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Research funding was provided by the US Office of Naval Research and the Ministries of Defence of Norway, the Netherlands and France as well as the UK Natural Environmental Research Council. A key issue when investigating effects of anthropogenic noise on cetacean behavior is to identify the biological significance of the responses. Predator presence can be considered a natural high-level disturbance stimulus to which prey animals have evolved adaptive response strategies to reduce their risk of predation by altering behavior away from fitness-enhancing activities such as foraging. By contrasting the type and magnitude (duration, severity, consistency) of behavioral responses to anthropogenic noise and playback of killer whale (KW) sounds that simulated predator presence, this study aimed to provide a relative index of the disturbance level as an indication of the biological significance of responses to the anthropogenic stimulus. Using multi-sensor tags as well as visual observations of surface behavior of adult male sperm whales, we assessed a comprehensive range of behavioral metrics that could reduce individuals’ fitness if altered for a biologically relevant duration. Combining previously published results and new analyses, we showed that the responses to 1-2 kHz upsweep naval sonar and to KW playback were very similar, including horizontal avoidance, interruption of foraging or resting activities and an increase in social sound production. However, only KW playbacks elicited grouping behaviors, indicating that this social response component was specific to predator detection. Animals responded to a lesser extent to 6-7 kHz upsweep naval sonar, indicating weaker disturbance effects. Our study demonstrates the benefit of using anti-predator responses as a reference of disturbance when evaluating the relative impacts of anthropogenic stimuli, which can be of particular interest in studies of threatened species such as sperm whales. Publisher PDF

We designed and jointly optimized an integrated signal processing chain for detection and classification of long-range passive-acoustic underwater signals recorded by the global geophysical monitoring network of the Comprehensive Nuclear-Test-Ban Treaty Organization. Starting at the level of raw waveform data, a processing chain of signal detection, feature extraction, and signal classification was designed and jointly optimized to the task. Relevant waveform segments were in a first step identified by a generic, flexibly parameterized detection algorithm on a long-to short-term averages' ratio of the spectral energy. For representation, general-purpose sound processing features, with an added focus on spectral and cepstral features, were extracted from the detected segments. As classifiers, support vector machines with different kernel functions were employed alongside other baseline learning algorithms. The free parameters of the overall toolchain (i.e., trigger algorithm parameters and classifier hyperparameters) were jointly optimized in a cross-validation setting, either according to the cross-validation classification error or the cross-validation area under the receiver operating characteristic curve. Experiments demonstrate that our method outperforms machine learning algorithms task-tailored to a previous, human-expert-designed preprocessing chain. The presented approach can be adapted to a wide range of problems that can benefit from jointly optimizing parameters of preprocessing and classification algorithm. © 2016 IEEE.

Marine mammals may be negatively affected by anthropogenic noise. Behavioural response studies (BRS) aim to establish a relationship between noise exposure conditions (dose) from a potential stressor and associated behavioural responses of animals. A recent series of BRS have focused on the effects of naval sonar sounds on cetaceans. Here, we review the current state of understanding of naval sonar impact on marine mammals and highlight knowledge gaps and future research priorities. Many marine mammal species exhibit responses to naval sonar sounds. However, responses vary between and within individuals and populations, highlighting the importance of exposure context in modulating dose–response relationships. There is increasing support from both terrestrial and marine systems for the risk-disturbance hypothesis as an explanation for underlying response processes. This proposes that sonar sounds may be perceived by animals as a threat, evoking a response shaped by the underlying species-specific risk of predation and anti-predator strategy. An understanding of responses within both the dose–response and risk-disturbance frameworks may enhance our ability to predict responsiveness for unstudied species and populations. Many observed behavioural responses are energetically costly, but the way that these responses may lead to long-term individual and population-level impacts is poorly understood. Synthesis and applications. Behavioural response studies have greatly improved our understanding of the potential effects of naval sonar on marine mammals. Despite data gaps, we believe a dose-response approach within a risk-disturbance framework will enhance our ability to predict responsiveness for unstudied species and populations. We advocate for (1) regulatory frameworks to utilize peer-reviewed research findings when making predictions of impact, (2) regulatory frameworks to account for the inherent uncertainty in predictions of impact and (3) investment in monitoring programmes that are both directed by recent research and offer opportunities for validation of predictions at the individual and population level. © 2017 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Passive acoustic monitoring with widely-dispersed hydrophones has been suggested as a cost-effective method to monitor population densities of echolocating marine mammals. This requires an estimate of the area around each receiver over which vocalizations are detected - the "effective detection area" (EDA). In the absence of auxiliary measurements enabling estimation of the EDA, it can be modelled instead. Common simplifying model assumptions include approximating the spectrum of clicks by flat energy spectra, and neglecting the frequency-dependence of sound absorption within the click bandwidth (narrowband assumption), rendering the problem amenable to solution using the sonar equation. Here, it is investigated how these approximations affect the estimated EDA and their potential for biasing the estimated density. EDA was estimated using the passive sonar equation, and by applying detectors to simulated clicks injected into measurements of background noise. By comparing model predictions made using these two approaches for different spectral energy distributions of echolocation clicks, but identical click source energy level and detector settings, EDA differed by up to a factor of 2 for Blainville's beaked whales. Both methods predicted relative density bias due to narrowband assumptions ranged from 5% to more than 100%, depending on the species, detector settings, and noise conditions. © 2018 Acoustical Society of America.

