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DOE OSTI2020

Acoustic Energy Release During the Laboratory Seismic Cycle: Insights on Laboratory Earthquake Precursors and Prediction

Abstract Machine learning can predict the timing and magnitude of laboratory earthquakes using statistics of acoustic emissions. The evolution of acoustic energy is critical for lab earthquake prediction; however, the connections between acoustic energy and fault zone processes leading to failure are poorly understood. Here, we document in detail the temporal evolution of acoustic energy during the laboratory seismic cycle. We report on friction experiments for a range of shearing velocities, normal stresses, and granular particle sizes. Acoustic emission data are recorded continuously throughout shear using broadband piezo‐ceramic sensors. The coseismic acoustic energy release scales directly with stress drop and is consistent with concepts of frictional contact mechanics and time‐dependent fault healing. Experiments conducted with larger grains (10.5 μm) show that the temporal evolution of acoustic energy scales directly with fault slip rate. In particular, the acoustic energy is low when the fault is locked and increases to a maximum during coseismic failure. Data from traditional slide‐hold‐slide friction tests confirm that acoustic energy release is closely linked to fault slip rate. Furthermore, variations in the true contact area of fault zone particles play a key role in the generation of acoustic energy. Our data show that acoustic radiation is related primarily to breaking/sliding of frictional contact junctions, which suggests that machine learning‐based laboratory earthquake prediction derives from frictional weakening processes that begin very early in the seismic cycle and well before macroscopic failure.

58 GEOSCIENCES↗

DOE OSTI2015

Experimental observation of acoustic emissions generated by a pulsed proton beam from a hospital-based clinical cyclotron

Purpose: To measure the acoustic signal generated by a pulsed proton spill from a hospital-based clinical cyclotron. Methods: An electronic function generator modulated the IBA C230 isochronous cyclotron to create a pulsed proton beam. The acoustic emissions generated by the proton beam were measured in water using a hydrophone. The acoustic measurements were repeated with increasing proton current and increasing distance between detector and beam. Results: The cyclotron generated proton spills with rise times of 18 μs and a maximum measured instantaneous proton current of 790 nA. Acoustic emissions generated by the proton energy deposition were measured to be on the order of mPa. The origin of the acoustic wave was identified as the proton beam based on the correlation between acoustic emission arrival time and distance between the hydrophone and proton beam. The acoustic frequency spectrum peaked at 10 kHz, and the acoustic pressure amplitude increased monotonically with increasing proton current. Conclusions: The authors report the first observation of acoustic emissions generated by a proton beam from a hospital-based clinical cyclotron. When modulated by an electronic function generator, the cyclotron is capable of creating proton spills with fast rise times (18 μs) and high instantaneous currents (790 nA). Measurements of the proton-generated acoustic emissions in a clinical setting may provide a method for in vivo proton range verification and patient monitoring.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2020

A Vector Sensor-Based Acoustic Characterization System for Marine Renewable Energy

NoiseSpotter is a passive acoustic monitoring system that characterizes, classifies, and geo-locates anthropogenic and natural sounds in near real time. It was developed with the primary goal of supporting the evaluation of potential acoustic effects of offshore renewable energy projects. The system consists of a compact array of three acoustic vector sensors, which measures acoustic pressure and the three-dimensional particle velocity vector associated with the propagation of an acoustic wave, thereby inherently providing bearing information to an underwater source of sound. By utilizing an array of three vector sensors, the application of beamforming techniques can provide sound source localization, allowing for characterization of the acoustic signature of specific underwater acoustic sources. Here, performance characteristics of the system are presented, using data from controlled acoustic transmissions in a quiet environment and ambient noise measurements in an energetic tidal channel in the presence of non-acoustic flow noise. Data quality is demonstrated by the ability to reduce non-acoustic flow noise contamination, while system utility is shown by the ability to characterize and localize sources of sound in the underwater environment.

