996 resultados para Sound propagation


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Participatory and socially engaged art practices have, for a couple of decades, emerged a myriad of aesthetic and methodological strategies across different media. These are artistic practices that have a primary interest in participation, affecting social dynamics, dialogue and at times political activism. Nato Thompson in “Living Form: Socially Engaged Art from 1991-2011” surveys these
practices, which range from theatre to urban planning, visual art to healthcare. Linked to notions such as relational aesthetics (Bourriaud, 1998), community art and public art, socially engaged art often focuses on the development of a sense of ownership by the part of participants. If an artist is working truly collaboratively with participants and addressing the reality of a particular community, the long-term effect of a project lies in the process of engagement as well as in the artwork itself. Projects by New York based artist Pablo Helguera, for example, use different media to engage with social inequalities through participative action while rejecting the notion of art for art sake.

“Socially engaged art functions by attaching itself to subjects and problems that normally belong to other disciplines, moving them temporarily into a space of ambiguity. It is this temporary snatching away of subjects into the realm of art-making that brings new insights to a particular problem or condition and in turn makes it visible to other disciplines.” (Helguera, 2011)

Socially engaged practices develop the notion of artwork about or by a community, to work of a community. In this chapter we address how socially engaged, participatory approaches can form a context for the sonic arts, arguably less explored than practices such as theatre and performance art. The use of sound is clearly present in a wide range of socially engaged work (e.g. Helguera’s “Aelia Media” enabling a nomadic radio station in Bologna or Maria Andueza “Immigrant Sounds – Res(on)Art (Stockholm)” exploring ways of sonically resonating a city, or Sue MacCauley’s “The Housing Project” addressing ways of representing the views of urban dwellers on public scape through sound art. It is nevertheless rare to encounter projects which take our experience of sound in the everyday as a trigger for community social engagement in a participatory context.
We address concepts and methodologies behind the project Som da Maré, a participatory sonic arts project in the favelas of Maré, Rio de Janeiro.

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Recently, gap waveguides have been shown as a potential alternative to conventional waveguides in the millimeterwave band. Until now, Groove Gap Waveguide (GGW) has been studied through direct correspondence with rectangular waveguide with the same physical dimensions. However there have been observed differences in the above cutoff propagation characteristics between these two waveguide types. Furthermore, the behavior of GGW below cutoff remains unknown. This work presents a discussion of both below and above cutoff propagation characteristics of GGW, and introduces a simple model that explains the observed GGW behavior and establishes well its propagation characteristics. Two TRL calibration kits have been manufactured, and the measurements have good agreement with the proposed analysis model results.

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This dissertation examines the emergence and development of sound installation art, an under-recognized tradition that has developed between music, architecture, and media art practices since the late 1950s. Unlike many musical works, which are concerned with organizing sounds in time, sound installations organize sounds in space; they thus necessitate new theoretical and analytical models that take into consideration the spatial situated-ness of sound. Existing discourses on “spatial sound” privilege technical descriptions of sound localization. By contrast, this dissertation examines the ways in which concepts of space are socially, culturally, and politically construed, and how spatially-organized sound works reflect and resist these different constructions. Using an interdisciplinary methodology of critical spatial analysis and critical studies in music, this dissertation explores such topics as: conceptions of acoustic space in postwar Western art music, architecture, and media theory; the development of sound installation art in relation to philosophies of everyday life and social space; the historical links between musical performance, conceptual art, and sound sculpture; the body as a site for sound installations; and sonicspatial strategies that confront politics of race and gender. Through these different investigations, this dissertation proposes an “ontopological” model for considering sound: a critical model of analysis and reception that privileges an understanding of sound in relation to ontologies of space and place.

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A 20 minute sound walk produced by Emily DeDakis, Isobel Anderson and Garrett Carr. £7000 funding award for this project came from the BBC Legacy Grants 2015. I was CI on this application.

