Active sonar performance modelling for Doppler-sensitive pulses

Accurate sonar performance modelling is essential to predict likely detection ranges that can be obtained by employing active anti-submarine warfare sonars. Reverberation forms an important source of interference for active sonar performance, the effects of which can be diminished by using Doppler-sensitive pulses. Therefore, it is of importance...

Report on Task 4 of project "SVOW OGP JIP airgun measurements: reporting

Measurements of sound emitted from airguns and airgun clusters are described. Measurements were made in 2007 and 2009-2010 in fjord environments in Norway and for various airgun types, chamber pressures, operating depths and airgun volumes. For each combination of these parameters, a sequence of up to 50 shots was performed, resulting in a few...

Characterization of the acoustic output of single marine-seismic airguns and clusters: The Svein Vaage dataset

The acoustical output of marine-seismic airguns is determined from recordings of the sound pressure made on hydrophones suspended below a floating barge from which the airguns are also deployed. The signals from multiple types of airguns are considered and each type is operated over a range of deployment depths and chamber pressures. The...

Environment dependent transition frequencies for RAM and Bellhop

Passive-sonar-performance modelling requires the accurate estimation of the acoustic field for a broad range of frequencies in various environments. In this paper, we assess the suitability of a Gaussian Beam (Bellhop) and Parabolic Equation model (RAM), whereby we focus primarily on computational efficiency. For Parabolic Equation (PE) models...

Modeling Acoustical Pressure and Particle Acceleration Close to Marine Seismic Airguns and Airgun Arrays

Comparisons are made of sound pressure and particle acceleration predicted by two methods in the vicinity of two arrays of marine-seismic airguns. Data describing the array properties and the environmental conditions are taken from test cases designed to facilitate intermodel comparison.The two propagation approaches, one based on method of...

Vector sensors and acoustic calibration procedures

The measurement of underwater sound for the purpose of environmental impact studies usually only involves the measurement of the sound pressure by hydrophones. Sea mammals are sensitive to sound pressure in water like land mammals are for sound pressure in air. However, some species of fish and invertebrates are also sensitive and responsive to...

Modelling noise from wind, rain and distant shipping in scenarios of varying complexity

Passive sonars attempt to detect sound radiated by vessels of interest. This detection takes place against a background of noise, with important sources of noise including distant shipping, rain falling on the sea surface and breaking waves and bursting bubbles associated with sea-surface waves. The estimation of these noises is therefore an...

Passive array gain in shallow water

Detecting sound in the ocean is greatly improved by hydrophone array processing. Until recently, operating large arrays required cumbersome data acquisition systems and processing computers. Thanks to miniaturisation of electronics and improvements in computing power, array size is now limited by practicalities of deploying large physical...

Modelling propagation of sound emitted by mini-airguns

A modelling approach is described in which time-domain underwater-acoustic source functions are generated using a model that predicts the motion of air-bubbles generated by mini-airguns operated at various pressures. These time-series are Fourier-transformed to produce frequency-domain descriptions of the source. These are combined with complex...

Development of a wideband underwater acoustic modulation providing quality-of-service support

There is a growing interest in the use of untethered underwater vehicles. These vehicles require robust and error-free underwater communication for transmission of mission-critical data. In contrast, the requirements for sensor payloads are often less stringent. Depending on the type of data, different Quality-ofService (QoS) demands can be...

Changes in 63Hz third-octave band sound levels over 42 months recorded at four deep-ocean observatories

The growing scientific and societal concerns about the effects of underwater sound on marine ecosystems have been recently recognised through the introduction of several international initiatives, like the International Quiet Ocean Experiment, aimed at measuring the environmental impact of ocean noise on large spatial and temporal scales. From a...