Underwater acoustic recordings of six Floating Production Storage and Offloading (FPSO) vessels moored off Western Australia are presented. Monopole source spectra were computed for use in environmental impact assessments of underwater noise. Given that operations on the FPSOs varied over the period of recording, and were sometimes unknown, the authors present a statistical approach to noise level estimation. No significant or consistent aspect dependence was found for the six FPSOs. Noise levels did not scale with FPSO size or power. The 5th, 50th (median), and 95th percentile source levels (broadband, 20 to 2500 Hz) were 188, 181, and 173 dB re 1 μPa @ 1 m, respectively.

Underwater passive acoustic recordings in the Southern and Indian Oceans off Australia from 2002 to 2016 have regularly captured a tonal signal of about 10 s duration at 22–28 Hz with a symmetrical bell-shaped envelope. The sound is often accompanied by short, higher frequency downsweeps and repeated at irregular intervals varying from 120 to 200 s. It is termed the “spot” call according to its appearance in spectrograms of long-time averaging. Although similar to the first part of an Antarctic blue whale Z-call, evidence suggests the call is produced by another great whale, with the source as yet not identified.

Similar to geophysical and anthropogenic noise, biological contributions to soundscapes vary considerably in frequency, time, and intensity. Fish choruses are a perfect example, contributing significantly to marine biological noise and are used here as an analogue for variations in soundscapes. Their species-characteristic signals vary thus, so do their choruses, which can raise ambient noise levels by up to tens of decibels, for prolonged periods. Multi-species choruses can occur, with varying degrees of temporal and frequency partitioning, or none at all. Australian datasets of underwater noise have been acquired for nearly two decades and multiple fish calling patterns have been detected. Detecting, delineating, and understanding these patterns is non-trivial and a metric relating their contribution to the soundscape with biodiversity or habitat would be an invaluable tool. In recent years, several acoustic indices have been derived, proving useful in the terrestrial domain. Investigation of their application in marine environmental studies has also begun. However, such a plethora of widely varying sources and changing patterns can affect acoustic indices. This paper describes a simple and automatic suite of tools to help identify signals of a wide range of time patterns which are potentially underrepresented or missed by acoustic complexity or biodiversity indices.

Sound emissions from impact pile driving of raked piles present a significant azimuthal dependence in the radiated sound field due to the non-axisymmetric orientation of the pile. In this work the sound radiation from raked piles is modeled using a finite element method (FEM) model of the pile and near-field region. The near-field model of the sound field is then used as input into a normal mode model to predict the sound radiation in the far-field. The azimuthal dependence of the radiated sound field is shown to be accurately predicted using an equivalent axisymmetric FEM model of the pile configuration, thus negating the need to construct a fully three-dimensional model (3D) of the raked pile. This is achieved by matching the radiated field from the equivalent axisymmetric pile model to a vertical array of phased point sources, and then horizontally offsetting the source locations to match the incline of the raked pile. The resulting sound field closely matches the numerical predictions from a fully 3D FEM model of the raked pile. The results of numerical modeling are compared to corresponding acoustic measurements taken on the North West shelf of Western Australia.

The marine soundscape, whether in coastal areas or the deepest ocean, in the tropics or at the poles, contains a myriad of sounds. Sounds may be grouped by their origin into geophony (e.g., wind, precipitation, waves, earthquakes, volcanoes, and ice), biophony (e.g., invertebrates, fishes, and marine mammals), and anthropophony (e.g., port construction, mineral and hydrocarbon exploration and production, renewable energy installation, and shipping). This chapter gives a brief overview of the geophony and biophony, and then focuses on the anthropophony. The sounds of boats and ships of various types, marine seismic surveys, drilling, dredging, pile driving, windfarms, geotechnical site investigations, sonars, echosounders, explosions, and acoustic mitigation devices are presented, along with their characteristic source levels and spectra. Approaches to modeling, in particular, the sounds emitted by ships, seismic airguns, and pile driving are discussed.