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In recent decades, economic crises and political reforms focused on employment flexibilization have increased the use of non-standard employment (NSE). National political and economic contexts determine how employers interact with labour and how the state interacts with labour markets and manages social welfare policies. These factors influence the prevalence of NSE and the level of employment insecurity it creates, but the extent to which a country’s policy context mitigates the health influences of NSE is unclear. This study describes how workers experience insecurities created by NSE, and how this influences their health and well-being, in countries with different welfare states: Belgium, Canada, Chile, Spain, Sweden, and the United States. Interviews with 250 workers in NSE were analysed using a multiple-case study approach. Workers in all countries experienced multiple insecurities (e.g., income and employment insecurity) and relational tension with employers/clients, with negative health and well-being influences, in ways that were shaped by social inequalities (e.g., related to family support or immigration status). Welfare state differences were reflected in the level of workers’ exclusion from social protections, the time scale of their insecurity (threatening daily survival or longer-term life planning), and their ability to derive a sense of control from NSE. Workers in Belgium, Sweden, and Spain, countries with more generous welfare states, navigated these insecurities with greater success and with less influence on health and well-being. Findings contribute to our understanding of the health and well-being influences of NSE across different welfare regimes and suggest the need in all six countries for stronger state responses to NSE. Increased investment in universal and more equal rights and benefits in NSE could reduce the widening gap between standard and NSE.

There is growing evidence that consumption of ultra-processed food (UPF) has become a leading cause of global premature deaths and preventable diet-related diseases. To reduce consumption of UPF requires an understanding of the multiple forces behind it, including the understudied question of what makes UPF appealing. This critical scan of literature across multiple disciplines aims to fill this gap. We conclude that appeal is a multi-dimensional construct generated through the interplay of the products themselves, the people consuming them, and the practices of the corporations that manufacture, market, and distribute them. We argue that these relationships need to be unpacked to understand UPF appeal fully, and that public health interventions must take on the multiple dimensions of UPF appeal in an integrated way to effectively reduce its consumption. We propose a conceptual framework that can guide research to analyze the causes and consequences of UPF appeal and inform the development of policies and other interventions to reduce UPF appeal and consumption.

Workers engaged in reproductive labor—the caring work that maintains society and supports its growth—contribute to societal health while also enduring the harms of precarious labor and substantial work stress. How can we conceptualize the effects of reproductive labor on workers and society simultaneously? In this commentary, we analyze four types of more relational and less relational careworkers—homeless shelter workers, school food workers, home care aides, and household cleaners—during the COVID-19 pandemic. We then make a case for a new model of societal health that recognizes the contributions of careworkers and healthy carework. Our model includes multi-sectoral social policies supporting both worker health and societal health and acknowledges several dimensions of work stress for careworkers that have received insufficient attention. Ultimately, we argue that the effects of reproductive labor on workers and society must be considered jointly, a recognition that offers an urgent vision for repairing and advancing societal health.

The COVID-19 crisis is a global event that has created and amplified social inequalities, including an already existing and steadily increasing problem of employment and income insecurity and erosion of workplace rights, affecting workers globally. The aim of this exploratory study was to review employment-related determinants of health and health protection during the pandemic, or more specifically, to examine several links between non-standard employment, unemployment, economic, health, and safety outcomes during the COVID-19 pandemic in Sweden, Belgium, Spain, Canada, the United States, and Chile, based on an online survey conducted from November 2020 to June 2021. The study focused on both non-standard workers and unemployed workers and examined worker outcomes in the context of current type and duration of employment arrangements, as well as employment transitions triggered by the COVID-19 crisis. The results suggest that COVID-19-related changes in non-standard worker employment arrangements, or unemployment, are related to changes in work hours, income, and benefits, as well as the self-reported prevalence of suffering from severe to extreme anxiety or depression. The results also suggest a link between worker type, duration of employment arrangements, or unemployment, and the ability to cover regular expenses during the pandemic. Additionally, the findings indicate that the type and duration of employment arrangements are related to the provision of personal protective equipment or other COVID-19 protection measures. This study provides additional evidence that workers in non-standard employment and the unemployed have experienced numerous and complex adverse effects of the pandemic and require additional protection through tailored pandemic responses and recovery strategies.