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Ultrasound absorption spectra of four 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide were determined as a function of the alkyl chain length on the cation from 1-propyl- to 1-hexyl- from 293.15 to 323.15 K at ambient pressure. Herein, the ultrasound absorption measurements were carried out using a standard pulse technique within a frequency range from 10 to 300 MHz. Additionally the speed of sound, density and viscosity have been measured. The presence of strong dissipative processes during the ultrasound wave propagation was found experimentally, i.e. relaxation processes in the megahertz range were observed for all compounds over the whole temperature range. The relaxation spectra (both relaxation amplitude and relaxation frequency) were shown to be dependent on the alkyl side chain length of the 1-alkyl-3-methylimidazolium ring. In most cases, a single Debye model described the absorption spectra very well. However, a comparison of the determined spectra with the spectra of a few other imidazolium-based ionic liquids reported in the literature (in part recalculated in this work) shows that the complexity of the spectra increases rapidly with the elongation of the alkyl chain length on the cation. This complexity indicates that both the volume viscosity and the shear viscosity are involved in relaxation processes even in relatively low frequency ranges. As a consequence, the sound velocity dispersion is present at relatively low megahertz frequencies.

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We propose a new selective multi-carrier index keying in orthogonal frequency division multiplexing (OFDM) systems that opportunistically modulate both a small subset of sub-carriers and their indices. Particularly, we investigate the performance enhancement in two cases of error propagation sensitive and compromised deviceto-device (D2D) communications. For the performance evaluation, we focus on analyzing the error propagation probability (EPP) introducing the exact and upper bound expressions on the detection error probability, in the presence of both imperfect and perfect detection of active multi-carrier indices. The average EPP results in closedform are generalized for various fading distribution using the moment generating function, and our numerical results clearly show that the proposed approach is desirable for reliable and energy-efficient D2D applications.

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Aims/hypothesis: We aimed to determine whether plasma lipoproteins, after leakage into the retina and modification by glycation and oxidation, contribute to the development of diabetic retinopathy in a mouse model of type 1 diabetes.

Methods: To simulate permeation of plasma lipoproteins intoretinal tissues, streptozotocin-induced mouse models of diabetes and non-diabetic mice were challenged with intravitreal injection of human ‘highly-oxidised glycated’ low-density lipoprotein (HOG-LDL), native- (N-) LDL, or the vehicle PBS.Retinal histology, electroretinography (ERG) and biochemical markers were assessed over the subsequent 14 days.

Results: Intravitreal administration of N-LDL and PBS had noeffect on retinal structure or function in either diabetic or non-diabetic animals. In non-diabetic mice, HOG-LDL elicited a transient inflammatory response without altering retinal function,but in diabetic mice it caused severe, progressive retinal injury, with abnormal morphology, ERG changes, vascular leakage, vascular endothelial growth factor overexpression, gliosis, endoplasmic reticulum stress, and propensity to apoptosis.

Conclusions/interpretation: Diabetes confers susceptibility to retinal injury imposed by intravitreal injection of modified LDL. The data add to the existing evidence that extravasated, modified plasma lipoproteins contribute to the propagation of diabetic retinopathy. Intravitreal delivery of HOG-LDL simulates a stress known to be present, in addition to hyperglycaemia, in human diabetic retinopathy once blood retinal barriers are compromised.

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This thesis explores the possibilities of spatial hearing in relation to sound perception, and presents three acousmatic compositions based on a musical aesthetic that emphasizes this relation in musical discourse. The first important characteristic of these compositions is the exclusive use of sine waves and other time invariant sound signals. Even though these types of sound signals present no variations in time, it is possible to perceive pitch, loudness, and tone color variations as soon as they move in space due to acoustic processes involved in spatial hearing. To emphasize the perception of such variations, this thesis proposes to divide a tone in multiple sound units and spread them in space using several loudspeakers arranged around the listener. In addition to the perception of sound attribute variations, it is also possible to create rhythm and texture variations that depend on how sound units are arranged in space. This strategy permits to overcome the so called "sound surrogacy" implicit in acousmatic music, as it is possible to establish cause-effect relations between sound movement and the perception of sound attribute, rhythm, and texture variations. Another important consequence of using sound fragmentation together with sound spatialization is the possibility to produce diffuse sound fields independently from the levels of reverberation of the room, and to create sound spaces with a certain spatial depth without using any kind of artificial sound delay or reverberation.

