Changes In Acoustic Properties Research Articles

Acoustic emission for monitoring of fatigue damage in concrete elements of wind turbine towers

Wind energy has become an important player in the energy transition in Germany. Towers of onshore wind turbines are often designed as hybrid structures: the lower part is made of prestressed concrete whereas the upper part is made of steel tubes. The tall structures are permanently subjected to dynamic loads. A research project of BAM as part of the joint project WinConFat-Structure focusses on the development of techniques to monitor fatigue damage evolution in the concrete part. Results of a previous project show that a combination of ultrasonic and acoustic emission testing can give an indication for critical conditions near the end of the fatigue life of the concrete. In the ongoing project acoustic emission sensors have been installed at the base and at the transition piece between concrete and steel of a hybrid wind turbine tower. Beside of acoustic emission measurement the sensor spacing allows for measuring the concrete ultrasonic velocity along the circumference in both levels. Additional measurements like strain, temperature, inclination, or acceleration allow for comparison of environmental loads and change of acoustic properties of the concrete. The paper focusses on first acoustic measurements recorded since December 2023 in comparison to operating data of the wind turbine.

Experimental Study of the Dynamics of Lean Premixed Hydrogen Flames in a Multi Jet Combustor

Abstract In this study, the flame dynamics of lean premixed hydrogen jet flames are experimentally investigated. Acoustic and optical measurements are used to capture the response of a bundle of jet flames to acoustic forcing. Using helium as a fuel surrogate, we simulate the change in acoustic properties in the burner during the determination of cold burner transfer matrix measurements. We investigate the influence of the equivalence ratio and the addition of methane as well as the interaction of the individual flames to evaluate the scalability of the results to systems with more flames. It is shown that the changes in the dynamic flame response can primarily be explained by the flame length, which changes both with the methane share and with the equivalence ratio. It can be observed that with small changes in the equivalence ratio, the flame length and the flame transfer function (FTF) change in the same way as with a small change in gas composition. To assess the scalability of these results, we deactivate some of the jet flames and analyze how the overall response to acoustic forcing changes. We find that the FTF phase is not affected by the number of active flames. Analyzing the respective gain values, significantly stronger responses are measured for a few flames, but only small difference can be measured above a certain number of neighboring flames so that the lab scale results can also be expected to be valid for industrial configurations with a high number of flames.

Pine wood extraction by fermentation to improve its acoustical efficiency

Wood is a main material in the construction of musical instruments and speaker boxes, especially in developed countries. This study investigated the changes in acoustic properties of pine wood during the processes of fermentation, water washing, and organic washing solvent. The results indicated that both methods of water washing and ethanol-acetone mixture washing of the samples improved the values of density, modulus of elasticity, elastic stiffness, acoustic coefficient, vibration damping, and acoustic conversion efficiency. The effect of ethanol-acetone mixture washing was greater than water washing the samples. Additionally, results revealed that pretreatment before ethanol-acetone mixture washing had the most effect on vibration damping and acoustic conversion efficiency values. In general, the values obtained from ethanol-acetone mixture washing resulted in more improvement in acoustic properties compared to water washing, but the results showed that the pretreatment before water washing had a greater effect on the values of density, modulus of elasticity, elastic stiffness, and acoustic coefficient.

Brillouin Scattering Study of Electro-Optic KTa1-xNbxO3 Crystals.

The functionality enhancement of ferroelectrics by local polar clusters called polar nanoregions (PNRs) is one of the current interests in materials science. KTa1-xNbxO3 (KTN) with perovskite structure is a well-known electro-optic crystal with a large Kerr effect. The existence of PNRs in relaxor-like ferroelectric Nb-rich KTN with homovalent B-site cations is controversial. This paper reviews recent progress in understanding precursor dynamics in Nb-rich KTN crystals studied using Brillouin scattering. The intense central peak (CP) and significant softening of sound velocity are observed above the Curie temperature (TC) due to the polarization fluctuations in PNRs. The effects of Li-doping, defects, and electric fields on the growth and/or creation of PNRs are found using changes in acoustic properties. The electric-field-induced TC, which is shifted to higher values with increases in applied voltage, including critical endpoint (CEP) and field gradient by trapped electrons, are discussed as well. This new knowledge may give new insight into advanced functionality in perovskite ferroelectrics.