The COVID-19 crisis is a global event that has created and amplified social inequalities, including an already existing and steadily increasing problem of employment and income insecurity and erosion of workplace rights, affecting workers globally. The aim of this exploratory study was to review employment-related determinants of health and health protection during the pandemic, or more specifically, to examine several links between non-standard employment, unemployment, economic, health, and safety outcomes during the COVID-19 pandemic in Sweden, Belgium, Spain, Canada, the United States, and Chile, based on an online survey conducted from November 2020 to June 2021. The study focused on both non-standard workers and unemployed workers and examined worker outcomes in the context of current type and duration of employment arrangements, as well as employment transitions triggered by the COVID-19 crisis. The results suggest that COVID-19-related changes in non-standard worker employment arrangements, or unemployment, are related to changes in work hours, income, and benefits, as well as the self-reported prevalence of suffering from severe to extreme anxiety or depression. The results also suggest a link between worker type, duration of employment arrangements, or unemployment, and the ability to cover regular expenses during the pandemic. Additionally, the findings indicate that the type and duration of employment arrangements are related to the provision of personal protective equipment or other COVID-19 protection measures. This study provides additional evidence that workers in non-standard employment and the unemployed have experienced numerous and complex adverse effects of the pandemic and require additional protection through tailored pandemic responses and recovery strategies.

The prevalence of precarious employment has increased in recent decades and aspects such as employment insecurity and income inadequacy have intensified during the COVID-19 pandemic. The purpose of this systematic review was to identify, appraise, and synthesise existing evidence pertaining to implemented initiatives addressing precarious employment that have evaluated and reported health and well-being outcomes. We used the PRISMA framework to guide this review and identified 11 relevant initiatives through searches in PubMed, Scopus, Web of Science, and three sources of grey literature. We found very few evaluated interventions addressing precarious employment and its impact on the health and well-being of workers globally. Ten out of 11 initiatives were not purposefully designed to address precarious employment in general, nor specific dimensions of it. Seven out of 11 initiatives evaluated outcomes related to the occupational health and safety of precariously employed workers and six out of 11 evaluated worker health and well-being outcomes. Most initiatives showed the potential to improve the health of workers, although the evaluation component was often described with less detail than the initiative itself. Given the heterogeneity of the 11 initiatives regarding study design, sample size, implementation, evaluation, economic and political contexts, and target population, we found insufficient evidence to compare outcomes across types of initiatives, generalize findings, or make specific recommendations for the adoption of initiatives.

Lanthanides are present everywhere on the earth’s crust with relatively wide concentration ranges and a toxicity considered low. Gadolinium (Gd) is one of the most widespread; it is used in technological devices and in contrast media for diagnostic imaging. Its concentration in the rivers of industrialized, densely populated areas is often anomalous; in Germany, for example, it is up to three orders of magnitude higher than the expected natural values1. Many aquatic organisms are vulnerable to lanthanides2. Few studies have analyzed their potential long-term effects infreshwater. We used Xenopus laevis as a model system and the FETAX assay3,4, the expression of genes involved in early embryonic development and the ROS production to evaluate the possible toxic effects of Gd. We also verified whether it could activatethe multixenobiotic resistance mechanisms (MXMR) and induce an immune response. The embryos were exposed to Gd ions ranging from 0.2μg/L to 80μg/L considering the environmental concentrations. The FETAX assay showed that Gd is not lethal to Xenopus embryos; between 40 and 80μg/L, the treated embryos reach longer lengths than the controls and at 40μg/L 15% are malformed. As concentration increases, embryos show tachycardia and total ROS production increases. Finally, Gd modifies the expression of early embryonic genes, stimulates the production of cytokines at highest concentrations and activates the MXMR pump at the lowest. These data indicate that Gd, although not lethal for embryos, modifies their growth and exerts a slight toxic/teratogenic effect; it also induces tachycardia and activates the immune response. The observed phenotypic modifications are ascribable to modifications in the expression of genes responsible for the “construction” of the tadpole. This may be due to the production of ROS, which is known to affect gene expression, but also to the difficulty of embryos to activate MXMR. However, the most interesting results are visible at the highest concentrations used.

Algorithms are increasingly used instead of humans to perform core management functions, yet public health research on the implications of this phenomenon for worker health and well-being has not kept pace with these changing work arrangements. Algorithmic management has the potential to influence several dimensions of job quality with known links to worker health, including workload, income security, task significance, schedule stability, socioemotional rewards, interpersonal relations, decision authority, and organizational trust. To describe the ways algorithmic management may influence workers’ health, this review summarizes available literature from public health, sociology, management science, and human-computer interaction studies, highlighting the dimensions of job quality associated with work stress and occupational safety. We focus on the example of work for platform-based food and grocery delivery companies; these businesses are growing rapidly worldwide and their effects on workers and policies to address those effects have received significant attention. We conclude with a discussion of research challenges and needs, with the goal of understanding and addressing the effects of this increasingly used technology on worker health and health equity.

