MULTI-access techniques have been adopted widely for communications in underwater acoustic channels, which present many challenges to the development of reliable and practical systems. In such an environment, the unpredictable and complex ocean conditions cause the acoustic waves to be affected by many factors such as limited bandwidth, large propagation losses, time variations and long latency, which limit the usefulness of such techniques. Additionally, multiple access interference (MAI) signals and poor estimation of the unknown channel parameters in the presence of limited training sequences are two of the major problems that degrade the performance of such technologies. In this thesis, two different single-element multi-access schemes, interleave division multiple access (IDMA) and code division multiple access (CDMA), employing decision feedback equalization (DFE) and soft Rake-based architectures, are proposed for multi-user underwater communication applications. By using either multiplexing pilots or continuous pilots, these adaptive turbo architectures with carrier phase tracking are jointly optimized based on the minimum mean square error (MMSE) criterion and adapted iteratively by exchanging soft information in terms of Log-Likelihood Ratio (LLR) estimates with the single-user’s channel decoders. The soft-Rake receivers utilize developed channel estimation and the detection is implemented using parallel interference cancellation (PIC) to remove MAI effects between users. These architectures are investigated and applied to simulated data and data obtained from realistic underwater communication trials using off-line processing of signals acquired during sea-trials in the North Sea. The results of different scenarios demonstrate the penalty in performance as the fading induces irreducible error rates that increase with channel delay spread and emphasize the benefits of using coherent direct adaptive receivers in such reverberant channels. The convergence behaviour of the detectors is evaluated using EXIT chart analyses and issues such as the adaptation parameters and their effects on the performance are also investigated. However, in some cases the receivers with partial knowledge of the interleavers’ patterns or codes can still achieve performance comparable to those with full knowledge. Furthermore, the thesis describes implementation issues of these algorithms using digital signal processors (DSPs), such as computational complexity and provides valuable guidelines for the design of real time underwater communication systems.

Autonomous Underwater Vehicles (AUVs) are increasingly used in different domains including archaeology, oil and gas industry, coral reef monitoring, harbour’s security, and mine countermeasure missions. As electromagnetic signals do not penetrate underwater environment, GPS signals cannot be used for AUV navigation, and optical cameras have very short range underwater which limits their use in most underwater environments. Motion estimation for AUVs is a critical requirement for successful vehicle recovery and meaningful data collection. Classical inertial sensors, usually used for AUV motion estimation, suffer from large drift error. On the other hand, accurate inertial sensors are very expensive which limits their deployment to costly AUVs. Furthermore, acoustic positioning systems (APS) used for AUV navigation require costly installation and calibration. Moreover, they have poor performance in terms of the inferred resolution. Underwater 3D imaging is another challenge in AUV industry as 3D information is increasingly demanded to accomplish different AUV missions. Different systems have been proposed for underwater 3D imaging, such as planar-array sonar and T-configured 3D sonar. While the former features good resolution in general, it is very expensive and requires huge computational power, the later is cheaper implementation but requires long time for full 3D scan even in short ranges. In this thesis, we aim to tackle AUV motion estimation and underwater 3D imaging by proposing relatively affordable methodologies and study different parameters affecting their performance. We introduce a new motion estimation framework for AUVs which relies on the successive acoustic images to infer AUV ego-motion. Also, we propose an Acoustic Stereo Imaging (ASI) system for underwater 3D reconstruction based on forward looking sonars; the proposed system features cheaper implementation than planar array sonars and solves the delay problem in T configured 3D sonars.

Closed-circuit television (CCTV) cameras have become a ubiquitous feature of everyday life in the UK over the last thirty years. In this thesis I undertake an examination of the historical, political, social, economic, and technological factors, influencing the development, usage, and widespread dissemination of CCTV in the UK. I focus on the issue of why the UK has become so camera-surveilled, and especially the specific role that the public has played in relation to the development and use of the technology. I examine the historical factors through an analysis of the development of surveillance, policing, and political change, during the 20th and early 21st centuries, and early and contemporary uses of CCTV, situating this in the wider context of a history of the criminal justice system. I also look at the media and policy context in which CCTV has developed and become widespread, with this element of the thesis particularly informed by an analysis of the way in which the public are constructed. Next, I carry out an empirical study exploring public engagement and consultation in relation to, and feelings towards, the installation of CCTV onto two estates in East London as part of a project to expand access to digital services in London. Finally, I give an overview of international experiences of CCTV providing a broader context for the final analysis. I argue that the lack of legislation and regulation at the time of the inception of CCTV allowed its subsequent and rapid proliferation. The initial growth of CCTV also occurred at a time when public debate and engagement in science and technology policy did not take place. Its use as a tool for crime prevention was cemented by a police force looking for a shoulder to share the burden of fighting crime. This coupled with an availability of public money for the installation of CCTV systems, the need for a political solution to rising levels of crime, and an apparently passive public, formed the ideal environment for the rise of CCTV.