Passive acoustic monitoring with widely-dispersed hydrophones has been suggested as a cost-effective method to monitor population densities of echolocating marine mammals. This requires an estimate of the area around each receiver over which vocalizations are detected - the "effective detection area" (EDA). In the absence of auxiliary measurements enabling estimation of the EDA, it can be modelled instead. Common simplifying model assumptions include approximating the spectrum of clicks by flat energy spectra, and neglecting the frequency-dependence of sound absorption within the click bandwidth (narrowband assumption), rendering the problem amenable to solution using the sonar equation. Here, it is investigated how these approximations affect the estimated EDA and their potential for biasing the estimated density. EDA was estimated using the passive sonar equation, and by applying detectors to simulated clicks injected into measurements of background noise. By comparing model predictions made using these two approaches for different spectral energy distributions of echolocation clicks, but identical click source energy level and detector settings, EDA differed by up to a factor of 2 for Blainville's beaked whales. Both methods predicted relative density bias due to narrowband assumptions ranged from 5% to more than 100%, depending on the species, detector settings, and noise conditions. © 2018 Acoustical Society of America.

Marine mammals may be negatively affected by anthropogenic noise. Behavioural response studies (BRS) aim to establish a relationship between noise exposure conditions (dose) from a potential stressor and associated behavioural responses of animals. A recent series of BRS have focused on the effects of naval sonar sounds on cetaceans. Here, we review the current state of understanding of naval sonar impact on marine mammals and highlight knowledge gaps and future research priorities. Many marine mammal species exhibit responses to naval sonar sounds. However, responses vary between and within individuals and populations, highlighting the importance of exposure context in modulating dose–response relationships. There is increasing support from both terrestrial and marine systems for the risk-disturbance hypothesis as an explanation for underlying response processes. This proposes that sonar sounds may be perceived by animals as a threat, evoking a response shaped by the underlying species-specific risk of predation and anti-predator strategy. An understanding of responses within both the dose–response and risk-disturbance frameworks may enhance our ability to predict responsiveness for unstudied species and populations. Many observed behavioural responses are energetically costly, but the way that these responses may lead to long-term individual and population-level impacts is poorly understood. Synthesis and applications. Behavioural response studies have greatly improved our understanding of the potential effects of naval sonar on marine mammals. Despite data gaps, we believe a dose-response approach within a risk-disturbance framework will enhance our ability to predict responsiveness for unstudied species and populations. We advocate for (1) regulatory frameworks to utilize peer-reviewed research findings when making predictions of impact, (2) regulatory frameworks to account for the inherent uncertainty in predictions of impact and (3) investment in monitoring programmes that are both directed by recent research and offer opportunities for validation of predictions at the individual and population level. © 2017 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Sound produced by marine pile driving activities poses a possible risk to marine life. The assessment and mitigation of this risk requires a precise prediction of the expected levels. An analytical approach to estimate the radiated sound exposure levels is presented, based on the axial symmetry of the problem, resulting in damped cylindrical spreading. The approach is verified against numerical results from the recently held COMPILE benchmark workshop and validated with data from three different wind farm construction sites in the North Sea. In addition, found to yield more accurate estimates of the sound exposure level than an empirical decay formula sometimes used to evaluate the impact of marine pile driving. © 2018 Acoustical Society of America.

The SOCAL project was funded by the US Navy Chief of Naval Operations Environmental Readiness Division and US Office of Naval Research. The 3S project was funded by the Norwegian Ministry of Defence, the US Office of Naval Research, the Netherlands Ministry of Defence and DGA French Ministry of Defence. The MOCHA project was funded by the US Office of Naval Research. Tyack received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. Minke whales are difficult to study and little information exists regarding their responses to anthropogenic sound. This study pools data from behavioural response studies off California and Norway. Data are derived from four tagged animals, of which one from each location was exposed to naval sonar signals. Statistical analyses were conducted using Mahalanobis distance to compare overall changes in parameters summarising dive behaviour, avoidance behaviour, and potential energetic costs of disturbance. Our quantitative analysis showed that both animals initiated avoidance behaviour, but responses were not associated with unusual dive behaviour. In one exposed animal the avoidance of the sonar source included a 5-fold increase in horizontal speed away from the source, implying a significant increase in metabolic rate. Despite the different environmental settings and exposure contexts, clear changes in behaviour were observed providing the first insights into the nature of responses to human noise for this wide-ranging species. Postprint

In this paper we present the NECSAVE system which allows the control of heterogeneous unmanned vehicles under challenging environments by a single human operator by providing it with the desired highlevel objectives. The described software stack takes care of decomposing the high-level objectives into assignable tasks and (re)distributing the workload among team members according to their announced capabilities and eventual failures. NECSAVE is robust to system failures by supporting decentralized planning and adapting allocation in face of platform losses. The system was validated in multiple field trials where NECSAVE was used for the coordination of heterogeneous vehicles under challenged communication environments, namely the sea using radio (at surface) and acoustic communications (underwater).

