Acoustic Experiments Research Articles

A Pitch-Matched Transceiver ASIC With Shared Hybrid Beamforming ADC for High-Frame-Rate 3-D Intracardiac Echocardiography

In this article, an application-specific integrated circuit (ASIC) for 3-D, high-frame-rate ultrasound imaging probes is presented. The design is the first to combine element-level, high-voltage (HV) transmitters and analog front-ends, subarray beamforming, and in-probe digitization in a scalable fashion for catheter-based probes. The integration challenge is met by a hybrid analog-to-digital converter (ADC), combining an efficient charge-sharing successive approximation register (SAR) first stage and a compact single-slope (SS) second stage. Application in large ultrasound imaging arrays is facilitated by directly interfacing the ADC with a charge-domain subarray beamformer, locally calibrating interstage gain errors and generating the SAR reference using a power-efficient local reference generator. Additional hardware-sharing between neighboring channels ultimately leads to the lowest reported area and power consumption across miniature ultrasound probe ADCs. A pitch-matched design is further enabled by an efficient split between the core circuitry and a periphery block, the latter including a datalink performing clock data recovery (CDR) and time-division multiplexing (TDM), which leads to a 12-fold total channel count reduction. A prototype of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8{\times }9$ </tex-math></inline-formula> elements was fabricated in a TSMC 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> HV BCD technology and a 2-D PZT transducer matrix with a pitch of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$160 \mu \text{m}$ </tex-math></inline-formula> , and a center frequency of 6 MHz was manufactured on the chip. The imaging device operates at up to 1000 volumes/s, generates 65-V transmit pulses, and has a receive power consumption of only 1.23 mW/element. The functionality has been demonstrated electrically as well as in acoustic and imaging experiments.

Robustness of Reduced-Order Jet Noise Models

Three statistical jet noise prediction models are compared for a representative set of single-stream jet cases, which include cold and hot jets of the Strategic Investment in Low-Carbon Engine Technology experiment at an acoustic Mach number of 0.875 as well as the cold jets of the NASA small hot jet acoustic rig experiment at acoustic Mach numbers of 0.5 and 0.9. The implemented models are those proposed by Tam and Auriault (Jet Mixing Noise from Fine-Scale Turbulence,” AIAA Journal, Vol. 37, No. 2, 1999, pp. 145–153), Khavaran and Bridges (“An Empirical Temperature Variance Source Model in Heated Jets,” NASA TM 2012-217743, 2012), and the Goldstein’s “A Generalized Acoustic Analogy,” Journal of Fluid Mechanics, Vol. 488, July 2003, pp. 315–333) generalized acoustic analogy (GAA) model. By virtue of reduced-order modeling, which is based on the single-point mean flow and turbulence statistics, all of these implementations use a number of empirical dimensionless source parameters for far-field noise spectra predictions. In comparison with the Tam and Auriault model, the Khavaran and GAA model implementations use several dimensionless parameters, which are available from previous literature and assumed to be more or less universal for a class of single-stream jets. These parameters include the fluctuating enthalpy function and the dimensionless amplitudes of autocovariances of turbulent fluctuating stresses and velocities available from the literature. The comparison of the three models is aimed at not only assessing their accuracy for a range of jet conditions, observer angles, and frequencies but also to examine their robustness outside of a reference jet experiment for which their source models were calibrated. For the input to each model, the mean flow, turbulence kinetic energy, and dissipation rate extracted from Large Eddy Simulations and Reynolds-averaged Navier–Stokes solutions are considered.

Vector Sensor Steering-Dependent Performance in an Underwater Acoustic Communication Field Experiment.

This paper shows the performance resulting from combining vector sensor directional components in an underwater acoustic communication experiment. The objective is to relate performance with transmission direction and range. Receiver structures based on beamforming and passive time-reversal are tested in order to quantify and compare the steerability impact of vector sensor directional components. A shallow water experiment is carried out with a bottom fixed two-axis pressure-gradient vector sensor. A ship suspended acoustic source transmits coherent modulated communication signals at various ranges and from several directions. Results show that one vector sensor can provide an up to 10 times smaller error bit rate than a pressure sensor, favoring communication robustness without size penalty.

