The primary goal of this thesis is to utilize acoustical radiation from the Arctic ice cover to infer the response of sea ice to environmental forcing, and to sense remotely the mechanical properties of the ice. The work makes use of two experiments in the Canadian arctic undertaken by the Ocean Acoustics Group of the Institute of Ocean Sciences, which resulted in an extensive body of acoustical and related environmental data. Cracking sounds originating from both first and multi-year ice fracturing processes are analyzed. Data used in this thesis also include sound made by artificial sources. The survey of in situ ice conditions by air photography and synthetic radar imaging, and a crack distribution map based on observations made with a 3-D hydrophone array, reveal, for the first time, a close correlation between thermal cracking events and ice type. It is shown that most of the thermal cracks occur in irregular multi-year ice where there are exposed, snow-free surfaces. The study shows that acoustical radiation from some cracks implies a slip-stick seismic movement over the faults, and some cracks tend to radiate more high frequency sound downwards rather than sideways. This phenomenon is most clearly apparent in sounds made by artificial sources. Another interesting finding from this study is that the sound of cracking ice does not always exhibit a vertical dipole radiation pattern, and some cracks due to thermal tension on smooth first year ice radiate more energy horizontally. The observations have motivated the development of various analytical models. These models allow the observed acoustical features to be related to the length and depth of a crack, the thickness of the ice cover and its Young's modulus. The models also show that maximum sound radiation from a crack is in the direction of external forcing. Finally, it is found that noise due to rubbing between ice floes exhibits a narrow band spectrum. This phenomenon is investigated and a linear model derived shows that the observed peak frequency is that of the first mode horizontal shear wave triggered by frictional effects at the ice floe edge. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Small-amplitude, high-frequency (ultrasound) forcing of fluid/particle systems is being used in a number of applications associated with non-destructive fluid mixing and the movement/manipulation of particles in suspension. Of most importance in this context are the second-order, steady, effects arising from the nonlinear interaction of a leading-order oscillatory field with itself. In this thesis we consider some of these steady effects in both incompressible and compressible fluids. We first consider the axisymmetric steady streaming generated in an incompressible, viscous fluid contained between two (radially) infinite parallel plates, each oscillating in a direction normal to its own plane. In the limit of small-amplitude, high-frequency oscillations, we show that the steady-streaming flow in the fluid bulk is driven by thin streaming sublayers at the plates, at which the normal velocity is zero and the radial velocity varies linearly with distance from the axis of rotational symmetry. Effectively, in the bulk flow, the bounding plates appear as (no-slip) impermeable walls that stretch radially. This bulk-flow problem is extended to allow for the analogous steady flow of two immiscible, incompressible, viscous fluids, each undergoing a radial-stretching motion appropriate to high-frequency steady streaming. For a flat interface between the fluids, a self-similar solution reduces the Navier--Stokes equations to a nonlinear boundary-value problem, the solution of which exhibits an interesting structure in the limit of large Reynolds number. In this limit, solutions can be found using matched asymptotic expansions, but the location of the interface between the fluids can only be determined if terms that are exponentially small in the Reynolds number are included. It is shown that for fluids of almost-equal densities, exponentially-small differences can have a leading-order effect on the observed flow. The second part of the thesis is concerned with the (steady) acoustic radiation force on a rigid sphere submerged in a compressible, inviscid fluid, when the wavelength of the incident acoustic field is large compared to the radius of the sphere. In this limit, a matched asymptotic expansion method is used to derive an expression for the acoustic radiation force, on both fixed and free rigid spheres, due to a range of incident fields. For incident acoustic fields that are appropriate to planar and circular waveguides/channels, expressions are derived for the scattered field and the radiation force on a rigid sphere in the long-wavelength limit. Fixed and free spheres located both on and off the axis of symmetry of these incident fields are considered. This is an extension to the current literature, in which numerical methods are used to examine the scattering from spheres in an off-axis position, and problems are restricted to the consideration of fixed spheres only. It is shown that there are stable and unstable positions within the waveguide where any off-axis acoustic radiation force vanishes, leaving only an along-channel component. For free spheres, these positions are shown to be dependent on the relative particle density and it is suggested that this may allow for a mechanism to sort such small particles radially in a circular waveguide, if secondary scattering effects are neglected.

