The aim of this work was to compare the stroke kinematics and race times of the freestyle final races at the 13th FINA World Championships between: (i) the three medalists versus the last three finalists; (ii) males versus female swimmers; (iii) all events in each gender. Data was collected from the champioships official web site. There were no significant differences in the stroke kinematics neither in the race times between medallists and non-medallists. There were significant effects in the stroke kinematics and race times according to race event. There were significant effects in the stroke kinematics and race times according to swimmers gender. It seems there are different tactics and biomechanical strategies according to gender and swimming event.

The aim of this work was to compare the stroke kinematics and race times of the freestyle final races at the 13th FINA World Championships between: (i) the three medalists versus the last three finalists; (ii) males versus female swimmers; (iii) all events in each gender. Data was collected from the champioships official web site. There were no significant differences in the stroke kinematics neither in the race times between medallists and non-medallists. There were significant effects in the stroke kinematics and race times according to race event. There were significant effects in the stroke kinematics and race times according to swimmers gender. It seems there are different tactics and biomechanical strategies according to gender and swimming event.

There is significant evidence that the low-frequency mean acoustic noise pressure level in the ocean has been constantly increasing in the last decades. The main noise sources responsible for this increase were identified as ship traffic, offshore construction and oil & gas surveying. The Portuguese Navy funded SUBECO project aims at deploying a network of multiparametric offshore buoys for environmental and acoustic monitoring. A preferred location for the individual buoys is within or close by the ship traffic separation lanes along the west coast of Portugal. It is therefore expected that the received acoustic field will be dominated by shipping noise as a mixture of both short and long range ships. Most ships will have an AIS so their position may be known at all times. One of the objectives of this network is to use the recorded sound to infer and calibrate model predicted noise in a wider area. This work proposes a relatively simple technique for estimating the radiated noise level of ship tracks within acoustic reach of a single (or a small number of closely localized) hydrophone(s). It is expected that the data constrained predicted field with the estimated source levels will provide a better fit to the actual wide area acoustic field. This work is a contribution to fulfill the requirements of Portugal to the European Union Marine Strategy Framework Directive (MSFD) aiming at a good environmental status.

The vision underlying the Widely scalable Mobile Underwater Sonar Technology (WiMUST) project is that of developing advanced cooperative and networked control / navigation systems to enable a large number (tenths) of marine robots towing small acoustic arrays to act as a coordinated team for seismic sub-bottom imaging. The space-time coherent processing of bottom returns requires the ensemble of short acoustic arrays to be seen as a single spatially distributed sensor array. Since the vehicles are free to move along range, cross-range and depth the resulting distributed sensor array may take, at least conceptually, any spatial shape. With array shape freedom comes the question of which is the most suitable (or optimal) array geometry for sub-bottom imaging and inversion. The answer to this question hinges, among others, on the definition of performance of a seismic sub-bottom profiling system. Determining the optimal sensor array geometry is clearly a ill-posed problem, since the optimal geometry is itself bottom dependent, and there is no such environment as "one size fits all". This work addresses several criteria for sub-bottom profiling system performance including gain, resolution and probability of detection. Two physical models will be tested: one based on acoustic wave reflection used in traditional seismic imaging, and another normally used in matched-field bottom properties estimation, that includes propagation and refraction. Simulations to support the theoretical developments and algorithms were obtained on a scenario inspired in a real environment off the coast of Peljesac (Croatia).

There at least two major potential consequences of deep sea mining: sediment plumes and energy input into the ocean. One of the major forms of energy input is ocean noise generated by the mining process. Project TRIDENT was set up under the Horizon Europe framework of the European Union, with the aim of contributing to a sustainable exploitation of seabed mineral resources, by developing a reliable, transparent and cost-effective system for prediction and continuous environmental impact monitoring of exploration and exploitation activities in the deep sea. Among the parameters monitored under TRIDENT there is ocean sound by means of in-situ, middle field and far-field fixed water column acoustic recorders and moving acoustic gliders. The area chosen for TRIDENT activity and system demonstration is the Tropic seamount, located to the south of Canary Islands. This paper sets up the modelling tools to determine to which extent the noise generated by a continuous mining activity on top of the Tropic seamount couples into the sound channel and propagates to the surrounding area. The difference between the measured (or modelled) ocean sound with and without mining activity is usually called excess noise level and is instrumental for developing indicators of environmental impact to sensitive species within acoustic range of the mining site.