Study on Microscopic Characteristics of Spatial Distribution of Fractures in Deteriorated Sandstone

In the underground environment with large buried depth and high ground stress, man-made disturbance is very easy to cause the rapid expansion of primary fractures in the rock, and then developed into the macrodynamic performance of rock. Based on the propagation law of elastic waves in discontinuous media, the application of acoustic emission detection technology can quickly determine whether there are primary fractures in the rock and predict its approximate location. In this work, CT scanning experiments of intact sandstone specimens and fractured sandstone specimens were performed. The gray value distribution of intact sandstone specimens and fractured sandstone specimens was studied. The sandstone specimens were divided into 4 zones (I~IV) from top to bottom. The height of each zone is from 0 mm to 25 mm, and the upper end face of each zone is the starting face. Acoustic emission experiments of intact sandstone and fractured sandstone are carried out based on the equilateral triangle sensor array. The dispersion of AE wave velocity and amplitude in intact sandstone specimens and fractured sandstone specimens is studied. The results show that the crack evolution law of sandstone specimens before and after preloading is closely related to the density distribution. The regular trend is from low density to high density. And the decay law of AE eigenvalue before and after preloading of sandstone specimen is consistent with the change trend of gray value. This shows that it is feasible to explore the spatial location of primary fractures and the degree of development of primary fractures in the rock through the equilateral triangle sensor array. In the actual project, it can provide some guidance and suggestions for related projects.

Experimental observation and theoretical analysis of the low-frequency source interferogram and hologram in shallow water

The interference pattern of the sound field of a broadband source in a shallow water waveguide is studied theoretically and experimentally in this paper. In the ocean waveguide, the sound source generates the interference pattern of the intensity distribution (interferogram) in the frequency–time domain. The mathematical theory of the interferogram structure is developed. The source interferogram consists of a set of quasi-parallel interference fringes in the frequency–time domain. It is shown that the slope of the interference fringes depends on the distance, velocity, and direction of motion of the sound source. The relationship between the slope angle of the interference fringes in the interferogram and the source parameters is derived in the paper. The two-dimensional Fourier transform (2D-FT) is used to analyze the interferogram. The result of the 2D-FT is called the Fourier hologram (hologram). It is shown that the hologram consists of a few focal spots in a relatively small area. The presence of these focal spots is the result of the interference of acoustic modes with different wavenumbers. The mathematical theory of the hologram structure is developed in this paper. The relationship between the coordinates of the focal spots on the hologram and the source parameters is considered. Consequently, the position of the focal spots can be used to estimate the source parameters (range, velocity, and direction of motion). The theoretical conclusions are verified in the context of computer modeling and the results of the acoustic experiment on the Pacific shelf (Yellow Sea, April, 2004) in the band 180–220 Hz.

A comparative study of four types of multi-scale entropies in feature extraction of underwater acoustic signals for potential GNSS positioning applications

The combination of underwater acoustic processing and the Global Navigation Satellite System (GNSS) has achieved remarkable economic benefits in offshore operations. As the key technology of GNNS positioning, feature extraction of underwater acoustic signals is affected by the complex marine environment. To extract more effective information from underwater acoustic signals, we use four types of multi-scale entropies, including multi-scale sample entropy (MSE), multi-scale fuzzy entropy (MFE), multi-scale permutation entropy (MPE), and multi-scale dispersion entropy (MDE), to analyze and distinguish underwater acoustic signals. In this study, two groups of real-word underwater acoustic signal experiments were performed for feature extraction of ship-radiated noises (SRNs) and ambient noises (ANs). The results indicated that the performance of the MFE-based feature extraction method is superior to that of feature extraction methods based on the other three entropies under the same number of features, and the highest average recognition rate (ARR) of the MFE-based feature extraction method for SRNs reaches 100% when the number of features is 3.