Sonification of weather data as a non-human-centric artistic approach

Background - In the mid-20th century, the emergence of sound studies demonstrated a shift of research interest in sonic practitioners. This field gains its prevalence by expanding the boundaries of prevailing conception through proposing alternative creative approaches in sound art practices. Methods – Two methods were presented – listening and sounding to promote creative sound making. The first method, listening involves soundwalking and recording sound from the external environments. These recordings were then re-evaluated and post-processed in audio editing software. The second method, sounding involves the creation of a weather data sonification system in Pure Data environment, in which the perceptual experience from the first method was taken into consideration. Result – First method enables the genesis of creative idiosyncrasies, such as preferences and ideas through the sonic perception of environmental events. In this process, noise and weather were identified as environmental components that share similar sensible qualities. Thus, noise is a prevalent medium that inspires the creation of sound generators in the sonification system presented in this paper. The sonic output of data sonification reveals an analogical connection between weather data and sonic parameters, in which changes in data values result in changes in acoustic properties. These outputs deliver different sensibilities based on their data parameters; sonification of temperature data might suggest an alarming effect to the listener. Conclusion – The proposed methods were intricately linked, suggesting environmental events to be perceived and realized through a non-scientific perspective. By highlighting aesthetic possibilities of environmental components, this paper presents an alternative perspective in contrast with the human-centric worldview through the creation of sonic works.

Effect of Subsurface Mediterranean Water Eddies on Sound Propagation Using ROMS Output and the Bellhop Model

Ocean processes can locally modify the upper ocean density structure, leading to an attenuation or a deflection of sound signals. Among these phenomena, eddies cause significant changes in acoustic properties of the ocean; this suggests a possible characterization of eddies via acoustics. Here, we investigate the propagation of sound signals in the Northeastern Atlantic Ocean in the presence of eddies of Mediterranean Water (Meddies). Relying on a high-resolution simulation of the Atlantic Ocean in which Meddies were identified and using the Bellhop acoustic model, we investigated the differences in sound propagation in the presence and absence of Meddies. Meddies create sound channels in which the signals travel with large acoustic energy. The transmission loss decreases to 80 or 90 dB; more signals reach the synthetic receivers. Outside of these channels, the sound signals are deflected from their normal paths. Using receivers at different locations, the acoustic impact of different Meddies, or of the same Meddy at different stages of its life, are characterized in terms of angular distributions of times of arrivals and of energy at reception. Determining the influence of Meddies on acoustic wave characteristics at reception is the first step to inverting the acoustic signals received and retrieving the Meddy hydrological characteristics.

Lesion location and lesion creation affect outcomes after focused ultrasound thalamotomy.

MRI-guided focused ultrasound thalamotomy has been shown to be an effective treatment for medication refractory essential tremor. Here, we report a clinical-radiological analysis of 123 cases of MRI-guided focused ultrasound thalamotomy, and explore the relationships between treatment parameters, lesion characteristics and outcomes. All patients undergoing focused ultrasound thalamotomy by a single surgeon were included. The procedure was performed as previously described, and patients were followed for up to 1 year. MRI was performed 24 h post-treatment, and lesion locations and volumes were calculated. We retrospectively evaluated 118 essential tremor patients and five tremor-dominant Parkinson's disease patients who underwent thalamotomy. At 24 h post-procedure, tremor abated completely in the treated hand in 81 essential tremor patients. Imbalance, sensory disturbances and dysarthria were the most frequent acute adverse events. Patients with any adverse event had significantly larger lesions, while inferolateral lesion margins were associated with a higher incidence of motor-related adverse events. Twenty-three lesions were identified with irregular tails, often extending into the internal capsule; 22 of these patients experienced at least one adverse event. Treatment parameters and lesion characteristics changed with increasing surgeon experience. In later cases, treatments used higher maximum power (normalized to skull density ratio), accelerated more quickly to high power, and delivered energy over fewer sonications. Larger lesions were correlated with a rapid rise in both power delivery and temperature, while increased oedema was associated with rapid rise in temperature and the maximum power delivered. Total energy and total power did not significantly affect lesion size. A support vector regression was trained to predict lesion size and confirmed the most valuable predictors of increased lesion size as higher maximum power, rapid rise to high-power delivery, and rapid rise to high tissue temperatures. These findings may relate to a decrease in the energy efficiency of the treatment, potentially due to changes in acoustic properties of skull and tissue at higher powers and temperatures. We report the largest single surgeon series of focused ultrasound thalamotomy to date, demonstrating tremor relief and adverse events consistent with reported literature. Lesion location and volume impacted adverse events, and an irregular lesion tail was strongly associated with adverse events. High-power delivery early in the treatment course, rapid temperature rise, and maximum power were dominant predictors of lesion volume, while total power, total energy, maximum energy and maximum temperature did not improve prediction of lesion volume. These findings have critical implications for treatment planning in future patients.