Acoustic underwater communication is an enabler for the use of autonomous underwater vehicles (AUVs). AUVs can operate in acoustically challenging environments, e.g., near offshore platforms and in harbours. To realize robust underwater communication in such environments, the propagation conditions need to be properly understood. In this paper, the performance of underwater acoustic communication in shallow water harbour environments is investigated. To perform our investigation, channel soundings (i.e., empirical channel impulse responses) captured in the Port of East-Vlissingen (The Netherlands) are employed. In particular, it is investigated how the increase of acoustic reverberation caused by reflections from physical structures in a harbour (e.g., quay walls, jetties, piers) affects the underwater acoustic communication performance. The empirical reverberation obtained from the channel soundings is compared with the modelled two-dimensional equivalent in order to make a distinction between bottom-surface paths and reflections from physical structures in the harbour. The collected channel soundings and their analysis are necessary for the development of novel modulation methods and provide useful input for an improved understanding of the acoustic propagation conditions in harbour environments. The findings in this paper can be used by future tools for autonomous underwater operations.

A concept for underwater machinery noise mitigation of future civil and military ships is the application of a common deck structure, supporting multiple machines, which is installed on resilient mounts on the ship's foundation structure. TNO is addressing the availability and testing of tools to be able to set realistic targets for the radiated noise signature and to verify future vessel designs against these targets. The TNO Assessment Model for Radiated Underwater Sound (AMRUS) is a semi-empirical prediction tool to predict separate contributions of different resiliently machinery noise sources to the underwater radiated noise at far field locations. It is a compilation of measured machinery source acceleration levels, mounting transfer and ship transfer functions, which are present in a large database. Until recently, the effect of resiliently mounted ('floating') deck structures on machinery noise transmission was not included in AMRUS. To be able to the support the complex design process of a floating deck, a formulation of the deck mount transfer function has been derived. For that purpose this formulation is split into the separate deck structure input and transfer mobilities, which can serve as acoustic indicators for a specific deck design during the specification, design and building phases. The formulation can be used to assess global design parameters of a deck in an early design phase, but can also serve as a base for finite element model results to determine the mount transfer function for a more detailed deck design. ANV; Cirrus Research Plc; Orion

Minke whales are difficult to study and little information exists regarding their responses to anthropogenic sound. This study pools data from behavioural response studies off California and Norway. Data are derived from four tagged animals, of which one from each location was exposed to naval sonar signals. Statistical analyses were conducted using Mahalanobis distance to compare overall changes in parameters summarising dive behaviour, avoidance behaviour, and potential energetic costs of disturbance. Our quantitative analysis showed that both animals initiated avoidance behaviour, but responses were not associated with unusual dive behaviour. In one exposed animal the avoidance of the sonar source included a 5-fold increase in horizontal speed away from the source, implying a significant increase in metabolic rate. Despite the different environmental settings and exposure contexts, clear changes in behaviour were observed providing the first insights into the nature of responses to human noise for this wide-ranging species.

Proper spatial sampling is critical for many applications. If the sampling criterion is not met, artifacts appear for example in images. Last year an iterative approach was presented using wave field extrapolation to interpolate spatially aliased signals. The main idea behind this approach is that after inverse wave field extrapolation the signal is concentrated in a small region with a high amplitude, while the aliasing artifacts are spread-out through the domain. Inverse wave field extrapolation focusses optimally at one depth, making the performance of the reconstruction depth dependent. Obviously the method can be repeated for several depths. This year we show an alternative approach using an imaging/inverse-imaging approach. The demonstration of this approach is extended to 2D-arrays where the sampling limitations are even more critical. Moreover we show in this paper that the interpolation approach is not limited to near-field data, but can also be used on far-field data (plane waves). The Radon transform can be used for plane waves to focus the data. The approach is demonstrated using modeled and measured data for linear and 2D arrays.

The ocean is nearly transparent to low frequency sound permitting the observation of distant events such as earthquakes or explosions at fully basin scales. For very low frequency the ocean acts as a shallow-water waveguide and lateral variability in bathymetry can lead to out-of-plane effects. In this paper, data from the International Monitoring System of the Comprehensive Test Ban Treaty Organization (CTBTO) is used to present two cases where robustly localized seismic events in locations clearly within the two-dimensional (2-D) shadow of a continent or large island generate T-phase signals that are received on a hydro-acoustic station. A fully three- dimensional parabolic equation model is used to demonstrate that lateral variability of the bathymetry can lead to diffraction, explaining both observations. The implications of this are that the CTBTO network has greater coverage than predicted by 2-D models and that inclusion of diffraction in future processing can improve the automatic global association of hydroacoustic events. © 2017 Acoustical Society of America.

In distributed and decentralized state estimation systems, fusion methods are employed to systematically combine multiple estimates of the state into a single, more accurate estimate. An often encountered problem in the fusion process relates to unknown common information that is shared by the estimates to be fused and is responsible for correlations. If the correlation structure is unknown to the fusion method, conservative strategies are typically pursued. As such, the parameterization introduced by the ellipsoidal intersection method has been a novel approach to describe unknown correlations, though suitable values for these parameters with proven consistency have not been identified yet. In this article, an extension of ellipsoidal intersection is proposed that guarantees consistent fusion results in the presence of unknown common information. The bound used by the novel approach corresponds to computing an outer ellipsoidal bound on the intersection of inverse covariance ellipsoids. As a major advantage of this inverse covariance intersection method, fusion results prove to be more accurate than those provided by the well-known covariance intersection method. © 2017 Elsevier Ltd

