they all generate pressure acoustic loss. The best performing lens in terms of field homogeneity is the one that minimizes pressure acoustic loss but covers only 22% of the target surface. The best enlargement (68% of the surface covered) is obtained for a lens that produces a field that is 4 times less homogeneous and 3 times less efficient in terms of pressure acoustic loss. As no one lens is ideal, the choice of the lens should be the result of a compromise taking into account the prioritization of criteria. • Improvement of LIPUS in vitro tests. • Finite-Element model to develop an acoustic lens. • Acoustic lens to broaden and homogenize the acoustic field inside a Petri dish. • Acoustic lens attenuates the ultrasonic field. [ABSTRACT FROM AUTHOR]

Low-intensity ultrasound stimulation is a technique used in therapeutic ultrasound for bone regeneration. However, the underlying mechanisms are still poorly understood. In vitro studies on cell cultures are implemented to understand the processes involved. To analyze the effects of ultrasonic waves on cells, the control of the delivered acoustic intensity is essential. However, depending on the insonification protocol chosen, multiple reflections and standing waves that form inside the culture medium strongly hinder the estimates. In this work, we propose the development and the experimental validation of an anti-reflection cover. We demonstrate that this custom-designed device is effective in avoiding multiple reflections and makes it possible to artificially replace the layer of culture medium with a large amount of water. Finally, an analytical study of the acoustic intensity delivered to the cells is proposed.

There was a computational error in the reconstruction algorithm impacting the multi-source imaging, specifically regarding misclassification of some voxels when masking vertebral bone for spatial phase and amplitude corrections (SPC, SPAC, TDSPC) in Sec. The paragraph should now read: Canal localizations were considered successful if there was (1) >=40% mainlobe contour enveloping the ground truth in the presence of sidelobes >=20% I or i (2) >=20% mainlobe contours enveloping the ground truth without visible sidelobes, artifacts, or interference in the canal. Erratum: A numerical investigation of passive acoustic mapping for monitoring bubble-mediated focused ultrasound treatment of the spinal cord [J. Acoust. [Extracted from the article]

In the classic source–filter theory, the source of sound is flow modulation. "Flow" is the flow rate (Q) and flow modulation is dQ/dt. Other investigators have argued, using theoretical, computational, and mechanical models of the larynx, that there are additional sources of sound. To determine the acoustic role of dQ/dt in a tissue model, Q needs to be accurately measured within a few millimeters of the glottal exit; however, no direct measures of Q currently exist. The goal of this study is to obtain this waveform in an excised canine larynx model using time-resolved tomographic particle image velocimetry. The flow rate data are captured simultaneously with acoustic measurements to determine relations with vocal characteristics. The results show that glottal waveform characteristics such as maximum flow declination rate are proportional to the subglottal pressure, fundamental frequency, and acoustic intensity. These findings are important as they use direct measurements of the volume flow at the glottal exit to validate some of the assumptions used in the source–filter theory. In addition, future work will address the accuracy of indirect clinical measurement techniques, such as the Rothenberg mask. [ABSTRACT FROM AUTHOR]

Among the studies of musical instruments, one important, sometime underestimated discipline, is represented by ethnomusicology. The acoustic analyses on ethnic musical instruments (M.I.) are much more infrequent if compared to those on classical M.I. This article deals with the vibro-acoustic analysis on one of the most unknown ethnic, Italian M.I., i.e., the carabattola (also called battola), which used to be played in Italy until the late 1960s during the Holy Thursday before Easter. The study includes modal analysis and Intensity of Acoustic Radiation measured on an original carabattola, which was played in the Romagna area until the early twentieth century. After a brief overview about the theory of acoustic and vibrational analysis on musical instruments, the Intensity of acoustic radiation and its correlation with modal analysis are recalled, based on previous studies. In the experimental part of the article, the measurements conducted on the carabattola are described. Afterwards, the results obtained both from modal analysis and IAR measurements are analyzed and compared with other measurements previously conducted on musical (particularly percussion) instruments and commented. [ABSTRACT FROM AUTHOR]

The physics of musical instruments often uses modal analysis as one of the most important methods for describing the behavior of sound chests and their acoustic radiation. However, some studies conducted in Europe (Wogram), Japan (Suzuki) and the United States (Giordano) underlined a very weak correlation between sound radiation and modal analysis. This mismatch required further research. The acoustic parameter intensity of acoustic radiation (IAR) is highly related to the mechanical vibration of the sound source. IAR was able to quantify the sound efficiency of musical instruments, and to relate sound radiation with modal analysis. This paper investigates IAR measured on three Persian stringed musical Instruments, namely the thar, si-thar and santoor. The analysis contributes to the knowledge of stringed musical instruments and sound propagation, since IAR is capable of linking the mechanical vibrations of soundboards with the sound generation of the musical instruments. The IAR results coming from the modal analysis carried out during the study of the instruments are reported herein. [ABSTRACT FROM AUTHOR]