The use of lanthanides, also known as rare earth elements (REEs), in technological devices and their presence in the e-waste made them a new category of potential emerging contaminants (Gravina et al., 2018; Pagano et al., 2019). Their toxicological and ecotoxicological effects are still largely unknown. Erbium is one of the most widespread REEs with potential environmental and human health risks associated to its increased release (Tornero and Hanke, 2017). Reported lanthanides concentrations in the surface water usually vary from 10 ng/L to 200 ng/L (Neal, 2007); however, in the very polluted rivers lanthanides concentrations may increase up to 10 μg/L (Neal et al., 2005). Only few studies investigated the potential effects of REEs on a long-term basis in freshwater (Blaise et al., 2018; Blinova et al., 2018). The aim of our study is to examine the influence of Erbium on Xenopus laevis embryos, organism never experimented with this lanthanide, to test the eventual adverse effects on developing organisms. We used environmental (1 and 10 μg/L) and twice higher (20μg/L) concentrations. Our preliminary data indicate that Erbium induces alteration of morphology, with cephalic and abdominal edema and anomalous intestinal winding, ROS production and decreased heart rate, thus suggesting that erbium could be dangerous for X. laevis and other non-target species.

This work presents an effort to understand and characterize the role moisture content plays in how sound interacts with sand on the beach. This exploratory effort is part of a larger project developing a numerical model of long-range (up to approximately 3 km) atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. Previous experiments have studied moisture content of sand samples taken at various distances from the water’s edge of an artificial beach. This works seeks to perform the same studies in natural coastal areas by recording moisture content in situ via a moisture probe at two depths and conducting testing with an impedance tube. Samples are collected at several distances from the shoreline at high and low tides. The results collected at the natural coastal areas are compared to those obtained from studies at the artificial lake in order to inform a related effort that seeks to capture the acoustic characteristics of the sandy beach for use in numerical modeling efforts. This study shows essentially no tidal influence on beach moisture gradient. The observed distance over which the sand transitioned from saturated to dry was generally less than a few meters.

This work presents a case study of atmospheric acoustic transmission loss measurements over a mixed domain of water and sand. The aim of this paper is a detailed description of the measurement system and data handling approach. This effort is part of an ongoing project modeling atmospheric acoustic transmission loss in littoral or riverine environments. The goal of the presented experiment is the evaluation of the excess attenuation introduced by a sandy shore. The site is a small pond with a man-made sandy beach area. An acoustic source is placed on the opposite edge of the pond and three 7-microphone arrays are placed in line at ranges of 126 m (water’s edge), 146 m and 166 m. Data is presented in order to highlight the design of the measurement system and post-processing approach. Sound pressure levels predicted by a numerical model, which is presented in detail in a companion work, are included as an illustrative case.

This article supports a submission presented at the LRSP 18th International Symposium on Long Range Sound Propagation. This work presents the modeling of excess attenuation of a sandy shore and its contribution to the atmospheric sound transmission loss in a near-shore environment. The numerical model uses a parabolic equation method to account for wind and temperature variation with elevation along the propagation path. The surface impedance of a sandy shore is modeled as an equivalent fluid that takes into account the grain size distribution of the sand and its change in water content along the propagation path. The propagation range consists of three segments: over flat water, over wet sand, and over dry sand. Beach acoustic absorption is modeled with an increasing degree of complexity. Acoustic transmission loss predicted by the proposed model is compared with data. It is found that the simplest model of the beach is sufficient to predict sound pressure levels at the shore up to 20 m far from the water edge. However, a more complicated model is needed to capture the acoustic behavior of the beach at locations further away.

In the most common method of fresco painting, a unique integration of paint and plaster allows for frescos to acquire great durability and permanence. As the plaster or layers of fresco walls deteriorate over time, frescos become vulnerable to serious damage. In order to prevent such damage without harming frescos, non-destructive techniques must be used to analyze and determine areas of structure delamination. In the past, different non-destructive methods have been studied. However, many require expensive equipment. The main scope of this work is the evaluation of the effectiveness of non-invasive detection of fresco delamination via thermography, a comparatively inexpensive technique. In non-invasive active infrared thermography, thermal images are captured of a fresco before, during, and after a heating or cooling process. A defect beneath the surface acts as an insulative pocket, which in turn entraps heat and decreases the rate of heat diffusion. The accumulation of heat results in a defective region being abnormally hotter than a non-defective region, which causes a greater change in temperature throughout a heating or cooling process. Therefore, the analysis of the temperature change highlights defects location and entity beneath the surface. This technique was used and validated with two constructed surrogates, one with a known defect and one without a defect. The thermal analysis of the surrogates was performed via MATLAB®. Additionally, simulations of heating and cooling processes on modeled surrogates were generated in COMSOL® Multiphysics. The results of these simulations assessed the MATLAB® analysis and the use of non-invasive thermography as a tool to detect fresco delaminations. This method was then implemented on frescos within the Senate Reception Room of the United States Capitol Building.