16 TIDAL AND WAVE POWER↗

DOE OSTI2025

Detecting Process Equipment Failures Using Acoustic Data and Machine Learning

Nuclear power plant (NPP) process equipment such as fans, motors, valves, and pumps generate frequent or continuous noise, and deviations from the normal operational sounds made by this equipment can indicate potential issues. These deviations can be identified via automated acoustic anomaly detection, which involves using acoustic sensors (i.e., microphones) alongside detection algorithms to continuously monitor for changes in acoustic signatures. This task is made challenging by the substantial background noise that exists, such as operators opening and closing doors, manipulating valves, and conversing—in addition to typical plant noises. In collaboration with a nuclear power utility partner, this effort assessed the efficacy of acoustic anomaly detection when using a specific acoustic sensor that compresses data into a fixed set of features that are transferable over a standard Internet of Things communication protocol, thereby improving usability but potentially degrading detection performance. Two methods of performing automated acoustic anomaly detection were evaluated: one-class support vector machine (OC-SVM) and isolation forest (iForest). To enable the use of high-quality acoustic data encompassing both normal and anomalous conditions, the study utilized the publicly available Malfunctioning Industrial Machine Investigation and Inspection dataset, which includes real measured acoustic sensor data for a range of equipment types, model numbers, and signal-to-noise ratios (SNRs), along with a benchmark set of detection results. Using this dataset, the methods were tested and then compared against the benchmark results. The results indicated that although the specific acoustic sensor did not enable as rich a feature set extraction, the proposed methods with the limited feature set performed just as well. This provides solid justification for both the methods and the use of the proposed acoustic sensor.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗

DOE OSTI2021

Systematic Design and Experimental Demonstration of Transmission-Type Multiplexed Acoustic Metaholograms

Acoustic holograms have promising applications in sound-field reconstruction, particle manipulation, ultrasonic haptics, and therapy. This study reports on the theoretical, numerical, and experimental investigation of multiplexed acoustic holograms at both audio and ultrasonic frequencies via a rationally designed transmission-type acoustic metamaterial. The proposed metahologram is composed of two Fabry–Pérot resonant channels per unit cell, which enables the simultaneous modulation of the transmitted amplitude and phase at two desired frequencies. In contrast to conventional acoustic metamaterial-based holograms, the design strategy proposed here provides a new degree of freedom (frequency) that can actively tailor holograms that are otherwise completely passive and significantly enhances the information encoded in acoustic metamaterials. To demonstrate the multiplexed acoustic metamaterial, the projection of two different high-quality metaholograms is first shown at 14 and 17 kHz, with the patterns of the letters N and S. Then, two-channel ultrasound focusing and annular beams generation for the incident ultrasonic frequencies of 35 and 42.5 kHz are demonstrated. Furthermore, these multiplexed acoustic metaholograms offer a technical advance to tackle the rising challenges in the fields of acoustic metamaterials, architectural acoustics, and medical ultrasound.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Scaling and dimensional analysis of acoustic streaming jets

This paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of the governing equations under the form of a nonlinear hydrodynamics problem coupled with an acoustic propagation problem is made on the basis of a time scale discrimination approach. This approach is preferred to the usually invoked amplitude perturbations expansion since it is consistent with experimental observations of acoustic streaming flows featuring hydrodynamic nonlinearities and turbulence. Experimental results obtained with a plane transducer in water are also presented together with a review of the former experimental investigations using similar configurations. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular, in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications, but a drawback for ultrasonic velocimetry.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

A numerically efficient damping model for acoustic resonances in microfluidic cavities

Bulk acoustic wave devices are typically operated in a resonant state to achieve enhanced acoustic amplitudes and high acoustofluidic forces for the manipulation of microparticles. Among other loss mechanisms related to the structural parts of acoustofluidic devices, damping in the fluidic cavity is a crucial factor that limits the attainable acoustic amplitudes. In the analytical part of this study, we quantify all relevant loss mechanisms related to the fluid inside acoustofluidic micro-devices. Subsequently, a numerical analysis of the time-harmonic visco-acoustic and thermo-visco-acoustic equations is carried out to verify the analytical results for 2D and 3D examples. The damping results are fitted into the framework of classical linear acoustics to set up a numerically efficient device model. For this purpose, all damping effects are combined into an acoustofluidic loss factor. Since some components of the acoustofluidic loss factor depend on the acoustic mode shape in the fluid cavity, we propose a two-step simulation procedure. In the first step, the loss factors are deduced from the simulated mode shape. Subsequently, a second simulation is invoked, taking all losses into account. Owing to its computational efficiency, the presented numerical device model is of great relevance for the simulation of acoustofluidic particle manipulation by means of acoustic radiation forces or acoustic streaming. For the first time, accurate 3D simulations of realistic micro-devices for the quantitative prediction of pressure amplitudes and the related acoustofluidic forces become feasible.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