Decentralized data fusion is a challenging task. Either it is too difficult to maintain and track the information required to perform fusion optimally, or too much information is discarded to obtain informative fusion results. A well-known solution is Covariance Intersection, which may provide too conservative fusion results. A less conservative alternative is discussed in this paper, and generalizations are proposed in order to apply it to a wide class of fusion problems. The Inverse Covariance Intersection algorithm is about finding the maximum possible common information shared by the estimates to be fused. A bound on the possibly shared common information is derived and removed from the fusion result in order to guarantee consistency. It is shown that the conditions required for consistency can be significantly relaxed, and also other causes of correlations, such as common process noise, can be treated. © 2017 International Society of Information Fusion (ISIF). China Gezhouba Group No.3 Engineering Co., Ltd (CGGC); Energy China; et al.; Hangzhou Dianzi Univeristy; LIFT; SATPRO

This paper presents a method to realize an acoustic source for low frequencies with relatively small thickness. A honeycomb plate structure which is open on one side combines the radiating surface and the major part of the air cavity. The vibration of the plate is controlled with a decentralized feedback controller. The fundamental resonance caused by the mass of the plate and the compliance of the air cavity are controlled, as well as the first-order bending mode, while avoiding possible instabilities due to the fluid-structure interaction. The smooth and well defined frequency response enables robust feedforward control for further response equalization. The influence of different actuation principles on the overall system efficiency is compared.

Thecontributionofshippingnoisetothebackground noise in the seas can be estimated by shipping noise maps. Noise maps can be made by applying appropriate modeling tools for underwater sound propagation and ship source levels to information on the acoustic environment and on the ship traffic in the area of the map. The development of reliable source level models requires the availability of a variety of radiated noise data of ships. Therefore, full-scale radiated noise measurements were performed near ashippinglaneincoastalwatersoutofthePortofRotterdam.The results of the noise measurements are combined with information about the measured ships and their positions, derived from registered AIS data, and with propagation conditions to determine source levels. Criteria have been developed to select the data from which a reliable source level estimation can be obtained from individual ship passages at the busy shipping lanes. Source levels of different types of ships are compared.

In seismic surveys, reflected sounds from airguns are used under water to detect gas and oil below the sea floor. The airguns produce broadband high-amplitude impulsive sounds, which may cause temporary or permanent threshold shifts (TTS or PTS) in cetaceans. The magnitude of the threshold shifts and the hearing frequencies at which they occur depend on factors such as the received cumulative sound exposure level (SELcum), the number of exposures, and the frequency content of the sounds. To quantify TTS caused by airgun exposure and the subsequent hearing recovery, the hearing of a harbor porpoise was tested by means of a psychophysical technique. TTS was observed after exposure to 10 and 20 consecutive shots fired from two airguns simultaneously (SELcum: 188 and 191 dB re 1 μPa2s) with mean shot intervals of around 17 s. Although most of the airgun sounds' energy was below 1 kHz, statistically significant initial TTS1-4 (1-4 min after sound exposure stopped) of ∼4.4 dB occurred only at the hearing frequency 4 kHz, and not at lower hearing frequencies tested (0.5, 1, and 2 kHz). Recovery occurred within 12 min post-exposure. The study indicates that frequency-weighted SELcum is a good predictor for the low levels of TTS observed. © 2017 Acoustical Society of America.

This paper presents a method to realize an acoustic source for low frequencies with relatively small thickness. A honeycomb plate structure which is open on one side combines the radiating surface and the major part of the air cavity. The vibration of the plate is controlled with a decentralized feedback controller. The fundamental resonance caused by the mass of the plate and the compliance of the air cavity are controlled, as well as the first-order bending mode, while avoiding possible instabilities due to the fluid-structure interaction. The smooth and well defined frequency response enables robust feedforward control for further response equalization. The influence of different actuation principles on the overall system efficiency is compared.

Source localization using microphone arrays has now become common practice for many applications. Their application for long term monitoring of industrial noise nevertheless remains uncommon. Hence, in 2016 we deployed four microphone arrays near a large industrial area for a period of 12 months and explored the challenges involved. The difficult meteorological conditions leading to strongly varying attenuations, 3D refraction, and scattering turned out to be one of these major challenges. Changes in predicted source locations and estimated source power are quite often the result of abrupt changes in local weather conditions. Notwithstanding the careful weather monitoring, assumptions and hypotheses on the sources' temporal behavior and spectra combined with a statistical locator were still needed to obtain satisfactory results. Validation of the proposed approaches on a known source with stable noise emission over time is presented in the paper. © 2017 Institute of Noise Control Engineering. All rights reserved. Meetings and Exhibitions Hong Kong (MEHK)

In distributed and decentralized state estimation systems, fusion methods are employed to systematically combine multiple estimates of the state into a single, more accurate estimate. An often encountered problem in the fusion process relates to unknown common information that is shared by the estimates to be fused and is responsible for correlations. If the correlation structure is unknown to the fusion method, conservative strategies are typically pursued. As such, the parameterization introduced by the ellipsoidal intersection method has been a novel approach to describe unknown correlations, though suitable values for these parameters with proven consistency have not been identified yet. In this article, an extension of ellipsoidal intersection is proposed that guarantees consistent fusion results in the presence of unknown common information. The bound used by the novel approach corresponds to computing an outer ellipsoidal bound on the intersection of inverse covariance ellipsoids. As a major advantage of this inverse covariance intersection method, fusion results prove to be more accurate than those provided by the well-known covariance intersection method. © 2017 Elsevier Ltd