The potential negative effects of sound, particularly active sonar, on marine mammals has received considerable attention in the past decade. Numerous behavioral response studies are ongoing around the world to examine such direct exposures. However, detailed aspects of the acoustic field (beyond simply exposure level) in the vicinity of sonar operations both during real operations and experimental exposures have not been regularly measured. For instance, while exposures are typically repeated and intermittent, there is likely a gradual decay of the intense sonar ping due to reverberation that has not been well described. However, it is expected that the sound field between successive sonar pings would exceed natural ambient noise within the sonar frequency band if there were no sonar activity. Such elevated sound field between the pings may provide cues to nearby marine mammals on source distances, thus influencing potential behavioral response. Therefore, a good understanding of the noise field in these contexts is important to address marine mammal behavioral response to MFAS exposure. Here we investigate characteristics of the sound field during a behavioral response study off California using drifting acoustic recording buoys. Acoustic data were collected before, during, and after playbacks of simulated mid-frequency active sonar (MFAS). An incremental computational method was developed to quantify the inter-ping sound field during MFAS transmissions. Additionally, comparisons were made between inter-ping sound field and natural background in three distinctive frequency bands: low-frequency ( 4.5 kHz) bands. Results indicate significantly elevated sound pressure levels (SPLs) in the inter-ping interval of the MFA-frequency band compared to natural background levels before and after playbacks. No difference was observed between inter-ping SPLs and natural background levels in the low- and high-frequency bands. In addition, the duration of elevated inter-ping sound field depends on the MFAS source distance. At a distance of 900–1300 m from the source, inter-ping sound field at the exposure frequency is observed to remain 5 dB above natural background levels for approximately 15 s, or 65%, of the entire inter-ping interval. However, at a distance of 2000 m, the 5 dB elevation of the inter-ping SPLs lasted for just 7 s, or 30% of the inter-ping interval. The prolonged elevation of sound field beyond the brief sonar ping at such large distances is most likely due to volume reverberation of the marine environment, although multipath propagation may also contribute to this.

Prior work demonstrates that an attached subordinate oscillator array (SOA) can attenuate vibration of a host structure. The distribution of masses and stiffnesses of the attached oscillators can craft a flat frequency response over a desired band. This response modification can be a significant improvement over classical dynamic vibration absorbers (DVA) that attenuate response at one target frequency while increasing the frequency response amplitude at nearby side frequencies. Performance of the SOA can be highly sensitive to the uncertainty or disorder in the mechanical properties of the system. This paper shows that use of piezolectric SOAs (PSOAs) has the potential to address and ameliorate such sensitivity to off-design situations. It is important to note that the design strategy is simple and effective: it can be carried out without optimization techniques by choosing simple or well-known distributions of electromechanical properties.

The interdisciplinary field of assessing the impacts of sound on marine life has benefited largely from the advancement of underwater acoustics that occurred after World War II. Acoustic parameters widely used in underwater acoustics were redefined to quantify sound levels relevant to animal audiometric variables, both at the source and receiver. The fundamental approach for assessing the impacts of sound uses a source-pathway-receiver model based on the one-way sonar equation, and most numerical sound propagation models can be used to predict received levels at marine animals that are potentially exposed. However, significant information gaps still exist in terms of sound source characterization and propagation that are strongly coupled with the type and layering of the underlying substrate(s). Additional challenges include the lack of easy-to-use propagation models and animal-specific statistical detection models, as well as a lack of adequate training of regulatory entities in underwater acoustics.

Offshore oil and gas exploration using seismic airguns generates intense underwater pulses that could cause marine mammal hearing impairment and/or behavioral disturbances. However, few studies have investigated the resulting multipath propagation and reverberation from airgun pulses. This research uses continuous acoustic recordings collected in the Arctic during a low-level open-water shallow marine seismic survey, to measure noise levels between airgun pulses. Two methods were used to quantify noise levels during these inter-pulse intervals. The first, based on calculating the root-mean-square sound pressure level in various sub-intervals, is referred to as the increment computation method, and the second, which employs the Hilbert transform to calculate instantaneous acoustic amplitudes, is referred to as the Hilbert transform method. Analyses using both methods yield similar results, showing that the inter-pulse sound field exceeds ambient noise levels by as much as 9 dB during relatively quiet conditions. Inter-pulse noise levels are also related to the source distance, probably due to the higher reverberant conditions of the very shallow water environment. These methods can be used to quantify acoustic environment impacts from anthropogenic transient noises (e.g., seismic pulses, impact pile driving, and sonar pings) and to address potential acoustic masking affecting marine mammals.