Measuring restoration outcomes is essential, but challenging and expensive, particularly on remote islands. Acoustic recording increases the scale of monitoring inexpensively; however, extracting biological information from large volumes of recordings remains challenging. Soundscape approaches, characterizing communities using acoustic indices, rapidly analyze large acoustic datasets and can be used to compare restoration sites against reference conditions. We tested this approach to measure nocturnal seabird recovery following invasive predator removal in the Aleutian Islands. We used recordings of nocturnal seabird soundscapes from six islands with varied histories of predators, from never invaded (one island) to 9–34 years post‐predator removal (four islands) and currently invaded (one island). We calculated 10 indices of acoustic intensity and complexity, and two pairwise indices of acoustic differences. Three indices reflected patterns of seabird recovery. Acoustic richness (measuring temporal entropy and amplitude) increased with time since predator removal and presence of historical predator refugia (r2 = 0.44). These factors and moonlight accounted for 30% of variation in cumulative spectral difference from the reference island. Over 10% of acoustic richness and temporal entropy was explained by Leach's Storm‐petrel (Oceanodroma leucorhoa) calls. However, indices characterized the soundscape of rat‐invaded Kiska Island like a never invaded island, likely due to high abiotic noise and few seabird calls. Soundscape indices have potential to monitor outcomes of seabird restoration quickly and cheaply, if confounding factors are considered and controlled in experimental design. We suggest soundscape indices become part of the expanding acoustic monitoring toolbox to cost‐effectively measure restoration outcomes at scale and in remote areas. [ABSTRACT FROM AUTHOR]

The characteristics of the reliable acoustic path (RAP) have been widely used to estimate source depth in the deep ocean. Here, a passive broadband source localization method that estimates both depth and range using the interference of the broadband signal with a non-synchronous vertical array in the RAP is demonstrated. The acoustic intensity distribution versus frequency and depth, which includes interference characteristics, is calculated from non-synchronous vertical array data and used to locate the source. Simulations and an experiment conducted in the western Pacific show that this method can successfully locate a broadband submerged source in the range of 10–30 km. [ABSTRACT FROM AUTHOR]

Based on the distribution of acoustic intensity at different depths at a fixed distance, a simple method is proposed to estimate the sound source depth at known range in the deep sea. First, the method calculates the acoustic intensity distribution of all the depths at a receiving distance. Second, the depths with the strongest acoustic intensity are selected. Sound sources are set at the selected depths to calculate the transmission loss (TL) at the same distance through the acoustic model, and the depth of the minimum superimposed TL is considered as the depth of the original sound source. The simulation and experiment verify the feasibility and reliability of the method. [ABSTRACT FROM AUTHOR]

Numerical simulation method based on Powell vortex sound theory is adopted to explore the mechanisms of acoustic field distribution characteristics of a centrifugal pump with different blade outlet angles. Results reveal that with the increasing of the angle, the fluctuation range of acoustic source at the tongue in time domain extends, which causes the same fluctuation characteristics of acoustic pressure. As the angle increases from 15° to 35°, the total acoustic source intensity (TASI) and total acoustic pressure level (TAPL) at the tongue increase by 1.68% and 2.54% on average under various rotational speeds, respectively. Additionally, the TASI and TAPL show the similar directivity characteristics under different angles, and the change of the angle has slight effect on the extremum distribution characteristics. Besides, the A-weighted average acoustic pressure level (L p) and A-weighted average acoustic source intensity level (L a) are adopted to describe the overall level of TAPL and TASI. When the angle increases from 15° to 35°, the L a and L p increase gradually and increase by 1.59% and 2.21% on average under various rotational speeds, respectively. The study reveals the acoustic source and acoustic pressure distribution characteristics in time and frequency domain qualitatively and quantitatively, and manifests that the distribution and variation patterns of acoustic source lead to those of acoustic pressure. The conclusions could lay a foundation for the empirical formula proposition between acoustic pressure and acoustic source. [ABSTRACT FROM AUTHOR]

Perfect sound absorption (PSA), producing an absorption coefficient of 1, can be achieved based upon the coherent interaction of acoustic waves, while it can merely be achieved within a narrow frequency-band due to critical impedance matching conditions. Here, we theoretically and experimentally study self-modulation and active-tunability in PSA created on account of a membrane-covered cavity. It is observed that due to the nonlinearity of the membrane, the frequency of PSA increases with the intensities of input acoustic waves, exhibiting a self-modulation property. Furthermore, we design an apparatus to control the elasticity of the membrane via four electromagnets, and thus, the PSA frequency can be freely and effectively adjusted by changing the direct-current driving voltage of the electromagnets. Despite the critical impedance matching conditions, the absorption coefficient achieved in our system holds at 1 when the PSA frequency is freely changed, which exhibits strong robustness in active-tunability. [ABSTRACT FROM AUTHOR]