Proper spatial sampling is critical for many applications. If the sampling criterion is not met, artifacts appear for example in images. Last year an iterative approach was presented using wave field extrapolation to interpolate spatially aliased signals. The main idea behind this approach is that after inverse wave field extrapolation the signal is concentrated in a small region with a high amplitude, while the aliasing artifacts are spread-out through the domain. Inverse wave field extrapolation focusses optimally at one depth, making the performance of the reconstruction depth dependent. Obviously the method can be repeated for several depths. This year we show an alternative approach using an imaging/inverse-imaging approach. The demonstration of this approach is extended to 2D-arrays where the sampling limitations are even more critical. Moreover we show in this paper that the interpolation approach is not limited to near-field data, but can also be used on far-field data (plane waves). The Radon transform can be used for plane waves to focus the data. The approach is demonstrated using modeled and measured data for linear and 2D arrays.

Source localization using microphone arrays has now become common practice for many applications. Their application for long term monitoring of industrial noise nevertheless remains uncommon. Hence, in 2016 we deployed four microphone arrays near a large industrial area for a period of 12 months and explored the challenges involved. The difficult meteorological conditions leading to strongly varying attenuations, 3D refraction, and scattering turned out to be one of these major challenges. Changes in predicted source locations and estimated source power are quite often the result of abrupt changes in local weather conditions. Notwithstanding the careful weather monitoring, assumptions and hypotheses on the sources' temporal behavior and spectra combined with a statistical locator were still needed to obtain satisfactory results. Validation of the proposed approaches on a known source with stable noise emission over time is presented in the paper. © 2017 Institute of Noise Control Engineering. All rights reserved. Meetings and Exhibitions Hong Kong (MEHK)

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 identified. To maximize the bandwidth utilization of underwater communication links, a modulation that provides the possibility to have multiple QoS levels within a single transmission is introduced. This flexible modulation is labelled Multi-Stream Frequency-Repetition Spread Spectrum (MSFRSS) and provides configurable quality-of-service levels for distinct parts of the communicated message. Early channel replay simulations encourage future tests of MSFRSS in alternative configurations and environments

A concept for underwater machinery noise mitigation of future civil and military ships is the application of a common deck structure, supporting multiple machines, which is installed on resilient mounts on the ship's foundation structure. TNO is addressing the availability and testing of tools to be able to set realistic targets for the radiated noise signature and to verify future vessel designs against these targets. The TNO Assessment Model for Radiated Underwater Sound (AMRUS) is a semi-empirical prediction tool to predict separate contributions of different resiliently machinery noise sources to the underwater radiated noise at far field locations. It is a compilation of measured machinery source acceleration levels, mounting transfer and ship transfer functions, which are present in a large database. Until recently, the effect of resiliently mounted ('floating') deck structures on machinery noise transmission was not included in AMRUS. To be able to the support the complex design process of a floating deck, a formulation of the deck mount transfer function has been derived. For that purpose this formulation is split into the separate deck structure input and transfer mobilities, which can serve as acoustic indicators for a specific deck design during the specification, design and building phases. The formulation can be used to assess global design parameters of a deck in an early design phase, but can also serve as a base for finite element model results to determine the mount transfer function for a more detailed deck design. ANV; Cirrus Research Plc; Orion

Wegverkeer en machines buiten zijn belangrijke bronnen van geluid-hinder en slaapverstoring. Wat is de stand van zaken en wat draagt Nederland bij aan de aanscherping van Europese limieten?

Decentralized data fusion is a challenging task. Either it is too difficult to maintain and track the information required to perform fusion optimally, or too much information is discarded to obtain informative fusion results. A well-known solution is Covariance Intersection, which may provide too conservative fusion results. A less conservative alternative is discussed in this paper, and generalizations are proposed in order to apply it to a wide class of fusion problems. The Inverse Covariance Intersection algorithm is about finding the maximum possible common information shared by the estimates to be fused. A bound on the possibly shared common information is derived and removed from the fusion result in order to guarantee consistency. It is shown that the conditions required for consistency can be significantly relaxed, and also other causes of correlations, such as common process noise, can be treated. © 2017 International Society of Information Fusion (ISIF). China Gezhouba Group No.3 Engineering Co., Ltd (CGGC); Energy China; et al.; Hangzhou Dianzi Univeristy; LIFT; SATPRO

Wegverkeer en machines buiten zijn belangrijke bronnen van geluid-hinder en slaapverstoring. Wat is de stand van zaken en wat draagt Nederland bij aan de aanscherping van Europese limieten?