Monitoring of Pickering emulsion stability during magnetic heating using ultrasound measurements

Magnetic heating of colloidal systems is becoming a more and more common route for inducing temperature rise, especially in applications where very local temperature elevation is desired. Although the calorimetric properties of magnetic colloids are extensively investigated, the influence of the alternating magnetic field on their structure has rarely been reported. Meanwhile, potential permanent structural changes such as the formation of agglomerates can affect the stability of magnetic dispersions or magnetic Pickering emulsions. In the present work, we propose to use ultrasound as a technique to determine if such changes occur during magnetic heating. Oil-in-oil emulsions with magnetite particle shells around the droplets and oil-based magnetic fluids were exposed to alternating magnetic fields, and the changes in ultrasonic attenuation and the speed of ultrasound were determined. Finally, changes in acoustic properties were investigated in dispersions of magnetic and polystyrene particles after heating to the melting temperature of the soft particles.

Thermal resistance at a twist boundary and a semicoherent heterointerface

Traditional models of interfacial phonon scattering, including the acoustic mismatch model (AMM) and diffuse mismatch model (DMM), take into account the bulk properties of the material surrounding the interface, but not the atomic structure and properties of the interface itself. Here, we derive a theoretical formalism for the phonon scattering at a dislocation grid, or two interpenetrating orthogonal arrays of dislocations, as this is the most stable structure of both the symmetric twist boundary and semicoherent heterointerface. With this approach, we are able to separately examine the contribution to thermal resistance due to the step function change in acoustic properties and due to interfacial dislocation strain fields, which induces diffractive scattering. Both low-angle Si-Si twist boundaries and the Si-Ge heterointerfaces are considered here and compared to previous experimental and simulation results. This work indicates that scattering from misfit dislocation strain fields doubles the thermal boundary resistance of Si-Ge heterointerfaces compared to scattering due to acoustic mismatch alone. Scattering from grain boundary dislocation strain fields is predicted to dominate the thermal boundary resistance of Si-Si twist boundaries. This physical treatment can guide the thermal design of devices by quantifying the relative importance of interfacial strain fields, which can be engineered via fabrication and processing methods, versus acoustic mismatch, which is fixed for a given interface. Additionally, this approach captures experimental and simulation trends such as the dependence of thermal boundary resistance on the grain boundary angle and interfacial strain energy.

Basic principles for building seismic monitoring systems in rockburst-hazardous coal seam mining

The main directions of development of seismic monitoring systems in underground mineral mining are analyzed. The expediency of passive registration of natural seismic activity is proved, which provides prediction of geodynamic phenomena by locating the centers of seismic events and determining their energy level. The methods of active seismic monitoring (seismic tomography, cross-borehole survey, recording of seismic signal from a rock-breaking tool) are technically more difficult to implement. The promising methods for processing seismic information are geolocation, neural network technology, cluster analysis, and integration with numerical stress–strain analysis of and changes in acoustic properties of rock mass. The configuration of the platform developed at VNIMI and the GITS seismic monitoring system, which includes from 6 to 12 three-component seismic sensors installed permanently in wells or on pedestals, is described. The detailed layouts of seismic sensors at recording points and in gateways in extraction panels are presented. The main technical characteristics of GITS are given: the signal frequency range is 0.1–1000 Hz, the minimum recorded signal level is 0.01 mV. The main test data of GITS in Komsomolskaya mine of Vorkutaugol are described: the average annual levels of seismic activity and energy of seismic events are found to be relatively stable; the relationship between seismic event with the maximum total energy and the alternating increment in the relative criterion is defined, and the local increase in the average energy of a single event in time from the moment the main roof caving is identified. Aimed to substantiate the regional and local prediction criteria of probability of geodynamic events caused by confining pressure, VNIMI implements integrated research in mines in different regions.