The results of an experimental investigation of the discharge quenching by an acoustic wave are presented. Acoustic discharge quenching occurs as follows: an increase in the intensity of an acoustic wave causes a swirl, which mixes the gas in the radial direction, as a result of which the discharge in the tube shifts. An increase in the diameter of the positive column leads to an increase in the loss of charged particles on the walls of the tube, followed by an increase in the ionization frequency and the electric field. For a certain acoustic intensity, the voltage reaches a value that corresponds to the rated power of the supply unit, and at higher voltages the discharge is quenched. [ABSTRACT FROM AUTHOR]

• A semi-analytical model for power flow and structural intensity analysis of an ABH beam is established. • Arbitrary thickness variation profile is described as a general Fourier expansion. • Admissible function is constructed using an improved Fourier series with auxiliary terms. • Spatial and frequency characteristics of the ABH-specific energy transmission mechanism is revealed. A truthful description of the energy transport process is vital for the understanding of the Acoustic Black Hole (ABH) effect and its applications. One of the parameters, which can depict such a physical process is the power flow, whose calculation involves higher-order derivatives of the structural displacement function. This however requires an accurate and sufficiently smooth fitting of the structural responses which can hardly be achieved by the existing semi-analytical models on ABH structures. To tackle the problem, an energy formulation, in conjunction with a Rayleigh-Ritz procedure, is proposed for an ABH beam, whose thickness variation is described as a general Fourier expansion. The transverse displacement of the beam is constructed using Fourier series with supplementary auxiliary functions. This treatment ensures the continuity and the smoothness of all relevant derivatives terms in the entire calculation domain, thus allowing the calculation of the power flow and structural intensity. Numerical examples are presented to illustrate the reliability and the effectiveness of the established model. Numerical analyses on power flow and structural intensity show the spatial and frequency characteristics of the energy transmission process and reveal the ABH-specific mechanisms. While providing an efficient analysis tool, this work enriches the existing understanding on the dynamic behavior of ABH structures. [ABSTRACT FROM AUTHOR]

The span-wise obstacle on the suction surface of a hydrofoil has been verified to be an effective passive control method for cloud cavitation. The position of obstacle significantly influences the performance of cavitation control. In this research, we investigated the effect of obstacle position on attached cavitation control on the suction surface of a NACA0015 hydrofoil through response surface methodology. The cavitation types covered from sheet cavitation to partial and transitional cavity oscillations. We derived regression equations and built response surfaces to illustrate the quantitative relationship between individual factors (obstacle position, cavitation number, and angle of attack) and cavitation dynamic response parameters (cavity length, acoustic intensity, and energy flux). Sheet cavitation was effectively suppressed because the obstacle increased the pressure at the near-wall region. However, the obstacle would induce a shear cavitation when its position was too close to the leading edge of the hydrofoil. Under partial cavity oscillation conditions, the obstacle was consistently performed well in cloud cavitation control. The cavitation dynamic response parameters significantly decreased. Under transitional cavity oscillation conditions, the obstacle cannot suppress the cavitation because the transitional cavity oscillation was likely a system-inherent instability. This research is beneficial for a comprehensive understanding of cavitation control mechanism using an obstacle and for further industrial application of obstacle in hydraulic machinery to control cavitation. [ABSTRACT FROM AUTHOR]

A method is proposed for removing heat from the transducer of an acousto-optic deflector without substantial acoustic damping. The rear surface of the transducer and the heat–radiator surface are kept in contact through a thin sound-insulating fluid layer. The method is based on the considerable difference in the complex acoustic impedances for shear vibrations of fluids and a solid (the piezotransducer) by means of efficient heat transfer through the fluid. In the experiment, a continuous operation mode of the acousto-optic deflector is achieved with an acoustic wave intensity of more than 20 W/cm2. The acousto-optic deflector has been created that operates in the Bragg diffraction mode with a phase–modulation index of 3π with an input continuous controlling electric power of 3 W. The deflector characteristics for a light wavelength of 1.06 μm are as follows: diffraction efficiency no less than 90% in the 25 MHz frequency band at an absolute scanning angle of 40 mrad. [ABSTRACT FROM AUTHOR]

Focused acoustic vortex (FAV) beams can steadily trap particles in three-dimensions. Previous FAV emitters are mainly based on the active device arrays. Here, we design a passive artificial structure engraved with two sets of discrete Archimedean spiral slits to generate the FAV in water. The acoustic intensity and phase distributions of FAVs are investigated theoretically and demonstrated using the finite element method. The constructive interference between two transmitted acoustic vortices through the inner and outer spiral parts achieves the FAV. It is found that the focal length and depth of the FAV can be modulated by simply changing the initial radius of the Archimedean spiral. Furthermore, we implement the Schlieren imaging experiment to verify the generation of the FAV by the artificial structure. Our design may offer potential applications in particle trapping, biomedical therapy, and medical imaging. [ABSTRACT FROM AUTHOR]