Exposure to underwater sound can cause permanent hearing loss and other physiological effects in marine animals. To reduce this risk, naval sonars are sometimes gradually increased in intensity at the start of transmission ('ramp-up'). Here, we conducted experiments in which tagged humpback whales were approached with a ship to test whether a sonar operation preceded by ramp-up reduced three risk indicators - maximum sound pressure level (SPLmax), cumulative sound exposure level (SELcum) and minimum source-whale range (Rmin) - compared with a sonar operation not preceded by ramp-up. Whales were subject to one no-sonar control session and either two successive ramp-up sessions (RampUp1, RampUp2) or a ramp-up session (RampUp1) and a full-power session (FullPower). Full-power sessions were conducted only twice; for other whales we used acoustic modelling that assumed transmission of the full-power sequence during their no-sonar control. Averaged overall whales, risk indicators in RampUp1 (n=11) differed significantly from those in FullPower (n=12) by -3.0 dB (SPLmax), -2.0 dB (SELcum) and +168 m (Rmin), but not significantly from those in RampUp2 (n=9). Only five whales in RampUp1, four whales in RampUp2 and none in FullPower or control sessions avoided the sound source. For RampUp1, we found statistically significant differences in risk indicators between whales that avoided the sonar and whales that did not: -4.7 dB (SPLmax), -3.4 dB (SELcum) and +291 m (Rmin). In contrast, for RampUp2, these differences were smaller and not significant. This study suggests that sonar ramp-up has a positive but limited mitigative effect for humpback whales overall, but that ramp-up can reduce the risk of harm more effectively in situations when animals are more responsive and likely to avoid the sonar, e.g. owing to novelty of the stimulus, when they are in the path of an approaching sonar ship. © 2017. Published by The Company of Biologists Ltd |.

In seismic surveys, reflected sounds from airguns are used under water to detect gas and oil below the sea floor. The airguns produce broadband high-amplitude impulsive sounds, which may cause temporary or permanent threshold shifts (TTS or PTS) in cetaceans. The magnitude of the threshold shifts and the hearing frequencies at which they occur depend on factors such as the received cumulative sound exposure level (SELcum), the number of exposures, and the frequency content of the sounds. To quantify TTS caused by airgun exposure and the subsequent hearing recovery, the hearing of a harbor porpoise was tested by means of a psychophysical technique. TTS was observed after exposure to 10 and 20 consecutive shots fired from two airguns simultaneously (SELcum: 188 and 191 dB re 1 μPa2s) with mean shot intervals of around 17 s. Although most of the airgun sounds' energy was below 1 kHz, statistically significant initial TTS1-4 (1-4 min after sound exposure stopped) of ∼4.4 dB occurred only at the hearing frequency 4 kHz, and not at lower hearing frequencies tested (0.5, 1, and 2 kHz). Recovery occurred within 12 min post-exposure. The study indicates that frequency-weighted SELcum is a good predictor for the low levels of TTS observed. © 2017 Acoustical Society of America.

Corrosion is one of the industries major issues regarding the integrity of assets. Currently inspections are conducted at regular intervals to ensure a sufficient integrity level of these assets. There are many situations where the actual defect location is not accessible, e.g., a pipe support or a partially buried pipe. Last year an approach was presented using a phase inversion of guided waves that propagated around the circumference of a pipe. This approach works well for larger corrosion spots, but shows significant under-sizing of small spots due to lack of sufficient phase rotation. In this paper the use of arrival time and amplitude loss of higher order circumferential passes is evaluated. Using higher order passes increases sensitivity for sizing smaller defects. Different defect profiles are assumed and the change in arrival time and amplitude loss are calculated using a wave equation based approach for different defect widths and depths. This produces a differential travel time and amplitude change map as function of defect depth and defect width. The actually measured travel time change and amplitude change produces two contours in these maps. Calculating the intersection point gives the defect dimensions. The contours for amplitude loss and travel time change are quite orthogonal, this yields a good discrimination between deep and shallow defects. The approach is evaluated using experimental data from different pipes contain artificial and real defects. © 2017 Author(s). QNDE Programs

Corrosion is one of the industries major issues regarding the integrity of assets. Currently inspections are conducted at regular intervals to ensure a sufficient integrity level of these assets. There are many situations where the actual defect location is not accessible, e.g., a pipe support or a partially buried pipe. Last year an approach was presented using a phase inversion of guided waves that propagated around the circumference of a pipe. This approach works well for larger corrosion spots, but shows significant under-sizing of small spots due to lack of sufficient phase rotation. In this paper the use of arrival time and amplitude loss of higher order circumferential passes is evaluated. Using higher order passes increases sensitivity for sizing smaller defects. Different defect profiles are assumed and the change in arrival time and amplitude loss are calculated using a wave equation based approach for different defect widths and depths. This produces a differential travel time and amplitude change map as function of defect depth and defect width. The actually measured travel time change and amplitude change produces two contours in these maps. Calculating the intersection point gives the defect dimensions. The contours for amplitude loss and travel time change are quite orthogonal, this yields a good discrimination between deep and shallow defects. The approach is evaluated using experimental data from different pipes contain artificial and real defects. © 2017 Author(s). QNDE Programs

In this paper we present the NECSAVE system which allows the control of heterogeneous unmanned vehicles under challenging environments by a single human operator by providing it with the desired highlevel objectives. The described software stack takes care of decomposing the high-level objectives into assignable tasks and (re)distributing the workload among team members according to their announced capabilities and eventual failures. NECSAVE is robust to system failures by supporting decentralized planning and adapting allocation in face of platform losses. The system was validated in multiple field trials where NECSAVE was used for the coordination of heterogeneous vehicles under challenged communication environments, namely the sea using radio (at surface) and acoustic communications (underwater).