Acoustical longevity and durability of pavements

The tire-pavement interface has been shown to be the primary source of traffic noise when vehicles travel faster than about 30 mph (48 kph). Consequently, application of quieter pavement results in lower noise levels for drivers and for those living and working near a roadway. There is some hesitation by US regulatory agencies over using quieter pavement surfaces as noise mitigation on highways due to concern over changes in acoustical properties over time. To address this concern, long-term pavement research has been conducted within four robust studies in California and Arizona, comprising a total of seven flexible and six rigid pavement surfaces. Acoustical performance of these surfaces was measured several times per year over periods of 10 to 16 years. In addition to the four primary long-term pavement studies, several smaller studies have included repeat measurements of pavements over time. This article summarizes and compares the results of the four long-term pavement studies and the smaller repeat measurement studies.

Look Ahead of the Bit While Drilling: Potential Impacts and Challenges of Acoustic Seismic While Drilling in the McMurray Formation

SummaryThe oil and gas industry, operating and service companies, and academia are actively searching for ways to look ahead of the drill bit while drilling to reduce the risks and costs of the operation and improve the well-placement process. Optimal drilling in challenging and highly heterogeneous reservoirs, where geological data cannot adequately constrain high-frequency variations in rock properties, requires reliable subsurface information from around and ahead of the drill bit. To provide this, we have developed a seismic-while-drilling (SWD) imaging algorithm using signal processing, drillstring modeling, and prestack wave-equation migration.To extend the visibility ahead of the bit, we use the drill bit as a seismic source and image the changes in acoustic properties of rocks both around and ahead of the drill bit. The common practice is to build reverse vertical seismic profile (R-VSP) gathers. Here, we use a blind deconvolution algorithm to estimate the drill-bit source signature from the data directly. Alternatively, we can estimate such a signature through drillstring modeling and surface measurements (i.e., hookload and hook speed). The drillstring dynamics are modeled and analyzed using Riemann's invariants and a backstepping approach in a field-verified model. Next, we enter the estimated source signature into the prestack wave-equation depth-imaging workflow. Our simulations show that providing the drill-bit source signature to the prestack wave-equation depth migration consistently delivers reliable subsurface images around and ahead of the drill bit.The output of our workflow is a high-resolution subsurface image, which is then applied to provide vital information in oil-sands reservoirs for placement of steam-assisted-gravity-drainage (SAGD) well pairs. Compared with conventional practices, the proposed methodology images around and ahead of the drill bit enable interactive decision making and optimal well placement. The key feature of the presented methodology is that instead of cross correlating the SWD data with the pilot trace and building R-VSP gathers, we use the estimated drill-bit source signature and deliver high-resolution prestack depth-migrated images.Through numerical modeling, we tested the potential impacts, validity, and challenges of the proposed methodology in drilling horizontal wells in SAGD settings with an emphasis on the McMurray Formation. We further compared the results with the conventional drilling practice. In contrast to existing tools that have limited depth of penetration, interpreting SWD data in real time confidently maps key target features ahead of the drill bit. This imaging workflow provides sufficient time to precisely control the borehole trajectory and stay within the desired reservoir zone. Accordingly, it mitigates the risk of intersecting mudstone-filled channels and lean zones.

A Review of Ultrasound Thermometry Techniques

Acoustic thermometry is one of non-invasive methods to measure the temperature inside tissue area. Especially, when using the thermal therapy techniques such as High Intensity Focused Ultrasound (HIFU) and other thermal based methods, thermal assessment of heated area seems to be necessary. Some of acoustic properties of medium are temperature dependent; therefore, evaluation of temperature dependent parameters will be an indirect and non-invasive approach in thermometry. In this paper some of thermometry methods based on changes in acoustic properties of medium have been reviewed. The published methods are classified in two main categories: passive and active thermometry. In the passive thermometry, the thermal measurement probes, induced no acoustic signals to the medium, but they receive the radiated signals from the heated medium. In active method, the thermometry probe transmits a signal into the heated region and receives the echoes, then the received RF signals are processed in order to measure the temperature.

Ultrasonic Hydrogel Biochemical Sensor System.