Dissipation is an inevitable property of a mechanical system and influences the dynamical behavior and device performance. It is, therefore, crucial to study and understand the sources of dissipation in mechanical systems in order to control the dissipation present in the system. These sources of dissipation can be broadly classified in two groups: extrinsic and intrinsic mechanisms. Extrinsic mechanisms are independent of material properties and influenced by the external properties of the system, such as geometry, pressure, and temperature. Intrinsic mechanisms on the other hand, are independent of external conditions and arise from the intrinsic properties of the device material, such as defects in the bulk and the surface of the material. In this work, we closely study two extreme limits of dissipation at the opposite ends of the spectrum. First, at the high dissipation limit where extrinsic mechanisms dominate dissipation, spectral properties of the thermal noise force giving rise to Brownian fluctuations of a continuous mechanical system — namely, a doubly clamped nanomechanical beam resonator — immersed in a viscous liquid are investigated. To this end, two separate sets of experiments are performed. The power spectral density (PSD) of the Brownian fluctuations of the resonator around its fundamental mode are measured at the center of the resonator. Then, the frequency-dependent linear response of the resonator is measured, again at its center, by driving it with a harmonic force, via an electrothermal transducer, that couples well to the fundamental mode. These two separate measurements are then used to determine the PSD of the Brownian force acting on the structure in its fundamental mode. The PSD of the force noise extracted from multiple resonators with varied lengths spanning a broad frequency range displays a ``colored spectrum'' and follows the viscous dissipation of a cylinder oscillating in a viscous liquid by virtue of the fluctuation-dissipation theorem. In the second application, which is at the ultra-low dissipation limit at low temperature where intrinsic mechanisms dominate dissipation, we design and fabricate high-frequency aluminum nitride (AlN) piezo-optomechanical resonators. Furthermore, an acoustic radiation shield consisting of periodic phononic crystals is designed and implemented to further decrease dissipation. Fabrication and design of both the optomechanical cavity and phononic crystals are discussed in detail. Room temperature characterization of the ring resonator is presented and out-of-plane thickness mode of the AlN resonators has been identified. With microwave mechanical frequency and high Quality factor mechanical response, these resonators can be cooled down to quantum ground state with direct cooling methods such as dilution fridge cooling. These type of resonators can achieve efficient conversion between electrical, optical, and mechanical signals which can be utilized for quantum information science and sensing applications in the field of nanoelectromechanical systems. / 2023-09-24T00:00:00Z

A vibration-based sound power (VBSP) measurement method is appealing because of its potential versatility in application compared to pressure- and intensity-based methods. The VBSP method is based on the well-known elementary radiators approach and is reliant on the acoustic radiation resistance matrix. Previous research has developed and validated the VBSP method for flat plates and cylinders. This thesis details work on extending the VBSP method to arbitrarily-curved structures. The approach of computing surface normal velocities from 3D velocity data measured by a scanning laser Doppler vibrometer (SLDV) is presented. This approach is validated with experimental sound power results of a cylindrical shell using the VBSP method with 3D velocity and geometry data. The sound power results are shown to have good agreement with ISO 3741 results. Experimental sound power results from three simple-curved plates using the VBSP and ISO 3741 methods are shown to have good agreement. These experimental results indicate that the VBSP method is less sensitive to background noise than the ISO 3741 method. An overview of exploring inherent symmetry in the radiation resistance matrix is presented for the purpose of increasing efficiency in applying the VBSP method. Sound power sensitivity to the formulation of the radiation resistance matrix is explored as another relevant option for increasing the efficiency of the VBSP method for many cases and for extending the method to more complex structures. The results of the radiation resistance matrix exploration enable the VBSP method to apply to arbitrarily-curved structures. Experimental sound power results using the VBSP method with the simple-curved plate radiation resistance matrix and the ISO 3741 method are compared for two arbitrarily-curved panels and are shown to have good agreement. The VBSP method based on the simple-curved plate form of the radiation resistance matrix is shown to have excellent agreement with numerical results from boundary element models, which inherently use the appropriate form of the radiation resistance matrix.