The ocean is nearly transparent to low frequency sound permitting the observation of distant events such as earthquakes or explosions at fully basin scales. For very low frequency the ocean acts as a shallow-water waveguide and lateral variability in bathymetry can lead to out-of-plane effects. In this paper, data from the International Monitoring System of the Comprehensive Test Ban Treaty Organization (CTBTO) is used to present two cases where robustly localized seismic events in locations clearly within the two-dimensional (2-D) shadow of a continent or large island generate T-phase signals that are received on a hydro-acoustic station. A fully three- dimensional parabolic equation model is used to demonstrate that lateral variability of the bathymetry can lead to diffraction, explaining both observations. The implications of this are that the CTBTO network has greater coverage than predicted by 2-D models and that inclusion of diffraction in future processing can improve the automatic global association of hydroacoustic events. © 2017 Acoustical Society of America.

Exposure to underwater sound can cause permanent hearing loss and other physiological effects in marine animals. To reduce this risk, naval sonars are sometimes gradually increased in intensity at the start of transmission ('ramp-up'). Here, we conducted experiments in which tagged humpback whales were approached with a ship to test whether a sonar operation preceded by ramp-up reduced three risk indicators - maximum sound pressure level (SPLmax), cumulative sound exposure level (SELcum) and minimum source-whale range (Rmin) - compared with a sonar operation not preceded by ramp-up. Whales were subject to one no-sonar control session and either two successive ramp-up sessions (RampUp1, RampUp2) or a ramp-up session (RampUp1) and a full-power session (FullPower). Full-power sessions were conducted only twice; for other whales we used acoustic modelling that assumed transmission of the full-power sequence during their no-sonar control. Averaged overall whales, risk indicators in RampUp1 (n=11) differed significantly from those in FullPower (n=12) by -3.0 dB (SPLmax), -2.0 dB (SELcum) and +168 m (Rmin), but not significantly from those in RampUp2 (n=9). Only five whales in RampUp1, four whales in RampUp2 and none in FullPower or control sessions avoided the sound source. For RampUp1, we found statistically significant differences in risk indicators between whales that avoided the sonar and whales that did not: -4.7 dB (SPLmax), -3.4 dB (SELcum) and +291 m (Rmin). In contrast, for RampUp2, these differences were smaller and not significant. This study suggests that sonar ramp-up has a positive but limited mitigative effect for humpback whales overall, but that ramp-up can reduce the risk of harm more effectively in situations when animals are more responsive and likely to avoid the sonar, e.g. owing to novelty of the stimulus, when they are in the path of an approaching sonar ship. © 2017. Published by The Company of Biologists Ltd |.

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 identified. To maximize the bandwidth utilization of underwater communication links, a modulation that provides the possibility to have multiple QoS levels within a single transmission is introduced. This flexible modulation is labelled Multi-Stream Frequency-Repetition Spread Spectrum (MSFRSS) and provides configurable quality-of-service levels for distinct parts of the communicated message. Early channel replay simulations encourage future tests of MSFRSS in alternative configurations and environments

Acoustic underwater communication is an enabler for the use of autonomous underwater vehicles (AUVs). AUVs can operate in acoustically challenging environments, e.g., near offshore platforms and in harbours. To realize robust underwater communication in such environments, the propagation conditions need to be properly understood. In this paper, the performance of underwater acoustic communication in shallow water harbour environments is investigated. To perform our investigation, channel soundings (i.e., empirical channel impulse responses) captured in the Port of East-Vlissingen (The Netherlands) are employed. In particular, it is investigated how the increase of acoustic reverberation caused by reflections from physical structures in a harbour (e.g., quay walls, jetties, piers) affects the underwater acoustic communication performance. The empirical reverberation obtained from the channel soundings is compared with the modelled two-dimensional equivalent in order to make a distinction between bottom-surface paths and reflections from physical structures in the harbour. The collected channel soundings and their analysis are necessary for the development of novel modulation methods and provide useful input for an improved understanding of the acoustic propagation conditionsin harbour environments. The findings in this paper can be used by future tools for autonomous underwater operations.

Thecontributionofshippingnoisetothebackground noise in the seas can be estimated by shipping noise maps. Noise maps can be made by applying appropriate modeling tools for underwater sound propagation and ship source levels to information on the acoustic environment and on the ship traffic in the area of the map. The development of reliable source level models requires the availability of a variety of radiated noise data of ships. Therefore, full-scale radiated noise measurements were performed near ashippinglaneincoastalwatersoutofthePortofRotterdam.The results of the noise measurements are combined with information about the measured ships and their positions, derived from registered AIS data, and with propagation conditions to determine source levels. Criteria have been developed to select the data from which a reliable source level estimation can be obtained from individual ship passages at the busy shipping lanes. Source levels of different types of ships are compared.