Analysis of noise attenuation for offshore platform silencer in duct with flow

Recently, the NORSOK standards, which regulate noise and vibration on offshore platforms, were strengthened by prohibiting the use of glass wool for environmental and safety reasons. In addition, the use of sound-absorbing materials in panels and silencers was prohibited. Therefore, developing a silencer that does not use sound-absorbing materials is necessary. In this study, a bandgap expressed by acoustic characteristics of a periodic structure was applied to develop a silencer without sound-absorbing materials. The bandgap is formed in a frequency range in which propagation of acoustic waves is suppressed by setting a specific distance between single units based on periodic structural theory. The designed silencer evaluates the noise attenuation effect of the periodic structure based on a fluid-structure coupling finite-element equation for a plane wave in a stationary medium. In addition, the silencer model was selected by analyzing the regenerated noise originating from the periodic structure in the flow duct. This flow noise is used to analyze the propagation of sound waves based on the FW-H equation. This is achieved by employing the Lighthill acoustic analogy to predict the flow-induced sound pressure. Furthermore, compressed air was injected at the end of the duct in the flow noise experiment to perform measurements. The results from the acoustic and flow noise experiments were compared to confirm the effect of the flow in the duct on noise generation. Moreover, the flow noise analysis based on the flow velocity elucidated the effect of the periodic structure on the flow. In addition, the analysis results were used to investigate its performance of the silencer with the periodic rod arrangement considering the flow noise in the duct and predict its acoustic characteristics in the bandgap frequency range.

The coordinated arctic acoustic thermometry experiment—CAATEX

The coordinated arctic acoustic thermometry experiment (CAATEX) was a joint U.S.-Norwegian trans-Arctic acoustic propagation experiment with a design comparable to the 1994 TransArctic Propagation (TAP) experiment. The goal was to measure the changes in low-frequency sound propagation due to changes in ocean heat content and salinity, and ice conditions. Two 35 Hz acoustic transceiver moorings, one in the Nansen Basin and one in the Beaufort Sea, were deployed along with four other receiving moorings. All six moorings were equipped with vertical hydrophone arrays, recording transmissions every 36 h from fall 2019 to fall 2020. Each mooring also recorded temperature and salinity time series along the vertical extent of the hydrophone arrays, ice thickness using an upward-looking sonar, and ocean bottom pressure. The acoustic travel-times allow comparison of present-day heat content to the 1994 measurement, but there are several other points of comparison that are sensitive to environmental changes. These include transmission loss, acoustic scattering, and the acoustic arrival structure. These measurements of ocean and ice processes, and the acoustic propagation and ambient sound will improve our ability to monitor, communicate, and navigate in the Arctic Ocean.

Travel-time variability during the 2016–2017 deep-water Canada Basin Acoustic Propagation Experiment

The Arctic Ocean is undergoing dramatic changes in response to increasing atmospheric concentrations of greenhouse gases. The decreases in ice extent, the near disappearance of multiyear ice, and changes in the stratification of the ocean all have important implications for underwater acoustic propagation. During the 2016–2017 Canada Basin Acoustic Propagation Experiment (CANAPE), a long vertical receiving array was embedded within an ocean acoustic tomography array of six acoustic transceivers with a radius of 150 km. The impulse response of the ocean was measured every four hours using broadband signals centered at about 250 Hz. The observed travel-time variability was extraordinarily low, reflecting both the low internal-wave energy level and sparseness of mesoscale eddies in the Canada Basin. The peak-to-peak travel time variability of the early, resolved ray arrivals was only a few tens of milliseconds, and the standard deviations over the entire year were only a few milliseconds. The travel-time spectra show increasing energy at lower frequencies and enhanced semidiurnal variability, presumably due to some combination of the semidiurnal tides and inertial variability. The travel-time fluctuations are roughly an order of magnitude smaller than is typical in midlatitudes at similar ranges.