This thesis is a study of audio technology community discourse and its historical features. I contend that the audio technology domain is fundamentally exclusive and hierarchically stratified, based on discursively inscribed prerequisites to participation and enunciation, notably a hegemonic masculine performance, gear fetishism and the articulation of technical knowledge. I show that communities organised around audio technology, socially construct and perpetuate these features as components of their respective discourses. I expose all three elements to be rooted in culturally embedded gender stereotypes, dating back to a nineteenth century dichotomy of public and private space. I present a deconstruction of the complex discursive performances of masculinity and offer opportunities for privileged masculine recordists to critically reflect upon their dominance and homogeneity within the domain as an original contribution to knowledge. In this endeavour, I investigate the emergence and development of exclusive tropes as components of audio technology culture, and demonstrate how they continue to be perpetuated in the face of both social and technological developments that offer possibilities to destratify the community hierarchy and enunciative function. My methodology is based on a comparative discourse analysis of industry and academic texts, as well as the communities that surround and influence the construction of modern audio technology discourse. Case studies are conducted of two leading industry publications: Tape Op and Sound On Sound, and supplemented by an exploration of Women's Audio Mission. I combine these sources with interview material gathered from relevant industry professionals. In doing so, I observe how the audio technology community has maintained barriers to participation, often in the face of technological progress that offers supposed opportunities for democratisation. My work presents an argument against this notion, exposing the supposed democratisation as an illusion of accessibility and thus as mere massification.

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This thesis investigates the application of perceptual models to areas of audio engineering, with a particular focus on music production. The goal was to establish efficient and practical tools for the measurement and control of the perceived loudness of musical sounds. Two types of loudness model were investigated: the single-band model and the multiband excitation pattern (EP) model. The heuristic single-band devices were designed to be simple but suffciently effective for real-world application, whereas the multiband procedures were developed to give a reasonable account of a large body of psychoacoustic findings according to a functional model of the peripheral hearing system. The research addresses the extent to which current models of loudness generalise to musical instruments, and whether can they be successfully employed in music applications.

Video surveillance is a rapidly growing area that has been fuelled by an increase in the concerns of security and safety in both public and private areas. With heighten security concerns, the utilization of video surveillance systems spread over a large area is becoming the norm. Surveillance of a large area requires a number of cameras to be deployed, which presents problems for human operators. In the surveillance of a large area, the need to monitor numerous screens makes an operator less effective in monitoring, observing or tracking groups or targets of interest. In such situations, the application of computer systems can prove highly effective in assisting human operators. The overall aim of this thesis was to investigate different methods for tracking a target across an array of cameras. This required a set of parameters to be identified that could be passed between cameras as the target moved in and out of the fields of view. Initial investigations focussed on identifying the most effective colour space to use. A normalized cross correlation method was used initially with a reference image to track the target of interest. A second method investigated the use of histogram similarity in tracking targets. In this instance a reference target’s histogram or pixel distribution was used as a means for tracking. Finally a method was investigated that used the relationship between colour regions that make up a whole target. An experimental method was developed that used the information between colour regions such as the vector and colour difference as a means for tracking a target. This method was tested on a single camera configuration and multiple camera configuration and shown to be effective. In addition to the experimental tracking method investigated, additional data can be extracted to estimate a spatial map of a target as the target of interest is tracked across an array of cameras. For each method investigated the experimental results are presented in this thesis and it has been demonstrated that minimal data exchange can be used in order to track a target across an array of cameras. In addition to tracking a target, the spatial position of the target of interest could be estimated as it moves across the array.