Acoustic Mitigation Devices (AMDs) are used to deter marine mammals from construction sites, in order to prevent hearing injury by offshore pile driving noise. To estimate the distance at which two AMDs designed as ‘seal scarers’ (Ace Aquatec and Lofitech) are detected by harbor porpoises, the 50% hearing detection thresholds for playbacks of recordings of the AMD sounds were assessed. Both became audible at a received broadband sound pressure level (SPL) of 55 dB re 1 µPa. The effect of the AMDs on porpoise behavior was quantified at three SPLs determined during a pre-test: one which just did not cause a behavioral change, one which caused a small change in surfacing and swimming pattern, and one which caused the harbor porpoise to swim away from the transducers. The corresponding mean received SPLs in the pool were respectively: Ace Aquatec: 77, 117, and 139 dB re 1 µPa; and: Lofitech: 91, 121, and 151 dB re 1 µPa. As the mean received SPL increased, greater displacement occurred, and higher numbers of surfacings and increased swimming speed occurred in test periods than in associated baseline periods. By combining these results with the source level, the current local propagation conditions and the background noise, the deterring distance at sea for the AMDs can be calculated.

Reliable localization of marine mammals using towed arrays is often required for mitigation, population density estimates, and bioacoustics research. The accuracy of the range estimates using towed arrays is often not well quantified. Triangulation methods using multiple hydrophones allow for fast range estimates but are sensitive to the species type, location of the animal with respect to the array, sound propagation conditions, and array stability. A simple model is presented that is used to estimate the range accuracy of towed arrays for different vocalizations and is compared to measured range accuracies of sperm whale clicks recorded with a 15m baseline towed array. The ranging performance is particularly sensitive to hydrophone position errors which are found to dominate. Hydrophone position errors could be estimated using heading sensors placed in the array and are taken into account in the model. A good agreement is found between the empirical range errors and theoretically predicted ones. Extrapolation of the model to other species suggests that species emitting high frequency clicks and calls can be localized from distances out to a few kilometers with a baseline of 15 m, but baleen whales transmitting low frequency calls require longer baselines to obtain range estimates. VC 2013 Acoustical Society of America.

Well-calibrated scaling relations between the observable properties and the total masses of clusters of galaxies are important for understanding the physical processes that give rise to these relations. They are also a critical ingredient for studies that aim to constrain cosmological parameters using galaxy clusters. For this reason much effort has been spent during the last decade to better understand and interpret relations of the properties of the intra-cluster medium. Improved X-ray data have expanded the mass range down to galaxy groups, whereas SZ surveys have openened a new observational window on the intracluster medium. In addition,continued progress in the performance of cosmological simulations has allowed a better understanding of the physical processes and selection effects affecting the observed scaling relations. Here we review the recent literature on various scaling relations, focussing on the latest observational measurements and the progress in our understanding of the deviations from self similarity., 38 pages. Review paper. Accepted for publication in Space Science Reviews (eds: S. Ettori, M. Meneghetti). This is a product of the work done by an international team at the International Space Science Institute (ISSI) in Bern on "Astrophysics and Cosmology with Galaxy Clusters: the X-ray and Lensing View"

Proper spatial sampling is critical for high quality imaging. If the sampling criterion is not met, grating lobe artifacts appear in the image. In non-destructive testing applications efficiency is being increased by the steady enlargement of the field of view, resulting in more elements and thus a higher transducer complexity and cost. In the volume scanning methods used in medical applications, the challenge lies in connecting the 2500+ elements of a matrix array to

In this article we investigate the performance of underwater acoustic communications between an AUV and a ground control station in a realistic use case for harbor protection/monitoring in the North Sea. In particular we focus on the contribution of nearby shipping noise and how it influences the maximum communication range of an underwater modem in two relevant frequency bands for high and low data rate communications. Our results suggest that acoustic communication performance is highly dependent on in situ shipping conditions and future tools for autonomous operation planning in harbor environment must take into account this effect to ensure efficiency and robustness.

For decentralized fusion problems, ellipsoidal intersection has been proposed as an efficient fusion rule that provides less conservative results as compared to the well-know covariance intersection method. Ellipsoidal intersection relies on the computation of a common estimate that is shared by the estimates to be fused. In this paper, an algebraic reformulation of ellipsoidal intersection is discussed that circumvents the computation of the common estimate. It is shown that ellipsoidal intersection corresponds to an internal ellipsoidal approximation of the intersection of covariance ellipsoids. An interesting result is that ellipsoidal intersection can be computed with the aid of the Bar-Shalom/Campo fusion formulae. This is achieved by assuming a specific correlation structure between the estimates to be fused.

A new European Defence Agency (EDA) project is currently being set up, called SALSA, in which five European nations are working towards a common underwater communication stack for heavy-duty purposes, i.e., a rugged protocol stack that can serve as the future communication backbone for naval operations involving autonomous underwater vehicles (AUV) and bottom nodes. The emerging NATO standard JANUS is envisioned as first-contact protocol in the SALSA stack, enabling ad-hoc extensions of the underwater network such as in-mission upscaling of the number of AUVs in joint operations. In this context, the JANUS modulation has been tested at sea for several communication ranges and Doppler shifts, comparing its performance with the candidate physical-layer protocol of the SALSA stack.

As concern about anthropogenic noise and its impacts on marine fauna is increasing around the globe, data are being compared across populations, species, noise sources, geographic regions, and time. However, much of the raw and processed data are not comparable due to differences in measurement methodology, analysis and reporting, and a lack of metadata. Common protocols and more formal, international standards are needed to ensure the effectiveness of research, conservation, regulation and practice, and unambiguous communication of information and ideas. Developing standards takes time and effort, is largely driven by a few expert volunteers, and would benefit from stakeholders’ contribution and support.