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Sound localization can be defined as the ability to identify the position of an input sound source and is considered a powerful aspect of mammalian perception. For low frequency sounds, i.e., in the range 270 Hz-1.5 KHz, the mammalian auditory pathway achieves this by extracting the Interaural Time Difference between sound signals being received by the left and right ear. This processing is performed in a region of the brain known as the Medial Superior Olive (MSO). This paper presents a Spiking Neural Network (SNN) based model of the MSO. The network model is trained using the Spike Timing Dependent Plasticity learning rule using experimentally observed Head Related Transfer Function data in an adult domestic cat. The results presented demonstrate how the proposed SNN model is able to perform sound localization with an accuracy of 91.82% when an error tolerance of +/-10 degrees is used. For angular resolutions down to 2.5 degrees , it will be demonstrated how software based simulations of the model incur significant computation times. The paper thus also addresses preliminary implementation on a Field Programmable Gate Array based hardware platform to accelerate system performance.

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In this paper, a spiking neural network (SNN) architecture to simulate the sound localization ability of the mammalian auditory pathways using the interaural intensity difference cue is presented. The lateral superior olive was the inspiration for the architecture, which required the integration of an auditory periphery (cochlea) model and a model of the medial nucleus of the trapezoid body. The SNN uses leaky integrateand-fire excitatory and inhibitory spiking neurons, facilitating synapses and receptive fields. Experimentally derived headrelated transfer function (HRTF) acoustical data from adult domestic cats were employed to train and validate the localization ability of the architecture, training used the supervised learning algorithm called the remote supervision method to determine the azimuthal angles. The experimental results demonstrate that the architecture performs best when it is localizing high-frequency sound data in agreement with the biology, and also shows a high degree of robustness when the HRTF acoustical data is corrupted by noise.

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A moving image work based on research with neurologists and audiologists, collectors and archivists. The film gives voice to the idea that every surface, in particular parts of our anatomy, is potentially inscribed with an unheard sound or echoes of voices from the past. The soundtrack’s musical composition is interlaced with a voice-over which draws on Rainer Maria Rilke’s text 'Primal Sound', where he reflects on the possibility of playing the coronal suture of a skull with a phonograph needle. The film uses microscopic photography, scanning electron microscopy, and sounds of otoacoustic emissions to uncover haunting aural bonescapes. The voiceovers too are recorded using old sound technology as a filter - writing and over-writing of wax cylinder to create unexpected scratches, glitches, loops and echoes. Exhibitions: shown as multi-channel sound/film installation AV festival (Newcastle 2010); solo exhibition at Wellcome Collection (London 2010-11); group exhibition ‘Samsung Art+ Prize’ BFI Southbank (London 2012); group exhibition ‘Transcendence’, Gertrude Contemporary, Melbourne (2014); solo exhibition as part of the International Rotterdam Film Festival (2013); group exhibition ‘The Sight of Sound’, Deutsche Bank VIP Lounge, Frieze Art Fair, NY (2012). Screenings: mini-retrospective at the Lincoln Centre, NY, as part of the New York Film Festival (2013); Jarman Award Tour screenings (2012, venues included Whitechapel Gallery, London; FACT, Liverpool; CCA, Glasgow; The Northern Charter in partnership with CIRCA projects; Nottingham Contemporary, Nottingham; Watershed, Bristol; Duke of York Cinema, Brighton), Whitechapel Gallery, London; FACT, Liverpool; CCA, Glasgow; The Northern Charter in partnership with CIRCA projects, Newcastle (special Q&A Aura Satz with Rebecca Shatwell, director of AV festival); Nottingham Contemporary, Nottingham; Watershed, Bristol; Duke of York Cinema, Brighton; Mini-retrospective at Tate Britain (London 2014); Mini-retrospective screening, DIM Cinema, The Cinematheque (Vancouver 2015); Mini-retrospective at Whitechapel Gallery (London 2016). Publications: ‘Sound Seam’ booklet with contributions by Steven Connor and Tom McCarthy (2010).

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Dissertação mest., Engenharia Biológica, Universidade do Algarve, 2009

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Tese de doutoramento, Engenharia Electrónica e Telecomunicações (Processamento de Sinal), Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014