Two experiments were conducted to study the active control of acoustic radiation due to discontinuities on thin beams. One experiment investigated the radiation from a clamped end condition and the other investigated the radiation from a blocking mass. The beams were excited by subsonic flexural traveling waves which "scattered" (or produced reflected and transmitted traveling and near-field waves) when they encountered the discontinuity. This "scattering" produced supersonic wave number components in the beam vibrational response which were responsible for the acoustic radiation. The main purpose of these experiments was to control the acoustic radiation from discontinuities on beams by actively changing the characteristics of the "scattered" waves with control actuators. In each experiment the system was disturbed by a harmonic, subsonic input from a point force shaker. Control actuator( s) (in the form of shakers and piezoelectric actuators) were attached to the beam near the discontinuity. Error microphone(s) were positioned in the acoustic field which supplied an error signal to the digital controller. The digital controller employed was the filtered-x version of the adaptive LMS algorithm programmed on a dedicated signal processing board in a personal computer. An array of accelerometers was attached to the beam which were used to decompose the complex amplitudes of an assumed displacement equation. By applying a spatial Fourier transform to the displacement equation the wavenumber components present in the beam displacement were calculated. This aided in the investigation of the mechanism by which control of the acoustic field was affected. Results from these experiments showed that large attenuations at the error microphones were possible (as much as 50dB) along with global attenuation of the acoustic field. The mechanism by which the control of the acoustic far-field was achieved was demonstrated as a decrease in the supersonic wavenumber components in the beam vibrational response. / Master of Science

A double loop control scheme is developed to control broadband acoustic radiation from a cylinder. An analog feedback loop is investigated and developed to add damping to the cylinder at particular frequencies of interest. Circuitry is developed and refined to condition Polyvinylidene Fluoride Filnl (PVDF) sensor outputs as strain rate signals. The strain rate signals are used in the feedback loop to provide damping to the structure. In conjunction with the feedback loop a feedforward loop is also implemented. The feedforward loop utilizes the filtered-x LMS algorithm. The result of combining the two control laws was unknown prior to implementation.The resulting control scheme shows that the feedback control law is effective in attenuating undesirable frequency components in the feedforward error sensor. This results in an error sensor signal which is highly correlated with the disturbance. With a more correlated error signal a more effective feedforward control is achieved. The resulting control system provides acoustic control over a wide range of frequencies. The filtered-x LMS algorithm is applied to an effective acoustic radiator. The feedback loop provides for broadband control of the structure. Typical double loop controller results show power spectrum reductions of 35 dB for an effective acoustic radiator and reductions of 10 dB for other frequencies in the excitation range. In addition, the measured controlled plant transfer functions show significant reductions in the transfer of energy through the structure. Overall Sound Pressure Level (SPL) reduction in the acoustic field generated by the cylinder in response to a random excitation with a harmonic component was 4.9 dB for feedback, 18.4 dB for feedforward, and 25.2 dB for the double loop controller. / Master of Science

Die vorliegende medizinische Dissertation untersucht nicht-invasive bildgebende Verfahren wie die konventionelle Sonographie, die Acoustic radiation force impulse (ARFI)-Elastographie sowie die Transiente Elastographie (TE) zur Detektion von Komplikationen in der Frühphase nach allogener Stammzelltransplantation. Dem kurativen Therapieansatz der Stammzelltransplantation steht ein hohes Komplikationspotential gegenüber. Besonders hepatobiliär treten Graft-versus-host Erkrankungen (GvHD) sowie Gefäßkomplikationen (VOD) auf. Der bisherige diagnostische Goldstandard, die Leberbiopsie, ist als invasives Verfahren mit einer hohen Intra- und Inter-Untersucher-Variabilität sowie der geringen Repräsentativität als Screeningmethode ungeeignet. Die Elastographieverfahren ARFI und TE als nicht-invasive Alternativen ermitteln die Lebergewebesteifigkeit als Surrogatparameter fibrotischer Veränderungen und wurden bereits in zahlreichen Studien als geeignete Diagnoseverfahren für Leberfibrose und -zirrhose unterschiedlicher Ätiologie definiert. Ziel dieser prospektiven Pilotstudie war die Evaluation der genannten Methoden zur Detektion von Frühkomplikationen nach allogener Stammzelltransplantation. Die Ergebnisse der Studie zeigen, dass sowohl die konventionelle Sonographie als auch die Transiente Elastographie pathologische Organveränderungen vor allem des hepatobiliären Systems detektieren können. Allerdings erscheinen diese Veränderungen unspezifisch. Es bestehen keine signifikanten Unterschiede zwischen Patienten mit und ohne Komplikationen. Anders bei der ARFI-Elastographie. Hier zeigten die Messwerte im linken Leberlappen signifikant höhere Werte bei Patienten mit Komplikationen. Zusammenfassend ist die ARFI-Elastographie zur Prädiktion möglicher Komplikationen nach allogener Stammzelltransplantation geeignet, sollte allerdings mit anderen diagnostischen Verfahren ergänzt werden.