Portable Vibro-acoustic Testing System for In Situ Microstructure Characterization and Metrology

Portable Vibro-acoustic Testing System for In situ Microstructure Characterization and Metrology James A. Smith, Corrie I. Nichol Idaho National Laboratory, Idaho Falls ID Mostafa Fatemi, Mayo Clinic, Rochester MN There is a need in research reactors like the INL to inspect irradiated materials and structures. The goal of this work is to develop a portable scanning infrastructure for a material characterization technique called vibro-acoustography (VA) that has been developed by INL [1] for nuclear applications to characterize fuel, cladding materials, and structures. The proposed VA technology is based on ultrasound and acoustic waves; however, it provides information beyond what is available from the traditional ultrasound techniques and can expand the knowledge on nuclear material characterization and microstructure evolution. VA is a three-dimensional (3D) imaging modality based on ultrasound-stimulated acoustic emission. VA uses the force caused by the beating of two frequencies to generate an acoustic emission signal. Due to absorption or reflection, the energy density in the object at an acoustic focal point changes to produce a “radiation force.” This force locally vibrates the object, which results in an acoustic field that depends on the characteristics of the object at that point. This acoustic field is detected for every point in the object; the resulting data is used to make an image of the object’s mechanical properties. This technology is fundamentally different from traditional ultrasound imaging. More specifically, VA is: (a) based on the “radiation force,” a nonlinear phenomenon in sound propagation, and (b) sensitive to both high and low frequency dynamic responses of the object. The combination of these two response types provides information about characteristics of the object beyond what is possible by traditional ultrasound imaging. High spatial resolution is achieved, since the radiation force is localized to the focal point of the ultrasound beam. Low-frequency information, which is a representative of structural characteristics, is gained through the radiation force mechanism at a low (beat) frequency. This paper will report on the development of a portable scanning that can be set up to characterize materials and component in open water reactors and canals in situ. We will show some initial laboratory results of images generated by vibro-acoustics of surrogate fuel plates and graphite structures and discus the design of the portable system. 1. Smith, J. A., and Kunerth, D. C., “Vibro-acoustic Sensors for Materials Characterization and Related Methods and Systems,” Patent Application 13226280, 09/06/2011.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Distributed Acoustic Sensing Based on Coherent Microwave Photonics Interferometry

A microwave photonics method has been developed for measuring distributed acoustic signals. This method uses microwave-modulated low coherence light as a probe to interrogate distributed in-fiber interferometers, which are used to measure acoustic-induced strain. By sweeping the microwave frequency at a constant rate, the acoustic signals are encoded into the complex microwave spectrum. The microwave spectrum is transformed into the joint time–frequency domain and further processed to obtain the distributed acoustic signals. The method is first evaluated using an intrinsic Fabry Perot interferometer (IFPI). Acoustic signals of frequency up to 15.6 kHz were detected. The method was further demonstrated using an array of in-fiber weak reflectors and an external Michelson interferometer. Two piezoceramic cylinders (PCCs) driven at frequencies of 1700 Hz and 3430 Hz were used as acoustic sources. The experiment results show that the sensing system can locate multiple acoustic sources. The system resolves 20 nε when the spatial resolution is 5 cm. The recovered acoustic signals match the excitation signals in frequency, amplitude, and phase, indicating an excellent potential for distributed acoustic sensing (DAS).

