Multi-Modal and Short-Range Transmission Loss in Ice-Covered, Near-Shore Arctic Waters

In the past century, extensive research has been done regarding the sound propagation in arctic ice sheets. The majority of this research has focused on low frequency propagation over long distances. One of the most commonly used excitation methods for air-ice-water layers has been explosives. However, environmental regulation has become more stringent, disallowing the use of almost all explosive excitation types. Due to changing climate conditions in these environments, new experimentation is warranted to determine sound propagation characteristics in, through, and under thin ice sheets, in shallow water, over short distances. In April, 2016 several experiments were conducted approximately 2 km off the coast of Barrow, Alaska on shore-fast, first year ice, approximately 1 m thick. To determine the propagation characteristics of various sound sources, Frequency Response Functions (FRFs) were measured between a source location and several receiver locations at various distances from 1 m to 1 km. The primary sources used for this experiment were, an underwater speaker with various tonal outputs, an instrumented impact-hammer on the ice, and a propane cannon that produced an acoustic blast wave in air. The transmission characteristics of the multipath propagation (air, ice, water) are investigated and reported

ACOUSTIC LOCALIZATION TECHNIQUES FOR APPLICATION IN NEAR-SHORE ARCTIC ENVIRONMENTS

The Arctic environment has undergone significant change in recent years. Multi-year ice is no longer prevalent in the Arctic. Instead, Arctic ice melts during summer months and re-freezes each winter. First-year ice, in comparison to multi-year ice, is different in terms of its acoustic properties. Therefore, acoustic propagation models of the Arctic may no longer be valid. The open water in the Arctic for longer time periods during the year invites anthropogenic traffic such as civilian tourism, industrial shipping, natural resource exploration, and military exercises. It is important to understand sound propagation in the first-year ice environment, especially in near-shore and shallow-water regions, where anthropogenic sources may be prevalent. It is also important to understand how to detect, identify, and track the anthropogenic sources in these environments in the absence of large acoustic sensory arrays. The goals of this dissertation are twofold: 1) Provide experimental transmission loss (TL) data for the Arctic environment as it now exists, that it may be used to validate new propagation models, and 2) Develop improved understanding of acoustic vector sensor (AVS) performance in real-world applications such as the first-year Arctic environment. Underwater and atmospheric acoustic TL have been measured in the Arctic environment. Ray tracing and parabolic equation simulations have been used for comparison to the TL data. Generally good agreement is observed between the experimental data and simulations, with some discrepancies. These discrepancies may be eliminated in the future with the development of improved models. Experiments have been conducted with underwater pa and atmospheric pp AVS to track mechanical noise sources in real-world environments with various frequency content and signal to noise ratio (SNR). A moving standard deviation (MSD) processing routine has been developed for use with AVS. The MSD processing routine is shown to be superior to direct integration or averaging of intensity spectra for direction of arrival (DOA) estimation. DOA error has been shown to be dependent on ground-reflected paths for pp AVS with analytical models. Underwater AVS have been shown to be feasible to track on-ice sources and atmospheric AVS have been shown feasible to track ground vehicle sources

What is an "adult protection" issue? Victims, perpetrators and the professional construction of adult protection issues

Drawing on data from a Scottish research study, this paper explores the relationship of professionals’ perceptions about specific perpetrators and victims to their constructions of ‘adult protection’ issues in practice. It finds that professionals’ perceptions of victim distress did not consistently coincide with the construction of adult protection issues, whilst the connection to any assessment of victims’ heightened vulnerability in specific cases was not clear. With respect to perpetrators, implicit practice rules were evidenced which differed from explicit policy criteria. In particular, there were different rules for relatives, staff and service user perpetrators, whilst harms attributed to institutions were de-emphasized. Explanations of the findings are advanced based on the complex power relations underpinning practice but unacknowledged in policies. More research is recommended to deepen this analysis in a changing policy context, to foreground service user perspectives, and to contextualize harms potentially resolvable through adult support and protection/safeguarding routes with respect to harms better addressed in other ways

Direction of arrival estimation in practical scenarios using moving standard deviation processing for localization and tracking with acoustic vector sensors

Typical direction of arrival (DOA) estimation is done with sensor arrays consisting of a great number of sensors. It is of interest to perform DOA estimation with few sensor locations. Acoustic vector sensors (AVS) provide one option for DOA estimation in applications where few sensor locations are required. The majority of AVS experiments have focused on stationary sources in laboratory environments where the source signature is known and controlled. Experiments in this paper have been conducted with in-air pressure-pressure (pp) AVS to track moving mechanical noise sources (ground vehicles) in real-world environments with various frequency content and signal to noise ratio. A moving standard deviation (MSD) algorithm has been used with AVS to estimate DOA at multiple sites. Azimuthal DOA accuracy has been shown to be dependent on ground-reflected paths for pp AVS with comparison to analytical models. Utilizing multiple AVS sites, in-air pp AVS are demonstrated to localize sources with complex signatures

Multi-modal and short-range transmission loss in thin, ice-covered, near-shore Arctic waters

In the past century, extensive research has been done regarding the sound propagation in Arctic ice sheets. The majority of this research has focused on low-frequency propagation over long distances. Due to changing climate conditions in these environments, experimentation is warranted to determine sound propagation characteristics in, through, and under first-year, thin ice sheets, in shallow water, over short distances. In April 2016 several experiments were conducted approximately 2 km off the coast of Barrow, Alaska on shore-fast, first-year ice, approximately 1 m thick. To determine the propagation characteristics of various sound sources, frequency response functions were measured between a source location and several receiver locations at various distances from 1 m to 1 km. The primary sources used for this experiment were, an underwater speaker with various tonal outputs, an instrumented impact hammer on the ice, and a propane cannon that produced an acoustic blast wave in air. The transmission loss (TL) characteristics of the multipath propagation (air, ice, water) are investigated and reported. Data indicate that TL in frequency bands between 125 and 2000 Hz varied from approximately 3-6 dB per doubling of distance which is consistent with geometrical spreading losses, cylindrical and spherical, respectively

Elder Homicide in the UK (2010–2015): A Gendered Examination

Despite public fascination with homicide, academic research remains comparatively lacking compared to the widespread media coverage of such offences. In particular, homicide involving older adults has received very little attention. Drawing on a Freedom of Information study in the UK, this chapter reports on 514 homicides recorded between 2010 and 2015 involving victims over the age of 59. Analysis of these cases revealed that homicide of older men is qualitatively different to homicide of older women, confirming the need for a gendered analysis of homicides across the life course. Using this novel study to illustrate our argument, we suggest there are several issues to be addressed concerning conceptualisations of violence against older people as well as methodological challenges to overcome. Implications for research, policy and practice are discussed