This work presents a comparison between existing weather models and experimental measurements of the lower atmospheric boundary layer. This work is part of a larger project developing a numerical model of long-range (~3 km) atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. Temperature, humidity, and pressure data are collected with the use of iMet-XQ2 sensors mounted on an unmanned aerial vehicle. Vertical measured profiles that will then be compared to existing common models and assumptions (such as Monin-Obukhov similarity theory) to gain a better understanding of these mathematical models and how sufficient these models are at representing the meteorological parameters that will affect acoustic transmission.

This work presents a comparison between experimental results and numerical modeling of atmospheric sound transmission loss across a range that includes water and a sandy shore. This work is part of a larger project developing a numerical model of long-range (∼3 km) atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. The narrow angle parabolic equation method used in this work accounts for wind and temperature variation with elevation along the acoustic propagation path. The beach is modelled as an equivalent fluid employing the Johnson-Champoux-Allard-Pride-Lafarge (JCAPL) model. This eight-parameters model is reduced to a one-parameter model by considering the sand as randomly packed spherical particles. The single parameter is the grain size. Measured grain size distributions of the sand and its change in water content with the distance from the water inform model development of the beach. Sound pressure levels predicted by three model variations are compared with measurements. Advantages and drawbacks of model complexity are presented. We show that short spans of saturated sand are effectively modelled with a fully reflective surface whereas longer spans of sand require varying levels of sound absorption.

This work presents an effort to understand and characterize the role moisture content plays in how sound interacts with sand on the beach. This work is part of a larger project developing a numerical model of long-range (~3 km) atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. Previous experiments have studied the effects of moisture content of sand samples taken from various distances from the water's edge of a man-made lake with an artificial beach. This works seeks to perform the same studies in natural coastal areas by recording moisture content on site via a moisture probe at several depths, collecting samples to determine gravimetric water content of a bulk sample, and conducting testing with an impedance tube. Samples will be collected at various distances from the shoreline in order to inform a related effort that seeks to capture the acoustic characteristics of the sandy beach for use numerical modeling.

Subordinate Oscillator Arrays (SOAs) have been shown to be effective methods for band-limited vibration attenuation. However, SOAs are very sensitive to error in parameter distributions. Slight disorder in structural parameters can render an SOA ineffective. Recent research has shown that Piezoelectric SOAs (PSOAs) provide an alternative that can limit the degradation of the frequency response function due to the disorder. The capacitive shunts attached to such SOAs can be tuned to change overall electromechanical properties of the SOA post-fabrication. The conventional methods of tuning, which study the Frequency Response Function (FRF) of each oscillator in the array, can be an extremely time-consuming process. To apply a systematic approach to tuning, an estimate of the disorder in structural property distributions can be crucial. In this paper, we discuss a simple and effective methodology to estimate the actual structural parameters and subsequently tune the PSOA to ameliorate the effect of disorder. We derive an adaptive estimation technique for PSOAs and present numerical results that demonstrate improved vibration attenuation of this approach.

Pile driving is used for constructing foundation supports for offshore structures. Underwater noise, induced by in-water pile driving, could adversely impact marine life near the piling location. Many studies have computed this noise in close ranges by using semi-analytical models and Finite Element Method (FEM) models. This work presents a Spectral Element Method (SEM) wave simulator as an alternative simulation tool to obtain close-range underwater piling noise in complex, fully three-dimensional, axially-asymmetric settings in the time domain for impacting force signals with high-frequency contents (e.g., frequencies greater than 1000[Formula: see text]Hz).The presented numerical results show that the flexibility of SEM can accommodate the axially-asymmetric geometry of a model, its heterogeneity, and fluid-solid coupling. We showed that there are multiple Mach Cones of different angles in fluid and sediment caused by the difference in wave speeds in fluid, a pile, and sediment. The angles of Mach Cones in our numerical results match those that are theoretically evaluated. A previous work18had shown that Mach Cone waves lead to intense amplitudes of underwater piling noise via a FEM simulation in an axis-symmetric setting. Since it modeled sediment as fluid with a larger wave speed than that of water, we examined if our SEM simulation, using solid sediment–fluid coupling, leads to additional Mach Cones. Because this work computes the shear wave in sediment and the downward-propagating shear wave in a pile, we present six Mach Cones in fluid and sediment induced by downward-propagating P- and S-waves in a pile in lieu of two previously-reported Mach Cones in fluid and sediment (modeled as fluid) induced by a downward-propagating P-wave in a pile. We also showed that the amplitudes of the close-range underwater noise are dependent on the cross-sectional geometry of a pile. In addition, when a pile is surrounded by a solid of an axially-asymmetric geometry, waves are reflected from the surface of the surrounding solid back to the fluid so that constructive and destructive interferences of waves take place in the fluid and affect the amplitude of the underwater piling noise.