47 OTHER INSTRUMENTATION↗

DOE OSTI2018

Acoustic Monitor for Particle Size and Bed Friction in a Carbonate Fluidized Bed at High Temperature - 18014

Previous work has shown that acoustic spectra of fluidized bed pressure fluctuations show many useful bed properties [1-3]. This current work further explores the use of acoustic monitors for an 18' diameter, 66-74'' height fluidized bed at >640 deg. C. This process denitrates and agglomerates an injected sodium/aluminum nitrate aqueous simulant and produces at steady-state a denitrated product of 200-300 micron sodium carbonate/aluminate particles. The fluidized bed shows characteristic acoustic resonances around 1-2 Hz in the FFT (Fast Fourier Transform) of pressure fluctuations for each of three taps at fluidized bed heights of 12'', 39'', and 58''. The acoustic resonance spectra depend on a bed friction that once calibrated, monitors the HMPD (harmonic mass mean particle diameter or Sauter mean diameter) along with other important bed properties. This fluidized bed operates at high temperature with an evolving HMPD that can be steady state with an appropriate superficial spatial velocity (SSV). The acoustic FFT integrated power spectrum, IPS, of pressure fluctuations represents the bed-friction damped RMS (root mean square) pressure fluctuations at each tap. The transition from a static to fluidized bed at each bed height occurs when the damped bed RMS pressure fluctuations are greater than the static head (the FFT zero Hz designated zero Hz proportional to FFT zero Hz) at that bed height. A bed will de-fluidize and become static at a bed height when bed friction completely dampens the RMS pressure fluctuations, which occurs for decreasing particle size among other factors. The ratio IPS/zero Hz then provides a continuous monitor of bed friction damping as well as particle size as the HMPD. Since HMPD and bed friction damping are both very important parameters for fluidized particle beds, the acoustic HMPD and bed friction damping both provide very useful monitors for fluidized bed operation. Such acoustic monitors have shown that they are especially sensitive to the presence of very fine particles in the bed of less than 50 microns diameter. Acoustic monitors for particle size and bed friction damping will be very useful in any fluidized bed, especially fluidized beds where particle size changes. The fluidized bed friction damping depends on many other bed properties besides particle size such as bed height, density, SSV, void fraction, gas viscosity, and fluidization scheme and so acoustic bed friction should also be useful for monitoring other bed properties besides particle size. In fact, the change in the static bed friction slope with SSV upon fluidization follows the Ergun function and reveals a minimum fluidization velocity for each HMPD. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

MO-A-BRD-07: Feasibility of X-Ray Acoustic Computed Tomography as a Tool for Calibration and In Vivo Dosimetry of Radiotherapy Electron and Photon Beams

Purpose: This work simulates radiation-induced acoustic waves to assess the feasibility of x-ray acoustic computed tomography (XACT) as a dosimeter. XACT exploits the phenomenon that acoustic waves with amplitude proportional to the dose deposited are induced following a radiation pulse. After detecting these acoustic waves with an ultrasound transducer, an image of the dose distribution can be reconstructed in realtime. Methods: Monte Carlo was used to simulate the dose distribution for monoenergetic 6 MeV photon and 9 MeV electron beams incident on a water tank. The dose distribution for a prostate patient planned with a photon 4-field box technique was calculated using clinical treatment planning software. All three dose distributions were converted into initial pressure distributions, and transportation of the induced acoustic waves was simulated using an open-source toolkit. Ideal transducers were placed around the circumference of the target to detect the acoustic waves, and a time reversal reconstruction algorithm was used to obtain an XACT image of the dose for each radiation pulse. Results: For the photon water tank relative dosimetry case, it was found that the normalized acoustic signal amplitude agreed with the normalized dose at depths from 0 cm to 10 cm, with an average percent difference of 0.5%. For the reconstructed in-plane dose distribution of an electron water tank irradiation, all pixels passed a 3%–3 mm 2D gamma test. The reconstructed prostate dose distribution closely resembled the plan, with 89% of pixels passing a 3%–3 mm 2D gamma test. For all situations, the amplitude of the induced acoustic waves ranged from 0.01 Pa to 1 Pa. Conclusion: Based on the amplitude of the radiation-induced acoustic waves and accuracy of the reconstructed dose distributions, XACT is a feasible technique for dosimetry in both calibration and in vivo environments for photon and electron beams and merits further investigation. Funding from NSERC, CIHR and McGill University. SH acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290)

