Modelling underwater acoustic noise as a tool for coastal management

Dissertação de Mestrado, Gestão da Água e da Costa, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2009

Analysis of underwater acoustic data via 3-D segmentation

The analysis of seabed structure is important in a wide variety of scientific and industrial applications. In this paper, underwater acoustic data produced by bottom-penetrating sonar (Topas) are analyzed using unsupervised volumetric segmentation, based on a three dimensional Gibbs-Markov model. The result is a concise and accurate description of the seabed, in which key structures are emphasized. This description is also very well suited to further operations, such as the enhancement and automatic recognition of important structures. Experimental results demonstrating the effectiveness of this approach are shown, using Topas data gathered in the North Sea off Horten, Norway.

Seismo-acoustic ray model benchmarking against experimental tank data

Acoustic predictions of the recently developed TRACEO ray model, which accounts for bottom shear properties, are benchmarked against tank experimental data from the EPEE-1 and EPEE-2 (Elastic Parabolic Equation Experiment) experiments. Both experiments are representative of signal propagation in a Pekeris-like shallow-water waveguide over a non-flat isotropic elastic bottom, where significant interaction of the signal with the bottom can be expected. The benchmarks show, in particular, that the ray model can be as accurate as a parabolic approximation model benchmarked in similar conditions. The results of benchmarking are important, on one side, as a preliminary experimental validation of the model and, on the other side, demonstrates the reliability of the ray approach for seismo-acoustic applications. (C) 2012 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4734236]

Rate adaptation for wireless video streaming based on error statistics

This paper presents a new rate-control algorithm for live video streaming over wireless IP networks, which is based on selective frame discarding. In the proposed mechanism excess 'P' frames are dropped from the output queue at the sender using a congestion estimate based on packet loss statistics obtained from RTCP feedback and from the Data Link (DL) layer. The performance of the algorithm is evaluated through computer simulation. This paper also presents a characterisation of packet losses owing to transmission errors and congestion, which can help in choosing appropriate strategies to maximise the video quality experienced by the end user. Copyright © 2007 Inderscience Enterprises Ltd.

Peer-to-peer video streaming

The Internet as a video distribution medium has seen a tremendous growth in recent years. Currently, the transmission of major live events and TV channels over the Internet can easily reach hundreds or millions of users trying to receive the same content using very distinct receiver terminals, placing both scalability and heterogeneity challenges to content and network providers. In private and well-managed Internet Protocol (IP) networks these types of distributions are supported by specially designed architectures, complemented with IP Multicast protocols and Quality of Service (QoS) solutions. However, the Best-Effort and Unicast nature of the Internet requires the introduction of a new set of protocols and related architectures to support the distribution of these contents. In the field of file and non-real time content distributions this has led to the creation and development of several Peer-to-Peer protocols that have experienced great success in recent years. This chapter presents the current research and developments in Peer-to-Peer video streaming over the Internet. A special focus is made on peer protocols, associated architectures and video coding techniques. The authors also review and describe current Peer-to-Peer streaming solutions. © 2013, IGI Global.

Acoustic oceanographic buoy telemetry system: an ‘advanced’ sonobuoy that meets acoustic rapid environmental assessment requirements

The Acoustic Oceanographic Buoy (AOB) Telemetry System has been designed to meet acoustic rapid environmental assessment requirements. It uses a standard institute of Electrical and Electronics Engineers 802.11 wireless local area network (WLAN) to integrate the air radio network (RaN) and a hydrophone array and acoustic source to integrate the underwater acoustic network (AcN). It offers advantages including local data storage, dedicated signal processing, and global positioning system (GPS) timing and localization. The AOB can also be integrated with other similar systems, due to its WLAN transceivers, to form a flexible network and perform on-line high speed data transmissions. The AOB is a reusable system that requires less maintenance and can also work as a salt-water plug-and-play system at sea as it is designed to operate in free drifting mode. The AOB is also suitable for performing distributed digital signal processing tasks due to its digital signal processor facility.

On the applications of a compact autonomous acoustic recorder

A number of acoustic A compact acoustic recorder, primarily designed for underwater noise monitoring, is presented in this paper. The Self-Register Hydrophone has been used in several occasions during the past three years, in underwater noise monitoring activities. However, this kind of device also find application in other areas such as array processing and passive acoustic monitoring of marine mammals. An overview on the application of the Self-Register Hydrophone is given herein.

An autonomous system for ocean acoustic tomography

Vertical line arrays (VLA) are a widely used apparatus in underwater acoustics with applications in sonar prediction, underwater communications and acoustic tomography, among others. Recent developments in digital electronics and communications allow for off-the-shelf development of VLA systems, with a large number of embedded acoustic and non-acoustic sensors able to fulfill application requirements, as opposed to single or few receiver configurations available until only a few years ago. Very often, the flexibility in water column sampling is achieved by splitting the VLA into modules that can be assembled according to the application. Such systems can be deployed and recovered from small vessels with a shorthanded crew, and make it possible for research labs with reduced budgets and operational means (ships and manpower) to gain control over the whole development process, from data acquisition to post-processing.

Acoustic-oceanographic data fusion for prediction of oceanic acoustic elds

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