In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments.

The underwater acoustic field is an important ecological element for many aquatic animals. This research examines the soundscape of a critically endangered Indo-Pacific humpback dolphin population in the shallow water environment off the west coast of Taiwan. Underwater acoustic recordings were conducted between late spring and late fall in 2012 at Yunlin (YL), which is close to a shipping lane, and Waisanding (WS), which is relatively pristine. Site-specific analyses were performed on the dynamics of the temporal and spectral acoustic characteristics for both locations. The results highlight the dynamics of the soundscape in two major octave bands: 150-300 Hz and 1.2-2.4 kHz. The acoustic energy in the former frequency band is mainly associated with passing container vessels near YL, while the latter frequency band is from sonic fish chorus at nighttime in both recording sites. In addition, large variation of low frequency acoustic energy throughout the study period was noticed at WS, where the water depths ranged between 1.5 and 4.5 m depending on tidal cycle. This phenomenon suggests that besides certain sound sources in the environment, the coastal soundscape may also be influenced by its local bathymetry and the dynamics of the physical environment.

Subordinate Oscillator Arrays (SOAs) can be shown theoretically to provide vibration attenuation that is characterized by a frequency response function with a magnitude that is approximately flat over a finite bandwidth. However, the actual performance of SOA designs can suffer due to uncertainties in the structural parameters of the host and SOA. In this paper, we describe a piezoelectric composite SOA that can be used either actively or passively to account or correct for uncertainties in structural parameters that result from fabrication. This paper uses thermodynamic variational principles to derive the equations of motion for the active SOA formed using piezoelectric composites. We discuss techniques to optimize vibration attenuation for the SOA with fabrication errors using the piezoelectric appendages in the SOA.

One approach for non-contact interrogation of mixed-media surfaces, such as fresco, is mapping surface motion induced by acoustic excitation. A scanning laser Doppler vibrometer provides such high spatial resolution surface information which can indicate material inclusions, delaminations, and other subsurface features. This work uses this interrogation method on frescos in the U.S. Capitol Building. These frescos were installed in the mid nineteenth century under the supervision of Italian artist Constantino Brumidi. Brumidi and his team used traditional fresco techniques for their work throughout the U.S. Capitol Building. Specifically, this work focuses on the Senate Reception Room. Such maps of these frescos were completed in 2004. In the intervening years, external events may have changed the fresco integrity. Such events include restoration work performed by the Office of the Architect of the Capitol and the Mw 5.8 earthquake in Mineral, Virginia in 2011. These repeat measurements allow for an assessment of changes due to these events. While these measurements can only locate the region of anomaly, an inverse analysis is required to classify the nature of the anomaly. Therefore, in addition to measurements, numerical finite element simulations are used to classify the type, size, and location of defects.

The vibration transmitted to the payload of a rocket vehicle during liftoff is large in magnitude and broad in frequency. Delicate parts of a satellite like solar panels, lenses, and other equipment carried to perform specific missions can easily be damaged during liftoff. Passive damping systems are currently used to isolate the delicate payload from vibration. However, energy can be dissipated in a narrow frequency band using a Subordinate Oscillator Array (SOA). The SOA is an array of cantilever beams of different size and mass that are attached on a primary resonant structure. The subordinate beams are substantially smaller than the primary structure. This arrangement allows energy transmitted to the primary structure to be dissipated down scale through the vibration of the array of smaller structures. In this study, an SOA is designed to isolate one face of a CubeSat (a cubic satellite of dimensions 10 × 10 × 10 cm) from the broadband vibrations transmitted during the launch of its rocket carrier. Simulation using COMSOL Multiphysics is used to analyze and quantify the effectiveness of this absorber. These numerical results are compared to scanning laser Doppler vibrometry measurements of prototype SOAs affixed to a plate designed to mimic the CubeSat face.The vibration transmitted to the payload of a rocket vehicle during liftoff is large in magnitude and broad in frequency. Delicate parts of a satellite like solar panels, lenses, and other equipment carried to perform specific missions can easily be damaged during liftoff. Passive damping systems are currently used to isolate the delicate payload from vibration. However, energy can be dissipated in a narrow frequency band using a Subordinate Oscillator Array (SOA). The SOA is an array of cantilever beams of different size and mass that are attached on a primary resonant structure. The subordinate beams are substantially smaller than the primary structure. This arrangement allows energy transmitted to the primary structure to be dissipated down scale through the vibration of the array of smaller structures. In this study, an SOA is designed to isolate one face of a CubeSat (a cubic satellite of dimensions 10 × 10 × 10 cm) from the broadband vibrations transmitted during the launch of its rocket carrier. Si...