Highlights • Effect of droplet banding on demulsification process is analyzed. • Optimal acoustic intensity and treatment time are obtained. • Acoustic cavitation threshold in emulsions is achieved by spectral analysis. • Range of oil-water properties suitable for ultrasonic separation is determined. Abstract This paper focuses on the application range and optimal parameters for separating water-in-oil (W/O) emulsions using ultrasonic standing waves (USWs). Firstly, the effect of droplet bandings on the demulsification process is theoretically analyzed. The formation of droplet bandings coincides with droplet sedimentation when horizontal irradiation is applied, which improves the separation efficiency. On this basis, the effects of acoustic parameters and oil-water properties on demulsification are analyzed in detail. It is shown that ultrasonic treatment is an efficient demulsification method, and that maximum demulsification efficiency can be achieved by optimizing the acoustic intensity and treatment time. Excessive acoustic intensity causes acoustic cavitation in low-frequency USWs and acoustic streaming in high-frequency USWs, resulting in a low separation efficiency. Acoustic cavitation also causes secondary emulsification, dispersing tiny oil droplets into separated water. In addition, ultrasonic separation is significantly affected by oil-water properties. The demulsification efficiency of W/O emulsions decreases with increasing oil viscosity and decreasing oil-water interfacial tension. Ultrasonic treatment has significant advantages for separation of emulsions with low water content and interfacial tension. This study presents an in-depth analysis of ultrasonic separation. [ABSTRACT FROM AUTHOR]

Objective: High intensity focused ultrasound (HIFU) treatment in the abdominal cavity is challenging due to the respiratory motion. In the self-scanning HIFU ablation method, the focal spot is kept static and the heating pattern is obtained through natural tissue motion. This paper describes a novel approach for modulating the HIFU power during self-scanning in order to compensate for the effect of tissue motion on thermal buildup. Methods: The therapy, using hybrid ultrasound (US)/magnetic resonance (MR) imaging, consists of detecting and tracking speckle on US images in order to predict the next tissue position, and modulating the HIFU power according to the tissue speed in order to obtain a rectilinear pattern of uniform temperature elevation. Experiments were conducted on ex vivo tissue subjected to a breathing-like motion generated by an MR-compatible robot and sonicated by a phased array HIFU transducer. Results: US and MR data were free from interferences. For both periodic and non-periodic motion, MR temperature maps showed a substantial improvement in the uniformity of the temperature elevation by using acoustic power modulation. Conclusion: The presented method does not require a learning stage and enables a duty cycle close to 100%, higher average acoustic intensity and avoidance of side lobe effects versus performing HIFU beam steering to compensate tissue motion. Significance: To our knowledge, the proposed method provides the first experimental validation of the self-scanning HIFU ablation paradigm via a real-time hybrid MRI/US imaging, opening the path toward self-scanning in vivo therapies. [ABSTRACT FROM AUTHOR]

Abstract The three-dimensional (3D) acoustic intensity probe is not popularly used for the source localization of acoustic source because of the large error even though the technique has been well known. In particular, the measured direction-of-arrival strongly depends on the frequency, which is a detrimental drawback that hampers the use of this method. Such spectral bias error, due to the discrete positioning and spacing of sensors surrounding the acoustic center, fluctuates in a nearly regular spectral pattern when a 3D acoustic intensity probe configured in a tetrahedral shape is used. In this work, two error compensation methods are tried: The first method is to adopt a double-module configuration, which is formed by the connected assembly of two intensity modules, but with different locations of acoustic centers for a spatial averaging effect. The second one is the 1/3-octave band averaging of the measured intensity spectrum within the effective measurement range. Because two probe modules are attached, they concatenate 1–3 sensors in the overlap position. Four double-module probes different in assembly configuration of involved two single-modules are tested: modules having a same acoustic center but twisted by 60°, inverted modules sharing one microphone and twisted by 60°, symmetric modules having the joint angle of 60° in the sharing edge, symmetric modules to a common face thus sharing three microphones. Measurements are conducted in an anechoic chamber by changing the source positions for 4 azimuth and 3 elevation angles. The results reveal that the maximum mean bias error of about 4° can be obtained by the double-module 3D acoustic intensity method, depending on the module configuration and angular source position. This contrasts to the fluctuating direction-of-arrival within about ±10° error range, which is obtained by each single-module in a concatenated double-module. In particular, when the band averaging technique is applied to the measured data by the probe module composed of the inverted single modules, the maximum bias error can be reduced to less than 1° in both azimuth and elevation angles. [ABSTRACT FROM AUTHOR]

This paper explores the change of the concept of a tritone – from its prohibition to tritonic apotheosis as well as draws attention to the acoustic peculiarities of the „Devil's interval” (Diabolus in musica1). The tritone is a very small object but features a portentous and unique sound as well as problematic intensity. The peculiarity of the discussed interval has evoked multifarious creative expressions and has also provoked controversial theoretical speculations throughout the music history. This paper aims to draw a historical perspective providing a comprehensive representation of both theoretical and practical approach to the tritone in relation to its acoustic intensity and rhetorical aspects. Critical consideration of the most remarkable theoretical declarations as well as analytical inquiry of particular musical examples reveal the significance and functionality of a tritone in different historical contexts. The paper reveals the constant change of conceptions, canons of usage, composition techniques and harmonic systems although referring to the same object on discourse. [ABSTRACT FROM AUTHOR]