Recent advances and interest in ultrasound particle manipulation calls for theoretical understanding of acoustic radiation force and torque exerted on a configuration of multiple particles. In this thesis we theoretically study the acoustic radiation force and torque exerted by an arbitrary acoustic beam on a cluster of spherical particles in an inviscid fluid. The method is based on the partial-wave expansion (PWE) and the translational addition theorem for spherical wave functions. The combination of (PWE) and addition theorem Method enable us to solve the associated multiple scattering problem by numerically computing the (PWE) coefficients in a system of linear equations. On the other hand, when we consider the radiation force and torque exerted on a single sphere, the addition theorem has the advantage to solve this problem in a closed form. After obtaining the PWE coefficients, the acoustic radiation force and torque is computed through the farfield series solution. To illustrate the method, the acoustic radiation force and torque exerted on a single or multiple spheres are analyzed. In the case of a single sphere, the force is generated by a spherically focused ultrasound beam, where as the torque is generated by a Bessel vortex beam. For the multiple spheres configuration, the radiation force is induced by a traveling and a standing plane wave. In a specific configuration of three olive oil droplets suspended in water, with radii of the order of the wavelength, we found that rescattering events produce an acoustic interaction force, which significantly changes the radiation force on each droplet depending on the inter-droplet distance. In addition, we have found for the first time that an acoustic interaction torque due to the nonsymmetric spatial distribution of the acoustic energy density to the droplets. Further more, our study does not have restrictions on the spheres size compared to the wave length, nor on their composition material, which includes rigid, void, compressional liquid, elastic and viscoelastic solids, and layered material. Finally, this study has direct applications on methods for noncontact object handling by acoustic waves such as acoustic levitation, acoustical tweezers, and acoustophoresis in lab-on-a-chip devices. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Recentes avanços e interesse em manipulação de partículas necessitam de uma maior compreensão teórica da força de radiação e torque acústico exercidos sobre uma configuração de múltiplas partículas. Nesta tese, nós estudamos teoricamente a força de radiação e torque acústico exercido por um feixe acústico arbitrário em um conjunto de partículas esféricas suspensas em um fluido não viscoso. O método baseia-se na expansão de ondas parciais (EOP) e no teorema translacional da adição para funções de onda esférica. A combinação do método de ondas parciais com o teorema da adição nos permitir resolver o problema de espalhamento mútiplo computando numericamente os coeficientes da expansão em um sistema de equações lineares. Por outro lado, quando consideramos a força e torque de radiação exercidos sobe uma única esfera, o teorema da adição tem a vantagem para resolver este problema exatamente. Após a obtenção dos coeficientes, a força e o torque de radiação são calculados usando um método em séries no campo distante. Para ilustrar o método, a força e o torque exercidos sobre uma ou multiplas esferas são analisados. Para o de uma única esfera, a força de radiação é gerada por um feixe de ultrassom focalizado. Para uma configuração de multiplas esferas, a força de radiação é induzida por ondas planas e estacionarias. Numa configuração específica de três gotas de azeite suspensas em água, com raios da ordem do comprimento de onda, verificou-se que as ondas reespalhadas produzem uma força de interação acústica, o que altera significativamente a força de radiação em cada gota em função da distância inter-gota. Além disso, verificou-se, pela primeira vez que um torque de interação acústico devido a uma distribuição espacial não simétrica da densidade de energia acústica para as gotas. Além disso, nosso estudo não tem restrições quanto ao tamanho esferas em comparação com o comprimento de onda, nem sobre a sua composição, que inclui rígida, líquida, elástica e sólidos viscoelásticos. Por fim, este estudo tem aplicações diretas sobre os métodos de manipulação de objetos sem contato por ondas acústicas, tais como a levitação acústica, pinças acústicas e acoustophoresis em dispositivos lab-on-a-chip.