This work will investigate two non-destructive methods of fault detection in laminate structures such as frescos. These two techniques are compared on a purpose-built laboratory prototype and on frescos in the Senate Reception Room of the U.S. Capitol Building. Thermography uses an infrared camera to map the surface temperature of an object. This technique can be used to quickly identify abnormally hot or cold regions on a surface. These abnormal regions can indicate structural defects such as fresco delamination, cracks, and inclusions. The other non-destructive technique for defect detection used in this work is laser Doppler vibrometry paired with acoustic excitation of the target surface. Over the same surface area, thermography provides a much quicker result. This work aims to evaluate potential synergy between the technologies by comparing the results of the two scans. A prototype with known defects is used to find commonality between the two methods and to understand the circumstances in which the results diverge. The prototype is a square of approximately half a meter on each side. A seven centimeter thick concrete backing layer is followed by a layer of mortared antique bricks and topped by mortar and plaster to mimic fresco.This work will investigate two non-destructive methods of fault detection in laminate structures such as frescos. These two techniques are compared on a purpose-built laboratory prototype and on frescos in the Senate Reception Room of the U.S. Capitol Building. Thermography uses an infrared camera to map the surface temperature of an object. This technique can be used to quickly identify abnormally hot or cold regions on a surface. These abnormal regions can indicate structural defects such as fresco delamination, cracks, and inclusions. The other non-destructive technique for defect detection used in this work is laser Doppler vibrometry paired with acoustic excitation of the target surface. Over the same surface area, thermography provides a much quicker result. This work aims to evaluate potential synergy between the technologies by comparing the results of the two scans. A prototype with known defects is used to find commonality between the two methods and to understand the circumstances in which the ...

This work presents advances in the development of a numerical model of atmospheric acoustic propagation designed for a littoral or riverine environment with a near-shore acoustic source and on-shore receivers. A parallel experimental effort uses a measurement system that records concurrent atmospheric and acoustic transmission loss data. The numerical model uses a generalized terrain parabolic equation method to account for sea surface roughness and ground topography along the propagation path. The model accounts for vertical temperature and wind speed profiles as well as surface impedance at the shore. For the comparison with experimental data, wind speed is used to predict the sea state. The propagation range consists of three segments: over water, over swash and sandy shore, and over complex dune with highly varied vegetation of up to 2 m height. Surface impedance estimates for the sandy shore are made based on grain size distribution and impedance tube measurements of excised samples. Existing models for surface impedance of vegetation were used for the dune portion of the propagation range.This work presents advances in the development of a numerical model of atmospheric acoustic propagation designed for a littoral or riverine environment with a near-shore acoustic source and on-shore receivers. A parallel experimental effort uses a measurement system that records concurrent atmospheric and acoustic transmission loss data. The numerical model uses a generalized terrain parabolic equation method to account for sea surface roughness and ground topography along the propagation path. The model accounts for vertical temperature and wind speed profiles as well as surface impedance at the shore. For the comparison with experimental data, wind speed is used to predict the sea state. The propagation range consists of three segments: over water, over swash and sandy shore, and over complex dune with highly varied vegetation of up to 2 m height. Surface impedance estimates for the sandy shore are made based on grain size distribution and impedance tube measurements of excised samples. Existing models ...