Ultrasonically actuated microbubble oscillations hold great promise for minimally invasive therapeutic interventions. However for their successful translation to the clinic, real-time methods to control the amplitude and type of micro-bubble oscillations (stable versus inertial acoustic cavitation) and ensure that cavitation occurs within the targeted region are needed. In this paper, we propose a real-time nonlinear state controller that uses specific frequency bands of the microbubble acoustic emissions (harmonic, ultra-harmonic, etc.) to control cavitation activity (observer states). To attain both spatial and temporal controls of cavitation activity with high signal-to-noise ratio (SNR), we implement a controller using fast frequency-selective passive acoustic mapping (PAM) based on the angular spectrum approach. The controller includes safety states based on the recorded broadband signal level and is able to reduce the sensing inaccuracy with the inclusion of multiple frequency bands. In its simplest implementation, the controller uses the peak intensity of the passive acoustic maps, reconstructed using the third harmonic (4.896 ± 0.019 MHz) of the excitation frequency. Our results show that the proposed real-time nonlinear state controller-based PAM is able to reach the targeted level of observer state (harmonic emissions) in less than 6 s and remain within 10% of tolerance for the duration of the experiment (45 s). Similar response was observed using the acoustic emissions from single element passive cavitation detection, albeit with higher susceptibility to background noise and lack of spatial information. Importantly, the proposed PAM-based controller was able to control cavitation activity with spatial selectivity when cavitation existed simultaneously in multiple regions. The robustness of the controller is demonstrated using a range of controller parameters, multiple observer states concurrently (harmonic, ultra-harmonic, and broadband), noise levels (–6 to 12 dB SNR), and bubble concentrations (0.3–180 × 103 bubbles per microliter). Under preclinical and clinical conditions, more research in this direction is warranted. [ABSTRACT FROM AUTHOR]

The studies reported here addressed analysis of the N1 and P2 components and mismatch negativity (MMN) on discrimination of signals with dynamic changes in intensity in different acoustic contexts. Changes in context in the conditions of the oddball paradigm were created on the basis that each stimulus operated both as a standard and as a deviant in different series, such that the physical differences between signals remained unaltered and their functional relationship flipped to the opposite. Three types of sound signal were used: stimuli with constant intensity and two amplitude-modulated stimuli (linear and stepwise, each with an increase or decrease in intensity). Increases and decreases in the intensity of deviant stimuli induced MMN in the late latency period (>250 msec) without overlap with the N1 component. The difference in signals with linear and stepwise amplitude modulation indexed by mismatch negativity was determined by the direction of deviation in the structure of the sound series. Increment MMN anticipated decrement MMN by 90–100 msec regardless of the type of modulation. Amplitude differences were seen in responses to deviants with stepwise modulation in the context of consistent standards: increment MMN was greater than decrement MMN. The acoustic context affected only increment MMN. These results are consistent with views of the asymmetry in the perception of increasing and decreasing sound intensity, associated with their different biological significance. [ABSTRACT FROM AUTHOR]

Understanding the effect of the liquid depth (z) on the acoustic generation of hydrogen is highly required for designing large-scale sonoreactors for hydrogen production because acoustic cavitation is the central event that initiates sonochemical reactions. In this paper, we present a computational analysis of the liquid-depth effect on the generation of H2 from a reactive acoustic bubble trapped in water irradiated with an attenuating sinusoidal ultrasound wave. The computations were made for different operating conditions of frequency (355–1000 kHz), acoustic intensity (1–5 W/cm2), and liquid temperature (10–30°C). The contribution of the acoustic wave attenuation on the overall effect of depth was appreciated for the different conditions. It was found that the acoustic generation of hydrogen diminished hardly with increasing depth up to z = 8 m, and the depth effect was strongly operating parameter-dependent. The sound wave attenuation played a crucial role in quenching H2 yield, particularly at higher z. The reduction of the H2 yield with depth was more pronounced at higher frequency (1000 kHz) and lower temperature (10°C) and acoustic intensity (1 W/cm2). The attenuation of the sound wave may contribute up to 100% in the overall reductive effect of depth toward H2 production rate. This parameter could be imperatively included when studying all aspects of underwater acoustic cavitation. [ABSTRACT FROM AUTHOR]