The study of acoustic radiation force and torque phenomena has attracted an enormous interest of the scientific community, due to applications of these phenomena in noncontact particles manipulation. In this work, we perform a theoretical analysis of acoustic radiation force and torque exerted on a homogeneous visco elastic particle in the Rayleigh scattering limit (the particle radius is much smaller than the incident wavelength) by a wave with arbitrary geometry. Our study is based on the partial-wave expansion in spherical coordinates of the incident and scattered waves. In this context, the radiation force and torque are obtained analytically in terms of an infinite series which involves the scattering and incident expansion coefficients. We assume that the particle behaves as a linear viscoelastic solid, which obeys the fractional Kelvin-Voigt model. Analytical expressions for the radiation force and torque are obtained considering the low- and high-frequency approximation in the viscoelastic model. The developed theory is used to describe the interaction of acoustic waves (traveling and standing plane waves, and zero and first-order Bessel beams) with a low-and high-density polyethylene particle. Our results show that the axial acoustic radiation force might become negative (i.e. in opposition to the wave propagation direction) when a certain condition involving the physical parameters of the particle is satisfied. Negative acoustic radiation torque due a beam of first-order Bessel may also occur when the same condition of negative radiation force is met. Remarkably, this is the first time that negative radiation force is predicted on a homogeneous particle in the Rayleigh scattering regime. Further more, the stability of the transverse acoustic radiation force generated by a Bessel beam is also investigated. We show a full 3D tractor Bessel vortex beam acting on the high-density polyethylene (HDPE). In the analysis of acoustic radiation force generated on a viscoelastic particle by a standing plane wave, relevant deviations arose in comparison with the solid elastic model for the particles. The magnitude of the radiation force and torque on a HDPE described by the viscoelastic model behaves differently (negative radiation force) compared with other materials (solid elastic and compressible fluid particle) due to traveling plane wave and Bessel beams. Finally, we believe that this study may help further enhance the development of acoustic levitation, particle handling in acoustofluids, and acoustical tweezers devices. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo dos fenômenos de força e torque de radiação acústico tem atraído um enorme interesse da comunidade científica, devido a aplicações desses fenômenos em manipulação de partículas sem contato. Neste trabalho, realizamos uma análise teórica da força e torque de radiação acústico exercido sobre uma partícula visco elástica homogênea no limite do espalhamento de Rayleigh (o raio da partícula é muito menor que o comprimento de onda incidente) por uma onda com geometria arbitrária. Nosso estudo baseia-se na expansão de ondas parciais em coordenadas esféricas das ondas incidente e espalhada. Nesse contexto, a força e o torque de radiação são obtidos analiticamente em termos de uma série infinita que envolve os coeficientes de expansão das ondas espalhada e incidente. Assumimos que a partícula se comporta como um sólido viscoelástico linear, que obedece o modelo de Kelvin-Voigt fracionário. Fórmulas analíticas para a força e torque de radiação são obtidas considerando uma aproximação de baixa e de alta frequência no modelo viscoelástico. A teoria desenvolvida é usada para descrever a interação de ondas acústicas (onda plana progressiva, onda plana estacionária, feixes de Bessel de ordem zero e de primeira ordem) com partículas de polietileno de baixa e de alta densidade. Os nossos resultados mostram que a força de radiação acústica axial pode ser negativa (isto é, em oposição à direção de propagação da onda) quando uma determinada condição envolvendo os parâmetros físicos da partícula é satisfeita. Torque de radiação acústico negativo devido