Ambient sound observations from beamformed horizontal array data in the Pacific Arctic

Changes in the Arctic environment with regard to declining sea ice and changing oceanography are expected to alter the ambient sound field, affecting both the sound generating processes and the acoustic propagation. This talk presents acoustic recordings collected on the 150-m isobath on the Chukchi Shelf during the Canada Basin Acoustic Propagation Experiment (CANAPE), which took place over a yearlong period spanning October 2016 to October 2017. The data were recorded on a 52-channel center-tapered horizontal line array and adaptively beamformed to quantify the azimuthal directionality in long-term trends ambient sound under 1200 Hz as well as track specific sound events as they travel through space over time. The acoustic data were analyzed in the context of wind speed and satellite imagery to identify the dominant sound generation mechanisms. Automated identification system (AIS) data were also incorporated to determine sources of ship generated sound and seismic profiler activity observed in the acoustic recordings. This talk will provide an overview of the long-term trends and describe a subset of results from the beamforming. [Work Supported by ONR.]

Acoustic networks in high Arctic Ocean observing systems

Sustained in situ ice-ocean observations are sorely lacking in the Arctic, limiting research on climate, weather, ice-ocean processes, and geophysical hazards. A sustained network of advanced multipurpose underwater moorings and drifting buoys in the Nansen and Amundsen Basins that included acoustic and other instrumentation would make a substantial contribution to a high Arctic Ocean observing system. Such a network would provide point measurements of ocean parameters, large-scale temperature measurements using acoustic thermometry, acoustic geo-positioning of underwater floats and gliders, and passive acoustic measurements for detection of marine mammals, geohazards, and human generated noise. Optimal design of such a network of fixed moorings and drifting platforms requires accurate knowledge of the ice-ocean environment to determine the acoustic properties. Such a sustained network would build on the successful basin-wide coordinated arctic acoustic thermometry experiment (CAATEX). In this presentation, the focus will be on the oceanographic and acoustic characteristics of the Nansen and Amundsen Basins using observations made during CAATEX. The ability of several climate models and reanalysis products to describe the oceanographic characteristics as well as their usefulness in predicting low-frequency acoustic propagation will be evaluated.

Statistical and spatial characteristics of ocean ambient noise up to 1900 Hz on the Chukchi Shelf in the Arctic affected by climate change

This paper analyzes a year of underwater ambient noise data recorded in the Arctic on the Chukchi Shelf as part of the 2016–2017 Canada Basin Acoustic Propagation Experiment (CANAPE). A broadband (50–1900 Hz) statistical study is performed to analyze noise variability and its relationship to environmental drivers, notably the local presence of ice and the presence/absence of the Beaufort duct in the experimental area. Both environmental factors are found to significantly affect the noise levels. Local ice coverage tends to decrease ambient noise at all frequencies, while the presence of the Beaufort duct tends to increase ambient noise for frequencies below 1 kHz. The lowest ambient noise levels are, thus, found when the sea is ice covered, but the duct is absent. Furthermore, the study explores the link between noise level and distant ice drift magnitude. The ambient noise levels are shown to be highly correlated with distant (up to 1400 km) ice drift for frequencies between 300 and 1500 Hz. [Work supported by the Office of Naval Research.]

Under-ice 4-8 kHz acoustic transmission and communication in ducted environments in the Arctic Ocean

Underwater communications and navigation for small platforms can typically involve acoustic systems operating at kHz frequencies. For under-ice applications, this motivates studies of acoustic transmission in present-day Arctic conditions. This paper presents data from recent mid-frequency (4–8 kHz) under-ice acoustic transmission and communication experiments to ∼10 km range in the Nansen Basin and in the Beaufort Sea of the Arctic Ocean. For shallow sources and receivers, delay profiles show early arrivals due to ducted paths followed by a group of strong arrivals due to bottom-interacting paths. The relative amplitudes of these groups depend on duct and under-ice properties. We demonstrate that despite shallow (∼25 m) source/receiver depths, good communication performance can be achieved in these single- and double-ducted environments by exploiting the bottom-interacting paths. Simulations with the Bellhop ray model support the findings.