In this work, numerical methods to identify the surface areas of a vibrating structure that radiate sound are implemented for cases of structures with inhomogeneous distributions of viscous Rayleigh damping. The intensity-based techniques correspond to acoustic intensity evaluated in terms of the acoustic pressure and particle velocity, non-negative intensity evaluated in terms of the acoustic impedance matrix obtained at the structural surface, and back-calculated non-negative intensity evaluated in terms of the acoustic impedance matrix obtained at a far-field receiver surface. Different configurations of inhomogeneous damping are applied to two elastic structures corresponding to a plate and a cylindrical shell. To examine the influence of inhomogeneous damping on sound radiation, the acoustic intensity on the structural surface, the acoustic intensity on several different far-field receiver surfaces, non-negative intensity and back-calculated non-negative intensity are numerically compared for different inhomogeneous damping cases. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Performance analysis of arrays of acoustic vector sensors (AVSs) for underwater surveillance. • Frame hosting the AVSs is not acoustically transparent introducing phase/gain mismatch of signals. • Coherent processing of acoustic intensities at each AVS with adaptive equalization of distortions. • Analysis of real data collected at sea with a bottom node with 2 AVSs and a towed array of 5 AVSs. • Comparison with Cramer-Rao Lower Bound of DOA estimation (the method is asymptotically efficient). This paper introduces a method to coherently combine the signals collected by the directional and omnidirectional channels of an Acoustic Vector Sensor array when the supporting frame is introducing a phase and gain mismatch error. The proposed method adaptively estimates the distortion introduced by the supporting frame and corrects the measurements at the sensors before their coherent combination. The paper evaluates the Cramer-Rao Lower Bound for Direction of Arrival estimation and compares the bound with simulated data and real data collected at sea. The proposed method is asymptotically efficient, reaching the lower bound for sufficiently large values of the signal to noise ratio. [ABSTRACT FROM AUTHOR]

A recent publication by Duan et al. [J. Acoust. Soc. Am. 142(3), EL245–EL250 (2017)] analyzed the interference pattern observed in the plot of acoustic intensity versus source-receiver range and frequency in deep water. This paper extends this work by applying an equivalent acoustic intensity surface versus the vertical angle of arrivals and frequency to depth estimation of broadband sources. A matched-interference-structure (MIS) method that processes the whole acoustic intensity surface is proposed and formulated as a filtration of the surface where the binominal filter weights ±1 for each surface grid point and presumed source depth are based on model-based interference structures. For comparison, the conventional method of matching multipath delays is reformulated and applied to process the surface. Because the numerical prediction of interference structures can be costly, analytical expressions are derived to improve the efficiency. Monte Carlo simulations are carried out to compare the performance and experimental data of broadband random sequences and pulse sources are used to illustrate the methods. The MIS method has a higher resolution and can work under a lower signal-to-noise ratio in the case of weak source depth fluctuation but is not as robust to the large source depth fluctuation as the other method. [ABSTRACT FROM AUTHOR]

In the ocean environment, the minimum variance distortionless response beamformer usually has the problem of signal self-cancellation, that is, the acoustic signal of interest is erroneously suppressed as interference. By exploring the useful information behind the signal self-cancellation phenomenon, a high-precision direction estimation method for underwater acoustic sources is proposed. First, a pseudo spatial power spectrum is obtained by performing unit circle mapping on the beam response in the direction interval. Second, the online calculation process is given for reducing the computational complexity. The computer simulation results show that the proposed algorithm can obtain satisfactory direction estimation accuracy under the conditions of low intensity of acoustic source, strong interference and noise, and less array snapshot data. [ABSTRACT FROM AUTHOR]

Abstract An effective technique for fine particle removal using the combined effect of acoustic field and seed nuclei was presented. The key operation parameters, such as sound pressure level, initial particle number concentration, seed nuclei and particle properties on the agglomeration and capture performance of fine particles were investigated experimentally. The results showed that the separation of fine particle was improved efficiently with the combined external fields. Fine particle removal efficiencies increased by 25% with the combined effect of acoustic field and droplets at a SPL of 153 dB. Removal efficiency increased with the seed nuclei size. The value increased from 20% to 50% as the seed particle size increased from 10 to 30 μm, but removal efficiency showed few changes when seed particle size was larger than 30 μm. Particle removal efficiency correlated well with the initial particle number concentration in the combined effect fields. The removal efficiency with the combined effect of acoustic field and droplets was much higher than those with the combined effect of acoustic field and solid seed particles in high particle loading. Fine particle removal was significantly impacted by the particle wettability, when the combined effect of acoustic field and droplets was used. The removal efficiency of MWI particles was improved by 20% with the combined effect of acoustic field and droplets, comparing to the removal efficiency of BC particles. Fine particle removal efficiency can be highly improved with the combined external fields, especially in low acoustic intensity. Graphical abstract Unlabelled Image Highlights • Interaction of fine particles and seed nuclei with acoustic activity was presented. • The agglomeration properties of fine particles are changed by different seed nuclei. • Fine particle removal efficiency is highly improved with AFSD for good wettability particles. • Removal efficiency with AFSD is much higher than the value with AFSP in high particle loading. • Combined effects contribute to improve fine particle removal efficiency in low acoustic intensity. [ABSTRACT FROM AUTHOR]