In this work, we present a proof-of-concept hydrogel-based sensor system capable of wireless biochemical sensing through measuring backscattered ultrasound. The system consists of silica-nanoparticle embedded hydrogel deposited on a thin glass substrate, presenting two interfaces for backscattering (tissue/hydrogel and hydrogel/glass), which allows for system output to be invariant under the change in acoustic properties (e.g. attenuation, reflection) of the intervening biological tissue. We characterize the effect of silica nanoparticles (acoustic contrast agents) loading on the hydrogel's swelling ratio and its ultrasonic backscattering properties. We demonstrate a wireless pH measurement using dual modes of interrogations, reflection ratio and time delay. The ultrasonic hydrogel pH sensor is demonstrated with a sensing resolution of 0.2 pH level change with a wireless sensing distance around 10 cm.

Experimental Investigation of the Creep Behaviour of Coal by Monitoring Changes of Acoustic Properties

Time-dependent deformation of coal is a major concern for deep coal mining. When experiencing high stress conditions, the enhanced time-dependent deformation of coal will become a very possible factor to trigger the violent failure of underground openings. For this study, the inner structural variation of an extremely inhomogeneous coal subjected to incremental creep stress has been experimentally investigated by monitoring both the macroscopic deformation and acoustic property. Results show the following: (1) The pronounced inhomogeneity of coal induces considerable irregularities in creep strain data collected during the increase of stress level. These flawed data highlight the shortcomings of conventional strain-time relationship experiments for deciphering the mechanisms that control creep; (2) The mechanical response of samples under creep compression is the result of competition between compaction and cracking. Cracking deteriorates the structure and increases the ultrasonic attenuation, whilst the compaction causes the densification along the axial axis and reduces attenuation; (3) Long-term creep involves multiple structural deformations that alter the internal structure of the coal. This results in fluctuations of the ultrasonic velocities and their dynamic moduli; (4) During uploading phase of short term creep, vertical cracks develop and transform the sample into a structure consisting of separated columns. Further deterioration of the coal increases the possibility of tensile and shear failure of individual columns, which can trigger the violent collapse of an already fragile structure.

Relating functional diversity of infauna and sediment geoacoustic properties

Marine sediments cover most of the seafloor and vary in physical structure from unconsolidated gravel or sand grains to cohesive, gel-like muds. Sediments also provide a habitat to diverse and abundant animals (infauna). Infauna are impacted by but can also affect the sediment’s physical and biogeochemical properties and fluid flow through and across the sediment. Through activities such as burrowing, feeding, and construction of tubes and rigid body parts, many infauna act as ecosystem engineers, directly and indirectly creating and changing their habitats. Characterization of infauna using functional groups based on how their activities affect their sediment environments can simplify the broad diversity of infauna. For example, some infauna create habitat structure in addition to modifying surface topography through tube construction. Others change sediment properties through bioturbation (animal-induced particle mixing) and bioirrigation (fluid mixing) as they burrow. Structure creation and bioturbation/irrigation can affect sediment geotechnical properties such as porosity, bulk density, grain size heterogeneity, fracture toughness, and stiffness. Changes in these properties can influence acoustic wave speed, attenuation, and backscatter. Thus, acoustics tools can be used to observe and quantify animal-sediment interactions relatively noninvasively by relating the activities of different functional groups with changes in acoustic properties of sediments.

Diffraction imaging for seal evaluation using ultra high resolution 3D seismic data

Cap rock is any impermeable or low permeability formation that may trap oil, gas or water, preventing it from migrating to the surface. Evaluation of sealing properties of the cap rock is a critical task for seismic exploration. It is important for oil and gas prospecting as well as for locating reservoirs appropriate for carbon dioxide storage. The latter has been proposed as one solution to global climate change caused by heat-trapping anthropogenic gasses in the atmosphere. A fluid escaped from the reservoir fills voids in the overlying strata thereby causing local changes of acoustic properties. We aim to explore such fluid-saturated areas and thus evaluate sealing properties of underlying cap rocks. We assume that local acoustic impedance changes caused by fluid migration generate seismic diffractions. We isolate diffracted waves from P-Cable seismic data acquired over the area of interest and perform diffraction analysis of the near-surface interval (above 200 m).In the diffraction image obtained, we interpret an extensive system of broad sinuous channels, narrow linear faults, and diffuse fracture networks. In addition, we detect high-diffractivity anomalies, which extend vertically and laterally. We note no evidence of these anomalies in a conventional seismic image and associated seismic attribute (similarity and fracture density) volumes. We associate this high diffractivity to a variable pore fluid composition and saturation, which we infer to be due to hydrocarbon migration from the underlying strata. Consequently, we conclude poor seal quality for the underlying cap rocks.During data processing, we test diffraction focusing analysis for velocity model building. This option appears quite valuable for P-Cable data processing because of short offset and limitations of the standard velocity analysis.