Broadband sound speed and attenuation of a mud layer from acoustic propagation experiments in the New England Mud Patch

A series of Seabed Characterization Experiments (SBCEX) have been conducted in the New England Mud Patch area, where a top mud layer overlays a sand sediment. Using broadband acoustic signals from the SBCEX, the sound speed and attenuation of the mud layer as a function of frequency (from a few tens of Hz up to around 1 kHz) have been estimated by various inversion algorithms based on (1) modal dispersion curves and transmission loss [reported at the ASA Spring meeting, 2016], (2) Airy phase [Spring, 2017], (3) modal amplitude [Fall, 2017], (4) spatial coherence measurements [Spring, 2018], (5) mid-frequency modal dispersion analysis [Fall, 2019], and (6) ground waves [Fall, 2022]. This paper summarizes these inverted sound speed and attenuation, which are obtained at various frequencies independently (without using the frequency dependent constraints from any geo-acoustic models), therefore the inverted results could be used to verify the validity of geo-acoustic models. The performances of these inversion methods are evaluated. The performance assessment is helpful for one to select appropriate inversion algorithms and to choose optimal acoustic data for geo-acoustic inversion. [Work supported by ONR Ocean Acoustics.]

Assessing the effect of poly (ethylene oxide-b-lactide) block copolymer on the characteristics of perfluoropentane phase-shift nanoemulsions

Acoustic droplet vaporization is the ultrasound-mediated phase shift of liquid perfluorocarbon emulsions into echogenic microbubbles. To reduce the emulsion's interfacial surface tension and minimize coalescence, the perfluorocarbon is coated with a surfactant. Copolymer shelled phase-shift nanoemulsions have emerged as potential diagnostic and therapeutic agents. The goal of this study is to understand how adding Poly (ethylene oxide-b-lactide) (PEO-PLLA) to a Pluronic F-68 shell formulation impacts the perfluoropentane (PFP) nanoemulsion size and polydispersity index (PDI). PFP nanoemulsions coated with Pluronic F-68 or a Pluronic F-68: PEO-PLLA (1:0.05 (v/v)) blend was prepared using high shear pressure homogenization (LV1, Microfluidics International, Corp.). Nanoemulsion size distributions and concentrations were measured (n=5) using a Beckman Coulter Multisizer 4. At 10,000 psi pressure and 1 passage through the homogenizer, the copolymer blend and Pluronic F-68 nanoemulsions had modal diameters of 0.73 ± 0.09 μm and 1.25 ± 0.09 μm, respectively. Additionally, the concentration was larger (6.6 ± 0.1×10−2 vs 5.56 ± 0.2×10−2 ml/ml) and the PDI smaller (0.070 ± 0.004 vs 0.129 ± 0.004) for the copolymer blend. All differences were statistically significantly different (p &amp;lt; .05). The inclusion of PEO-PLLA with Pluronic F-68 reduced the PFP nanoemulsion size and polydispersity, which may reduce experimental variability in acoustic droplet vaporization experiments.

Ocean acoustic tomography in the Beaufort Gyre

An ocean acoustic tomography array with a radius of 150 km was installed in the central Beaufort Gyre during 2016–2017 for the Canada Basin Acoustic Propagation Experiment (CANAPE). Five transceivers were deployed in a pentagon shape with a sixth transceiver at the center and a long vertical receiving array northwest of the central mooring. At least 12 refracted-surface-reflected (RSR) ray arrivals with lower turning points at depths between 500 and 3500 m were resolved in the acoustic receptions at all receivers. Travel-time anomalies were computed relative to a range-dependent sound-speed reference made by objectively interpolating annual-average sound-speed profiles constructed from the temperature data at each mooring. The travel time anomalies were inverted to estimate the 3-D sound-speed anomaly, including corrections to the positions of sources and receivers consistent with the uncertainty from long-baseline acoustic navigation systems at each mooring. Although the deep water in the Canada Basin is nearly homogeneous in temperature and salinity and highly stable (slowly warming in response to geothermal heating), it proved necessary to allow for a sound-speed change in the deep ocean to obtain consistent inversions, suggesting that the sound-speed equation at high pressure and low temperature is in error by about 0.1–0.2 ms−1.