Acoustic cavitation concentrates and releases a very large amount of energy in localized areas, which can be used for many physical and chemical processes. Even though acoustic cavitation has been studied widely for decades in lab-scale sonoreactors, only few studies have been devoted to characterize this event in big-scale sonoreactors, where the liquid depth may have a critical influence on the bubble collapse. The present computational study furnished numerical data about the effect of depth ( z  = 0–10 m) on acoustic cavitation with special focus on the role of attenuation of the ultrasound wave on the dramatic conditions developed within bubbles at collapse. The used mathematical model takes into account the liquid compressibility, surface tension and viscosity, depth as well as the attenuation of the ultrasound wave with depth. It was found that the maximum bubble temperature (T max ) and pressure ( p max ) at the collapse diminished considerably with deepening into water up to 10 m with a considerable contribution of the ultrasound wave attenuation in the overall reduction event. The reduction in T max and p max with depth was more pronounced at higher frequency (1000 kHz) and lower temperature (10 °C) in which losses of about up to 72% in T max and till 94% in p max (as compared with values at z  = 0) were obtained at z  = 10 m. Depending on operating conditions, i.e. frequency, acoustic intensity or liquid temperature, the ultrasound wave attenuation may contribute with up to 47% and 79% in the overall reductive effect of depth toward T max and p max , respectively. These results were discussed, interpreted and used to support some available experimental observations. Finally, the results of the present study may help in designing large-scale sonoreactors through providing data about the effect of one of the missing links between lab-scale sonoreactors and industrial large-scale sonoreactors. [ABSTRACT FROM AUTHOR]

Yes-associated protein (YAP) acts as a mechanotransducer in determining the cell fate of murine C2C12 mesenchymal precursors as investigated after stimulation with ultrasound. We applied Focused Low-Intensity Pulsed Ultrasound (FLIPUS) at a sound frequency of 3.6 MHz, 100 Hz pulse repetition frequency (PRF), 27.8% duty cycle (DC), and 44.5 mW/cm2 acoustic intensity ISATA for 5 minutes and evaluated early cellular responses. FLIPUS decreased the level of phosphorylated YAP on Serine 127, leading to higher levels of active YAP in the nucleus. This in turn enhanced the expression of YAP-target genes associated with actin nucleation and stabilization, cytokinesis, and cell cycle progression. FLIPUS enhanced proliferation of C2C12 cells, whereas silencing of YAP expression abolished the beneficial effects of ultrasound. The expression of the transcription factor MyoD, defining cellular myogenic differentiation, was inhibited by mechanical stimulation. This study shows that ultrasound exposure regulates YAP functioning, which in turn improves the cell proliferative potential, critical for tissue regeneration process. [ABSTRACT FROM AUTHOR]

We consider acoustic wave transmission in a non-axisymmetric waveguide which consists of a cylindrical resonator and two cylindrical waveguides whose axes are shifted relatively to each other by an azimuthal angle Δ ϕ . Under variation of the resonator's length L and fixed Δ ϕ we find bound states in the continuum (trapped modes) due to full destructive interference of resonant modes leaking into the waveguides. Rotation of the waveguide adds complex phases to the coupling strengths of the resonator eigenmodes with the propagating modes of the waveguides tuning Fano resonances to give rise to a wave faucet. Under variation of Δ ϕ with fixed resonator's length we find symmetry protected trapped modes. For Δ ϕ ≠ 0 these trapped modes contribute to the scattering function supporting high vortical acoustic intensity spinning inside the resonator. The waveguide rotation brings an important feature to the scattering and provides an instrument for control of acoustic transmittance and wave trapping. [ABSTRACT FROM AUTHOR]

In this paper, a novel underwater unidirectional acoustic transmission (UAT) device consisting of a plate with bilateral asymmetric gratings is proposed and numerically investigated. The transmission spectra, the acoustic intensity field distributions, and the displacement field distributions are numerically calculated based on the finite element method. The transmission spectra show that the proposed device exhibits different UAT effects in three bands. The acoustic intensity field distributions demonstrate that the proposed device can realize UAT, which agree well with the transmission spectra. The mechanism is discussed by analyzing the displacement field distributions, and the UAT is attributed to the symmetric mode excited in brass plate. Furthermore, the effects of the lattice constant, the upper slit width, and the lower slit width on bands are discussed. Our design provides a good reference for designing underwater UAT devices and has potential applications in some fields, such as medical ultrasonic devices, acoustic barrier, and noise insulation. [ABSTRACT FROM AUTHOR]