60 APPLIED LIFE SCIENCES↗

DOE OSTI2011

Apparatus for separating particles utilizing engineered acoustic contrast capture particles

An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

42 ENGINEERING↗

DOE OSTI2013

Device and method for generating a beam of acoustic energy from a borehole, and applications thereof

In some aspects of the invention, a method of generating a beam of acoustic energy in a borehole is disclosed. The method includes generating a first acoustic wave at a first frequency; generating a second acoustic wave at a second frequency different than the first frequency, wherein the first acoustic wave and second acoustic wave are generated by at least one transducer carried by a tool located within the borehole; transmitting the first and the second acoustic waves into an acoustically non-linear medium, wherein the composition of the non-linear medium produces a collimated beam by a non-linear mixing of the first and second acoustic waves, wherein the collimated beam has a frequency based upon a difference between the first frequency and the second frequency; and transmitting the collimated beam through a diverging acoustic lens to compensate for a refractive effect caused by the curvature of the borehole.

47 OTHER INSTRUMENTATION↗

DOE OSTI2014

Apparatus for separating particles utilizing engineered acoustic contrast capture particles

42 ENGINEERING↗

DOE OSTI2016

Apparatus for separating particles utilizing engineered acoustic contrast capture particles

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2018

Systems and methods for separating particles utilizing engineered acoustic contrast capture particles

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Empirical Acoustic Source Model for Chemical Explosions in Air

Chemical explosions generate pressure disturbances in air that radiate as nonlinear shock waves near the source and transition into acoustic waves with distance. Because low-frequency acoustic waves generally travel large distances without significant loss of energy, they are often used for explosion monitoring and yield estimation. However, quantitative relationships between acoustic energy and explosion yields are required for accurate yield estimation. Here, we develop an empirical acoustic source model for chemical explosions from experimental data. The empirical model returns the acoustic pressure waveform for the detonation of 1 kg of trinitrotoluene, which is conventionally used to represent the explosive release of 4.184 MJ of explosion energy. The full-waveform model can be used to predict acoustic signals for an arbitrary yield of a high-explosive detonation based on the standard scaling law and to estimate acoustic energies in a specific frequency range. We evaluate the accuracy of the acoustic source model independently by estimating the yield of other explosive events that are not included in the model development. Finally, statistical characteristics of the model and their implications for the uncertainty quantification of estimated yields are discussed.

58 GEOSCIENCES↗

DOE OSTI2026

Establishing an acoustic-property relationship in laser powder bed fusion with machine learning

Quality control of Laser Powder Bed Fusion (PBF-LB) additively manufactured parts is an important hurdle inhibiting the technology’s use structural applications. Acoustic monitoring of the laser powder bed fusion process can detect defects in-situ that are known to degrade mechanical properties. However, processing-structure-property (PSP) relationships are required to extrapolate from detected defects to part performance. Here, this study explores how acoustics may be a suitable signature linking processing conditions to properties, thus effectively substituting for structure in the PSP relationship. Establishing such a relationship would enable a part’s mechanical performance to be directly predicted from its acoustic signature, reducing the need for destructive testing or microstructural analysis to ensure a part will meet performance requirements. One hundred CoCrFeMnNi high entropy alloy tensile bars were printed across 13 process conditions in a series of 6 prints. The acoustic signatures of these tensile bars were used to train machine learning models to predict each part’s mechanical properties. By using both process information and acoustic information to predict mechanical properties, yield strength was predicted 18% more accurately and ductility to failure was predicted 10% more accurately than is achieved when using duplicate parts to predict part performance. Finally, individual acoustic frequencies were investigated to determine why acoustic signatures improve mechanical property predictions and the potential physical origins of these signatures. This work demonstrates how blending acoustics, process information, and machine learning can provide in-situ diagnostics of mechanical properties and improve the reliability of the PBF-LB process.

Acoustic emission↗