This paper presents the adaptation of the Cross Ambiguity Function Mapping (CAF- Mapping) algorithm for use in acoustics. The CAF-Mapping algorithm provides a useful means of generating a geographic visualization of acoustic data. Modifications of the algorithm for use in acoustics are explained, including use of acoustic modeling to generate propagation time differences, nonlinear grid spacing for frequency differences, location seeding using either three sensors or two sensors and two data samples, and frequency normalization. The algorithm allows discrimination between multiple acoustic signals with spatial or velocity vector variance. The presentation compares simulation results for several different types of data, then provides results that track a likely group of pygmy blue whale (Balaenoptera musculus brevicauda) using data from the Comprehensive Test Ban Treaty (CTBT) sensors off the coast of Australia. The author's affiliation with The MITRE Corporation is provided for identification purposes only and is not intended to convey or imply MITRE's concurrence with, or support for, the positions, opinions, or viewpoints expressed by the author. [Approved for Public Release; Distribution Unlimited Case 19-1301. Copyright 2019, The MITRE Corporation.]This paper presents the adaptation of the Cross Ambiguity Function Mapping (CAF- Mapping) algorithm for use in acoustics. The CAF-Mapping algorithm provides a useful means of generating a geographic visualization of acoustic data. Modifications of the algorithm for use in acoustics are explained, including use of acoustic modeling to generate propagation time differences, nonlinear grid spacing for frequency differences, location seeding using either three sensors or two sensors and two data samples, and frequency normalization. The algorithm allows discrimination between multiple acoustic signals with spatial or velocity vector variance. The presentation compares simulation results for several different types of data, then provides results that track a likely group of pygmy blue whale (Balaenoptera musculus brevicauda) using data from the Comprehensive Test Ban Treaty (CTBT) sensors off the coast of Australia. The author's affiliation with The MITRE Corporation is provided for identification purposes onl...

A model for moderate to long range outdoor propagation of sound in complex environments must account for a wide variety of parameters. Generally, the characteristics of the source, the space through which the sound propagates, and the receiver must all be considered. This larger project aims to understand atmospheric acoustic transmission loss in the littoral and riverine environments at ranges of up to approximately 3 km. In such an environment, some of the confounding factors in the propagation path include: wind speed and direction, temperature and humidity profiles, absorption, refraction, dispersion, turbulence, diffraction, dynamically changing water surface geometry, shore terrain geometry and surface impedance along the propagation path. A simple pitch-catch configuration with the source over water and the microphone arrays on shore is used to capture transmission loss information, along with concurrent meteorological measurements. In this work, the measurement system is described and preliminary results from measurements at three sites are reported. These measurements inform the concurrent effort to develop and validate an improved model for acoustic transmission loss in these scenarios.

In this study, we model acoustic waves induced by moving acoustic sources in three-dimensional (3D) underwater settings based on a spectral-element method (SEM). Numerical experiments are conducted using the SEM software package SPECFEM3D_Cartesian, which facilitates fluid–solid coupling and absorbing boundary conditions. Examples presented in this paper include an unbounded fluid truncated by using absorbing boundaries, and a shallow-water waveguide modeled as a fluid–solid coupled system based on domain decomposition. In the numerical experiments, the SEM-computed pressures match their analytical counterparts. SEM solutions of pressures at points behind and ahead of modeled moving acoustic sources show a frequency shift, i.e., a Doppler effect, which matches the analytical solution. This paper contributes to the field of passive sonar-based detection of moving acoustic sources, and addresses the challenge of computing wave responses generated by side-scan sonar by using moving sources of continuous signals.

Subordinate Oscillator Arrays (SOAs) attached to a host structure have been shown to achieve flat attenuation of the frequency response over a band around a target natural frequency of the host. Due to their sensitivity to disorders that can arise from sources such as fabrication errors, as well as uncertainties in their structural properties or that of the host, SOAs can be challenging to implement in some applications. To overcome this shortcoming, Piezoelectric Subordinate Oscillator Arrays (PSOAs) are studied in this paper. This paper models PSOAs using variational principles to facilitate the analysis and development of design strategies. A closed-form expression for the frequency response function of the host structure is then used to design the PSOAs with and without uncertainties. This paper shows that the flat attenuation over a frequency band around a harmonic of the host can be achieved by assigning a distribution to the mechanical, electrical, or electromechanical properties of the PSOAs. For instance, it is shown that choosing a distribution of capacitive shunt circuits can achieve essentially the same qualitatively flat attenuation as that of classical SOAs. In this sense, the approach in this paper generalizes the results attained for conventional SOAs. Finally, the paper investigates the robustness of PSOAs, that is, their relative insensitivity to types of uncertainties. It is shown that PSOAs afford the chance to ameliorate some types of sensitivities that prove problematic for SOAs that are purely mechanical in nature. The notion of performance recovery is introduced; this measure quantifies how much attenuation loss due to uncertainty in an initial SOA or PSOA design can bea#13; recovered by modification of the electrical properties alone.