Underwater sound mapping is increasingly being used as a tool for monitoring and managing noise pollution from shipping in the marine environment. Sound maps typically rely on tracking data from the Automated Information System (AIS), but information available from AIS is limited and not easily related to vessel noise emissions. Thus, robust sound mapping tools not only require accurate models for estimating source levels for large numbers of marine vessels, but also an objective assessment of their uncertainties. As part of the Joint Monitoring Programme for Ambient Noise in the North Sea (JOMOPANS) project, a widely used reference spectrum model (RANDI 3.1) was validated against statistics of monopole ship source level measurements from the Vancouver Fraser Port Authority-led Enhancing Cetacean Habitat and Observation (ECHO) Program. These validation comparisons resulted in a new reference spectrum model (the JOMOPANS-ECHO source level model) that retains the power-law dependence on speed and length but incorporates class-specific reference speeds and new spectrum coefficients. The new reference spectrum model calculates the ship source level spectrum, in decidecade bands, as a function of frequency, speed, length, and AIS ship type. The statistical uncertainty (standard deviation of the deviation between model and measurement) in the predicted source level spectra of the new model is estimated to be 6 dB.

Fish species and aquatic invertebrates are sensitive to underwater sound particle motion. Studies on the impact of sound on marine life would benefit from sound particle motion models. Benchmark cases and solutions are proposed for the selection and verification of appropriate models. These include a range-independent environment, with and without shear in the sediment, and a range-dependent environment, without sediment shear. Analysis of the acoustic impedance illustrates that sound particle velocity can be directly estimated from the sound pressure field in shallow water scenarios, except at distances within one wavelength of the source, or a few water depths at frequencies where the wavelength exceeds the water depth.

The Q7 is the second offshore wind farm in the Dutch sector of the North Sea and, at 23 km off the Dutch coast, the world's first to be located outside the 12‐mile limit. To support the wind turbines, monopiles (54 metres long steel pipes with a diameter of 4 metres) are hammered into the seabed using a pile‐driver. The underwater radiated noise during the impulsive hammering of 9 out of 61 monopiles was monitored. Although there is a wide concern about the impact of piling noise on the marine life in the area, there are no criteria for the maximum acceptable noise levels. A quantitative comparison of the results of various studies in which the underwater noise from pile driving has been measured and reported is difficult, due to the lack of standardization in the level definitions and data processing. The Q7 data have been analyzed in terms of a broadband sound exposure level, peak pressure and pulse duration and a 1/3‐octave band frequency spectrum of the sound pressure at different hydrophone locations, for each hammer stroke that has been recorded. The results are discussed in relation to the stroke energy and the hydrophone distance and depth.

Bubble curtains are widely used to protect marine life from exposure to harmful noise during offshore pile driving. However, operating a bubble curtain is costly and compliance with government noise regulations remains a challenge. It is therefore important to optimise the acoustic effect of the available compressed air. An interesting approach to achieving this is to split the air flow rate into two separate bubble curtains, rather than one single bubble curtain. This concept is tested both experimentally and numerically in this paper. The experiments and the model show the expected increase in performance of the supplied compressed air when it is split between two manifolds. An increased insertion loss of up to 11 dB is measured. This increase in performance is possibly due to the fact that the reflective properties of the bubble curtains are maintained even when the air flow rate is halved. In effect, by splitting the air flow between two manifolds, a second acoustic barrier is added. Additionally, the variations in the bubble curtain performance between individual measurements are shown to be largely caused by temporal variations in the air distribution within the curtain. The applicability of equivalent fluid models for bubble curtains is discussed, and it is shown that accounting for a gap in the bubble curtain, close to the manifold where the bubble curtain is not yet fully developed, results in better agreement between the modelled and the measured values of the insertion loss.

Standardizing the process for measuring underwater sound generated by ships in shallow waters is a complex challenge currently under development. Recent progress has enabled the development of analytical formulations to represent propagation conditions underwater using propagation loss (PL) approximations, which are employed to derive the source level (SL) from ship sound pressure level (SPL) measurements. Underwater radiated noise (URN) tests conducted in the SATURN project enabled a detailed evaluation of the seabed critical angle (SCA) method, recommended by an early draft of the ongoing ISO 17208-3 standard, identifying a general underestimation of SL above ∼500 Hz compared to measurements under equivalent operating conditions in deep water, as described by ISO 17208-1. This article presents an alternative smoothed semi-coherent image (SSCI) method for calculating PL (and hence SL) and assesses the method's performance through analytical and empirical scenarios (including recordings of three different instrumentation deployment strategies at four distinct depths and four test distances). The SSCI method enhances accuracy over a broad frequency range while maintaining the general robustness, with a formulation that also seeks to preserve the simplicity of the SCA approach.