High-pass filtering obscures stimulus encoding characteristics of the auditory brainstem response: Evidence from click and tone stimuli

The auditory brainstem response (ABR) is an electrophysiological measure of early auditory processing. While previous work has examined ABRs to clicks, tones, speech, and music, it remains unclear how changes in acoustic properties (e.g., frequency) map onto specific changes in ABR components. This may be partly due to filtering during data processing. High-pass filtering can severely distort cortical and subcortical responses, potentially obfuscating how stimuli are encoded. To address this, we measured ABRs to a wide range of pure tones (250 to 8000 Hz) and examined how high-pass filtering affects tone- and click-evoked ABRs. In Experiment 1, various high-pass filter settings (0.1-300 Hz) were applied to click-evoked ABRs. In Experiment 2, ABRs to brief tones across a six-step frequency continuum were collected, and the same high-pass filter settings were applied. Results indicate that excessive high-pass filtering diminishes the amplitude of ABR components, consistent with previous findings. In addition, filtering can obscure true effects of stimulus frequency. With appropriate filters, we find that the amplitude of wave V tracks stimulus frequency log-linearly, demonstrating that tonotopic organization is preserved and easily detectable early in processing. Future ABR work should minimize the use of high-pass filters when studying the encoding of acoustic information.

Tool-use-associated sound in the evolution of language.

Proponents of the motor theory of language evolution have primarily focused on the visual domain and communication through observation of movements. In the present paper, it is hypothesized that the production and perception of sound, particularly of incidental sound of locomotion (ISOL) and tool-use sound (TUS), also contributed. Human bipedalism resulted in rhythmic and more predictable ISOL. It has been proposed that this stimulated the evolution of musical abilities, auditory working memory, and abilities to produce complex vocalizations and to mimic natural sounds. Since the human brain proficiently extracts information about objects and events from the sounds they produce, TUS, and mimicry of TUS, might have achieved an iconic function. The prevalence of sound symbolism in many extant languages supports this idea. Self-produced TUS activates multimodal brain processing (motor neurons, hearing, proprioception, touch, vision), and TUS stimulates primate audiovisual mirror neurons, which is likely to stimulate the development of association chains. Tool use and auditory gestures involve motor processing of the forelimbs, which is associated with the evolution of vertebrate vocal communication. The production, perception, and mimicry of TUS may have resulted in a limited number of vocalizations or protowords that were associated with tool use. A new way to communicate about tools, especially when out of sight, would have had selective advantage. A gradual change in acoustic properties and/or meaning could have resulted in arbitrariness and an expanded repertoire of words. Humans have been increasingly exposed to TUS over millions of years, coinciding with the period during which spoken language evolved. ISOL and tool-use-related sound are worth further exploration.

Accounting for multicompetence and restructuring in the study of speech

Phonetic studies meant to generalize to monolingual speakers of a target language have often examined individuals with considerable experience using another language, such as the immigrant native speaker. This paper presents, first, results from a meta-analysis of the literature, suggesting that conflation of ostensibly bilingual (“multicompetent”) individuals with monolinguals remains common practice and, second, longitudinal data on speech production that demonstrate why this practice is problematic. Adult native English speakers recently arrived in Korea showed significant changes in acoustic properties of their English production during their first weeks of learning Korean (“phonetic drift”) and, furthermore, continued to show altered English production a year later, months after their last Korean class and without extensive use of Korean in daily life. These patterns suggest that the linguistic experience associated with residence in a foreign language environment tends to induce and then prolong phonetic drift of the native language, making the multicompetent native speaker living in a foreign language environment unrepresentative of a monolingual in the native language environment. The speed and persistence of these effects highlight the need for language researchers to be explicit about the population under study and to accordingly control (and describe) language background in a study sample.