a um feixe de Bessel de primeira ordem também pode ocorrer quando a mesma condição da força de radiação negativa for atendida. Notavelmente, esta é a primeira vez que a força de radiação negativa é prevista sobre uma partícula homogênea no regime de espalhamento Rayleigh. Além disso, a estabilidade transversal da força de radiação acústica gerada pelo feixe de Bessel também é investigada. Mostramos que um feixe de Bessel trator 3D completo atua sobre uma partícula de polietileno de alta densidade (PEAD). Na análise da força de radiação acústica gerada sobre uma partícula viscoelástica por uma onda plana estacionária, desvios relevantes surgiram em comparação com partícula sólida elástica. A amplitude da força e torque de radiação sobre uma PEAD descrita pelo modelo viscoelástico apresenta um comportamento diferente (força de radiação negativa) comparados com os outros materiais (sólida elástica e fluida com absorção longitudinal) devido a onda plana progressiva e feixes de Bessel. Por fim, acreditamos que este estudo pode ajudar a melhorar ainda mais o desenvolvimento de dispositivos de levitação acústica, manipulação de partículas em acustofluídica e pinças acústicas.

<p>Implemented on an intracardiac echocardiography transducer, acoustic radiation force methods may provide a useful means of characterizing the heart's elastic properties. Elasticity imaging may be of benefit for diagnosis and characterization of infarction and heart failure, as well as for guidance of ablation therapy for the treatment of arrhythmias. This thesis tests the hypothesis that with appropriately designed imaging sequences, intracardiac acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) are viable tools for quantification of myocardial elasticity, both temporally and spatially. Multiple track location SWEI (MTL-SWEI) is used to show that, in healthy in vivo porcine ventricles, shear wave speeds follow the elasticity changes with contraction and relaxation of the myocardium, varying between 0.9 and 2.2 m/s in diastole and 2.6 and 5.1 m/s in systole. Infarcted tissue is less contractile following infarction, though not unilaterally stiffer. Single-track-location SWEI (STL-SWEI) is proven to provide suppression of speckle noise and enable improved resolution of structures smaller than 2 mm in diameter compared to ARFI and MTL-SWEI. Contrast to noise ratio and lateral edge resolution are shown to vary with selection of time step for ARFI and arrival time regression filter size for STL-SWEI and MTL-SWEI. </p><p>In 1.5 mm targets, STL-SWEI achieves alternately the tightest resolution (0.3 mm at CNR = 3.5 for a 0.17 mm filter) and highest CNR (8.5 with edge width = 0.7 mm for a 0.66 mm filter) of the modalities, followed by ARFI and then MTL-SWEI.</p><p>In larger, 6 mm targets, the CNR-resolution tradeoff curves for ARFI and STL-SWEI overlap for ARFI time steps up to 0.5 ms and kernels $\leq$1 mm for STL-SWEI. STL-SWEI can operate either with a 25 dB improvement over MTL-SWEI in CNR at the same resolution, or with edge widths 5$\times$ as narrow at equivalent CNR values, depending on the selection of regression filter size. Ex vivo ablations are used to demonstrate that ARFI, STL-SWEI and MTL-SWEI each resolve ablation lesions between 0.5 and 1 cm in diameter and gaps between lesions smaller than 5 mm in 3-D scans. Differences in contrast, noise, and resolution between the modalities are discussed. All three modalities are also shown to resolve ``x''-shaped ablations up to 22 mm in depth with good visual fidelity and correspondence to surface photographs, with STL-SWEI providing the highest quality images. Series of each type of image, registered using 3-D data from an electroanatomical mapping system, are used to build volumes that show ablations in in vivo canine atria. In vivo images are shown to be subject to increased noise due to tissue and transducer motion, and the challenges facing the proposed system are discussed. Ultimately, intracardiac acoustic radiation force methods are demonstrated to be promising tools for characterizing dynamic myocardial elasticity and imaging radiofrequency ablation lesions.</p> / Dissertation