We investigated the coupling effect in a pair of parallel acoustic cladded waveguides and extended the effect to obtain energy focusing in a specially structured waveguide of nested pipes. For the structure composed of two parallel waveguides, we simulated and verified that when an acoustic input wave propagates in one waveguide, the wave couples with the other and alternates between the two parallel waveguides with periodic amplitude and a well-defined coupling length. This length is related to the frequency of the input wave and the structure of the waveguide. Moreover, we fabricated a specially structured waveguide composed of four concentric circular pipes. In both simulations and experiments, we further demonstrated that the acoustic wave transmitted through designated ports of this fabricated waveguide structure can be focused onto the central waveguide with a well-defined focusing length, and that the focusing length is related to the wave frequency. Similar to its optics counterpart, not only can the coupling effect between the acoustic cladded waveguides be used in energy focusing in the nested waveguide structure, but it can also be used in other acoustic wave controlling devices, such as the frequency-selective device, the power switch for an acoustic wave, and the highly efficient pure-mode transducer. [ABSTRACT FROM AUTHOR]

High-intensity ultrasound is a technology used to improve the performance of processes in the chemical, pharmaceutical, biomass pretreatment, and food industries. However, few studies were described in the literature to comprehend the acoustic wave propagation in the material and their efficiency in the process. Thus, this study aims to determine the acoustic fields of aqueous biomass solutions from flower stalk banana using the calorimetric method and a determined sonotrode position. These tests were conducted at temperatures from 0 to 60 °C and ultrasound power from 120, 160, to 320 W. Also, the specific heat capacity and density of the solution were determined experimentally as a function of the solution concentration (0.040 to 0.100 g biomass mL−1), pH (3, 5, and 7), and temperature. The position of the thermocouple was maintained at 1 cm from the sonotrode, and the ultrasound frequency was 24 kHz. The methods and results presented in this study can be used to reproduce acoustic field calculations in aqueous biomass solutions, aiming the construction of acoustic processor systems. [ABSTRACT FROM AUTHOR]

• Oil yield was improved by 8.65–10.21% using sweeping frequency ultrasound (SFU). • Oil extraction time was shortened by 83.33% using SFU assisted method. • Acoustic field was monitored online in time and frequency domains. Sweeping frequency ultrasound (SFU) was used to assist extraction of amur grape (Vitis amurensis) seed (AGS) oil. Extraction conditions and physicochemical properties were optimized and analyzed under different extraction methods. Meanwhile, frequency and time domains were online monitored during SFU assisted extraction of AGS oil. PVDF piezoelectric sensor was used in time domain, and the hydrophone in frequency domain, so as to obtain the time–voltage waveform, signal power, spectrum distribution and other visual models. Physical models of the spatial peak acoustic intensity, charge quantity and work done by electric field force under different ultrasonic conditions were derived. The mathematical model between the work done by electric field force and the spatial peak acoustic intensity under the working state of PVDF piezoelectric sensor was constructed. Results show that the content of AGS oil by SFU assisted extraction was higher than that by organic extraction. Furthermore, the optimal single-frequency was 40 kHz and dual-frequency was 28/33 kHz, and SFU extraction time of 30 min was suitable with higher oil yield of 16.70 % and 16.94 %, respectively. In addition, the selection and combination of SFU also affected the oil oxidation degree. The peak voltage, spatial peak acoustic intensity, signal power and work of electric field force at 28/33 kHz were all higher than those at 40 kHz. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasound assisted synthesis of InV, InS and InV/InS. • Enhanced sonophotocatalytic degradation of pesticides. • Sonophotocatalytic degradation of carbofuran (97%) and diazinon (98%). • LC-MS analysis of degradation intermediates. • Detailed photocatalytic mechanism that follows type-II heterostructure. A cost effective and environmentally benign ultrasonic method has been developed for the synthesis of InVO 4 (InV), In 2 S 3 (InS) and the InVO 4 /In 2 S 3 heterostructure (InV/InS). All the designed materials were evaluated for their structural, morphological, spectroscopic, and electrochemical characterizations. Materials were examined for photocatalytic, sonocatalytic, and sonophotocatalytic degradation of carbofuran (CBF) and diazinon (DZN) pesticides under visible light. InV/InS showed enhanced degradation of CBF and DZN when compared to InV and InS. Photocatalytic degradation was accelerated by ultrasonication and found to degrade 97 and 98 % of CBF and DZN in 60 and 70 min, respectively. The reaction conditions, like pH, catalyst dosage, acoustic intensity, and ultrasound power, were carefully optimized. Electron spin resonance (ESR) spectroscopy shows the generation of superoxide radical anion and hydroxyl radicals as reactive species during photoredox reaction. The CBF and DZN degradation intermediates were analyzed using liquid chromatography mass spectroscopy (LC-MS) that shows the mineralization of the CBF and DZN to CO 2 and H 2 O. The effect of Cl−, and PO 4 3− were examined towards degradation of CBF and DZN under optimal conditions in the presence of InV/InS. The degradation of CBF and DZN is decreased in presence of Cl−, CO 3 2– and NO 3 – but PO 4 3− ions does not show any effect on degradation. The bandgap and Mott-Schottky results suggest the existence of type-II heterostructure between InV and InS through the interface. The synthesis of heterostructure and degradation of pesticides utilizes ultrasonic waves, which prove their multiple applications and attract researchers towards the effective use of sonication. [ABSTRACT FROM AUTHOR]