Acoustic propagation and ambient sound on the Chukchi shelf

This paper presents a yearlong record of acoustic propagation and ambient sound collected on the Chukchi Shelf collected as part of a set of experiments known as the Canada Basin acoustic propagation experiment (CANAPE) and shallow-water CANAPE which took place from 2016 to 2017. Over the course of the yearlong experiment, the surface conditions transitioned from completely open water to fully ice-covered. The propagation conditions in the deep basin were dominated by a subsurface duct; however, over the slope and shelf, the duct was seen to significantly weaken during the winter and spring. The combination of these surface and subsurface conditions led to changes in the received level of the deep-water tomography sources that exceeded 60 dB. The ambient sound data were analyzed using k-means clustering to quantify the occurrence of six spectral shapes over the yearlong experiment. Each cluster type was associated with a different sound generation process based on the correlations with environmental observations. The cluster observed most frequently was associated with wind-generated sound, and the cluster with the smallest number of observations was attributed to wind effects on frazil ice forming in open leads during the ice-covered season. [Work sponsored by ONR.]

Acoustic receptions at close ranges measured on autonomous underwater vehicles in the Beaufort Sea

Rapid warming of the Pacific Summer Water layer strengthens a subsurface duct in the Beaufort Sea, allowing for long-range propagation at low frequencies. An array of tomography sources was deployed within the duct as part of the Canada Basin Acoustic Propagation Experiment (CANAPE) to study acoustic propagation in this environment. The moored transceivers provide measurements of acoustic propagation at several ranges from 176 to 285 km. Additionally, two Seaglider vehicles equipped with hydrophone receivers navigated in and around the CANAPE array and recorded the transmissions from the moored sources at ranges as far as 530 km and as close as 2 km. A spatially variable sound speed environment was generated from in-situ data measured by the Seagliders and CTD casts from research vessels. Acoustic arrivals measured on the vehicles were matched to range-dependent acoustic predictions made with a broadband Parabolic Equation model to estimate source-receiver range. Acoustic receptions from multiple moored sources were used to localize the Seagliders. Here, we examine the close range (2–25 km) receptions and their impacts on acoustic localization.

The Effect of Directional Ambient Noise on an Underwater Acoustic Link in Shallow Environments

To evaluate the performance of underwater acoustic communication systems, it is typically assumed that the noise at the receiver is uncorrelated spatially and temporally. This assumption underestimates the impact of acoustic ocean ambient noise on the performance of communication systems. In this article, the impact of ocean ambient noise on a coherent acoustic communication system is analyzed. The communication performance is assessed in narrowband conditions at a center frequency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\text{2.048}\;\text{kHz}}$</tex-math></inline-formula> using the noise measurements from two different experiments—DalComm1 and the shallow water Canada Basin acoustic propagation experiment (SW CANAPE). DalComm1 focuses on characterizing the acoustic channel over ranges of 1–10 km on the Nova Scotian littoral, while the spatio-temporal variability of noise propagation in shallow and deep water environments was characterized during the CANAPE experiments. The ambient noise coherence and directionality in both environments were also measured. Two distinct noise modeling methodologies are presented to represent realistic synthetic ambient noise with defined directionality. Further, the synthetic noise is validated against measured ambient noise. The impact of ambient noise characteristics on an optimum space-time filter is characterized. A frame structure with an optimum training duration is also defined for the adaptive filter. It is observed that the bit-error rate of the space-time filter depends on optimizing the training and payload duration in the received signal.

Influence of stratified sub-bottom sediment layers on acoustic simulations in the New England shelf break environment

During the 2021 New England Shelf Break Acoustics (NESBA) Experiment, a large number of acoustic signal transmissions along and across the continental shelf were compared with combined physical oceanographic (PO) and ocean acoustic (OA) models. This experiment aimed to examine the influence of environmental changes in the water column on acoustic propagation in the shelf break environment. Sub-bottom surveys carried out by a combination of autonomous underwater vehicles (AUVs) and ship-board instruments revealed distinctly stratified sediment layers. Accounting for the properties of sub-bottom sediment layers is an integral component of diagnosing mismatch between experimental acoustic data and simulations, as these properties can influence the attenuation and scattering of received signals. A comparison of homogeneous half-space bottom models calculated at sea in May of 2021 and improved models which incorporate the results of sub-bottom surveys is presented, and the importance of this modeling consideration is examined for the purposes of data and model comparisons. [This work was supported by the Office of Naval Research.]