Economic globalization and the continuous search for food, energy and raw materials led to an estimated 3 dB/decade increase of ocean noise intensity. Determining the level of anthropogenic noise, the so-called excess noise, and building identifiable meaningful indicators for supporting marine management policies currently requires extensive observation data and computer modeling. For modeling purposes, in this study, anthropogenic noise was reduced to shipping traffic drawn from Automatic Identification System data, and environmental sound was attributed to surface wind only. Data-model comparison allowed introducing a methodology for simple model calibration and estimate excess noise. This methodology was tested on acoustic recordings performed in June 2018 at three locations to the southwest of Faial-Pico Islands in the Azores archipelago. The results show that field-calibrated excess noise sound maps are in line with the shipping distribution in the area, revealing a number of potentially marine life-threatening hotspots. Excess noise addresses the need for a quantifiable measure of ocean noise only and therefore offers a basis for building suitable continuous anthropogenic noise pollution indicators.

The Island of Cabo Frio is at the tip of the Cabo Frio cape, a landmark of the Brazilian coast situated 23 degrees south, between the tropical ocean and the southern temperate region. This cape is subject to, often strong, NE winds developing a significant upwelling phenomenon on its southward . Between the island and the mainland there is bay relatively protected from the southern ocean by a rocky shore that has only a narrow entrance, through which extremely cold water enters when upwelling occurs. For more than one year continuous sound recording has been performed near the rock shore (Xavier et al., 2018). From January 14 to 18, 2019, an experiment named BIOCOM19, involving acoustic transmissions across the bay was carried out. Together with other instrumentation an acoustic vector sensor was also installed near the shore with the objective of recording particle velocity. It is now well known that a large number of organisms are sensitive to particle motion, which differentiates itself from sound pressure, specially near acoustically hard surfaces or at close distance from acoustic sources. The recorder itself is based on a dual tri-axial accelerometer combined with an hydrophone (Mantouka et al., 2017) and was primarily developed for seismic imaging from on board autonomous vehicles (Santos et al., 2017 and Felisberto et al., 2019). During BIOCOM19 the recorder was attached to a rectangular pod positioned at about 8 m from the rock wall and at 7m depth. The recorded data covers two full days and includes additional acoustic data along the water column and other environmental information such as temperature profiles both at the receiver site and along the transmission path across the bay. The data processed so far shows that together with sound pressure particle velocity is clearly sensitive to the biological signature identifiable in the area. A daily pattern can be observed between 1.5 and 5 kHz, during the periods without acoustic transmissions, as coming from the rocky wall. Particle motion is extremely difficult to interpret but seems to show a similar pattern, at least for the accelerometer that is placed towards the shore. This study supports the development of tools to identify and classify several bioacoustic signatures from benthic community.

This paper describes the lessons learned from the experiment BIOCOM’19 carried out in January 2019, in a shallow water bay off the island of Cabo Frio (RJ, Brazil). A dual accelerometer vector sensor hydrophone was deployed for two days, near a rocky shore covered with a significant benthic fauna. The results show that the frequency band above approximately 1.5 kHz is mostly associated with invertebrate biological noise and that the acoustic and the particle motion fields have a similar behavior, following the usual dawn-dusk activity pattern, and a coherent directivity content. At low frequencies, below 300 Hz, the acoustic pressure and the particle acceleration fields have significantly different spectral content along time. Many of these differences are due to anthropogenic noise sources related with nearby boating activity, while during quiet periods, they may be attributed to the biological activity from the rocky shore