This thesis analyses the benefits of using object-based audio as a production and delivery format in order to enable new audience experiences. This is achieved though a series of case studies, each focusing on a different user experience enabled by the use of object-based audio. Each study considers the impact of using object-based audio on the creative process, production workflow and audience experience. The first study analyses the audience’s use of the ability to personalise the mix of a live football match. It demonstrates that there was not a single audio mix favoured by all, and the ability to change the mix was valued by the audience. While listeners did adjust the mix initially, they tended to leave it at that setting and did not interact much once they made their initial selection. While there were three favoured mixes, over 50% of listeners did not choose one of these three mixes, indicating that only offering three options would not satisfy everyone. Modes of listening model the ways listeners deconstruct complex sound scenes into foreground and background categories ascribing different salience to foreground and background sounds. The second study uses this model to inform a series of card sorting exercises which result in similar foreground and background categories. However, rather than being unimportant, background sounds were present to convey ancillary information or to affect emotional responses and foreground sounds to expose plot or story events. This study demonstrated that this grouping was a meaningful categorisation for broadcast sound and evaluated how beneficial allowing different foreground and background audio mixes would be for audiences. It contains analysis of audio objects in the context of foreground and background sounds based on the opinions of the content creators. It also includes subjective testing of audience preferences for different mixes of foreground verses background audio levels across five different genres and four different loudspeaker layouts. It shows that there is no clustering of listeners based on their preference of foreground vs background balances. It also shows that there is significant variation of foreground and background balance preference between loudspeaker layouts. The final study goes beyond tailoring audio levels, balances and loudspeaker layouts and analyses the benefit to audiences of being able to adapt the story of a drama in order to set it in a location that is familiar to the listener. It shows that being able to set a radio drama in the location where the listening is taking place improves audience’s enjoyment of the programme. 75% of listeners who experienced the tailored version of the drama reported liking the story, compared with 65% of listeners who experienced a non-tailored version. The three studies also analyse the impact of object-based content creation on production workflows by documenting the challenges faced and discussing possible solutions. For example, providing writers with constraints when they are designing dynamic content and allowing sound designers time to develop trust in the technology when mixing content for multiple loudspeaker layouts. The original contribution to knowledge is to establish a new listening model applicable to constructed and designed sound experiences based on functional analysis of audio objects. This work also establishes, for the first time, a framework for the definition of an audio object based on the creator’s intended range of audience experiences. In addition the thesis also provides insights into how audiences interact with object-based content experiences and insights about audience attitudes towards using personal data to personalise object-based content experiences. Each study addresses the potential advantages of delivering object-based audio, assess any impact on the quality of the audience’s experience and analyses the challenges faced by production in the creation of these new experiences.

This thesis presents the research and subsequent development of a real life system capable of identifying and monitoring objects for user-specified scenarios in live CCTV video. More specifically, after a review of the state of the art in both academic methods and commercial systems, two main novel aspects of the proposed system are detailed. The first deals with the detection of vehicles in static images using a combination of features including: corners, lines and colour. The second aspect relates to how motion has been exploited to detect and track objects within video feeds. The research took place as part of a Knowledge Transfer Partnership, the partner company of which had access to many video feeds across a range of different geographical locations. This provided the opportunity elicit requirements from the actual end-users and to extensively test and evaluate the system on real data. Results from both video and static analysis systems are demonstrated and evaluated before the Thesis concludes with specific enhancements that could be made to the current system and general recommendations for future work.

A study of a new paradigm for a heat assisted magnetic recording (HAMR) media based on the use of exchange bias is presented. Exchange bias occurs when an antiferromagnetic (AF) layer such as IrMn is grown in contact with a ferromagnetic (F) layer and the system if field cooled resulting in a hysteresis loop shifted along the field axis. In this concept the temperature dependent anisotropy is provided by IrMn. Therefore the information is stored in the AF layer and the recording layer is actually part of the read/write structure when field cooled. The F layer when magnetised, serves to align the F layer in the direction required to store the information and then provides a read out signal indicating in which direction the AF layer is oriented. Hence in a complex way the “recording layer” is actually part of the read/write head. The key to achieve a structure of this kind is the control of the orientation of the Mn ions of the IrMn such that they are aligned perpendicular to the plane of the film. In this way a perpendicular exchange bias required for information storage in the AF layer has been achieved. Over 300 samples have been prepared and evaluated to determine the optimised structure. A segregated sample CoCrPt-SiO2 was sputtered using a pressed powder target in a HiTUS deposition system. Dual Ru seed layers of 8nm and 12nm were deposited using 3mTorr and 30mTorr process pressure, respectively. The median grain size of D_m = (6.2 ± 0.2)nm was achieved using these sputtering conditions. High resolution cross section TEM imaging has been used to show that the CoCrPt grains remains segregated by SiO2 after the deposition of IrMn. The key feature of this media is that the recorded information is impossible to be erased by a demagnetising field. In order to achieve this requirement the hysteresis loop has to be completely shifted to a negative field. The highest shift or exchange bias of H_ex = (240 ± 5)Oe was measured at room temperature. This was achieved by depositing an ultrathin (0.8nm) Co interlayer above a Pt seed layer.