Estimated Source Levels Research Articles

Source level of wind-generated ambient sound in the oceana).

Inference of source levels for ambient ocean sound from local wind at the sea surface requires an assumption about the nature of the sound source. Depending upon the assumptions made about the nature of the sound source, whether monopole or dipole distributions, the estimated source levels from different research groups are different by several decibels over the frequency band 10-350 Hz. This paper revisits the research issues of source level of local wind-generated sound and shows that the differences in estimated source levels can be understood through a simple analysis of the source assumptions.

Outdoor acoustic measurements of a rocket engine hot fire test

The primary focus of this paper is to present the results from outdoor acoustic measurements from a rocket engine hot fire test. The two objectives of the test were to quantify the overall sound pressure level at large distances from engine to quantify the impact of the events on the surrounding community, and to better understand the source distribution in the engine plume. Microphone arrays were positioned around the property to be able to capture the sound propagation, estimate source levels, and conduct phased array-based plume source localization.

Whale-watch vessel noise levels with applications to whale-watching guidelines and conservation

The number and size of whale-watching and swim-with-cetacean vessels are increasing worldwide, but the noise impact on targeted species depends on vessel source characteristics, which remain largely unquantified. Here, we report the acoustic characteristics from 13 whale-watching vessels from Australia and Canary Islands. Acoustic recorders were deployed to measure the frequency-weighted sound levels (for low [LF], mid [MF] and high frequency [HF] cetacean hearing types) of motor sailing, catamarans, and motor vessels operating at 4–8 kn representing the slow speed of whale-watch scenarios. The highest estimated source levels (SLs) were recorded from large catamarans with inboard engines (LF = 160 ± 3, MF = 148 ± 2, HF = 146 ± 2 dB re 1 µPa m). The lowest SLs were from smaller motor vessels and particularly by a hybrid vessel powered by electrical outboard engines (LF = 140 ± 3, MF = 136 ± 2, HF = 134 ± 2 dB re 1 µPa m). We demonstrate that at the same speed and distance, different vessels may produce very different received levels to the animals. To reduce disturbance to cetaceans we recommend tourism vessels meet a broadband (0.2–10 kHz) SL limit of <150 dB re 1 µPa (RMS) when within 500 m of cetaceans.

Underwater noise of commercial vessels in Nusakambangan Strait and the relationship with distance

The existence of shipping activities can produce noise with certain characteristics as a main source of noise pollution in the waters. This research aimed to study the sound characteristics (frequency and sound pressure levels) of various type of commercial vessels crossing the Nusakambangan Strait, its relationship to the distance, and their potential impact to the marine biota. Noise frequency and sound pressure level were determined by spectral and envelope analysis from sound recording by hydrophone, while the type of vessel that produces noise and the distance from receiver were analyzed based on video recording. Relationship between frequency and sound pressure level to the distance were analyzed using simple linear regression. Results showed that frequency of noise is varied more clearly compared to the sound pressure level (1,7 – 20 kHz and 93.8 -117.8 dB re 1 μPa respectively) for each type of vessel (ro-ro ferry, small fishing boat, small ferry, tug boat and pilot boat) based on the size of the ship, engines type and power, loading capacity and vessels speed. Sound characteristics changed based on distance, where the frequency of sound increases (0.04 – 34.28 Hz.m-1) and different things for sound pressure level (0.04 – 0.11 dB dB re 1 μPa m-1). Estimated source level also differ from one ship to another (105 – 128 dB dB re 1 μPa). The existence of ship noise has the potential impacts on the presence of marine biota in these waters.

수중방사소음 예측을 위한 빔형성 방법 기반 추진기 캐비테이션 음원준위 추정

In general, the prediction of underwater radiated noise requires source level information. This study proposes a method for the source level estimation of propeller cavitation based on the beamforming method. The proposed method obtains the source level information by determining the source strength corresponding to the estimated cavitation position. As the solution of the minimization problem can be determined analytically rather than numerically, it has the advantage of fast computational time. The proposed method is verified through a model-scale test conducted in a large cavitation tunnel of Korea Research Institute of Ships and Ocean Engineering. The estimated source level of the propeller cavitation matches well with a transfer-function-based method in the frequency band that satisfies the far-field. In addition, another method for reducing the computational time is considered through determining the source level from the cavitation position and sound pressure level.

Quantifying ship noise in the marine soundscape of the western Canadian Arctic

The Arctic soundscape is naturally quite complex, but many parts of the Arctic have also historically had very low levels of ship noise. However, ship traffic is increasing throughout the Arctic, which is likely leading to increased levels of underwater noise, causing changes in this soundscape. In this study, we thoroughly quantified ship noise in passive acoustic data collected at 10 sites in the western Canadian Arctic between 2014 and 2020, with data collected from between one and three years at each site. We paired the acoustic data with automatic identification system ship data to collect information on the individual ships creating noise. We quantified the presence of ship noise within all of the acoustic data, statistically examined the influence of different static and dynamic ship variables on sound levels, and estimated source levels of ships that traveled close to the acoustic recorder. These analyses represent the first detailed examination of ship noise in this region of the Arctic, and the results provide valuable information for future soundscape studies, as well as relevant information for the management of ship noise in the Arctic.

Transmission loss of Fish Spawning Vocalizations and the Detection Range of Passive Acoustic Sampling in Very Shallow Estuarine Environments

Acoustic signaling in fish is commonly associated with spawning and sound production has been used to identify spawning sites for multiple species. However, the transmission loss of those signals and subsequent ranges at which those sounds can be detected are often not accounted for, confounding the spatial resolution of those studies. We examined transmission loss of spotted seatrout (Cynoscion nebulosus) vocalizations in four habitat types (mud, seagrass, channel edges, and structures) within the very shallow (< 10 m) environment of an estuary. Recorded C. nebulosus vocalizations were projected through an underwater speaker while hydrophones measured the sound pressure levels along transects at doubling distances 2–512 m from the source. A linear-log regression was used to compare transmission loss across sites as a function of distance, and a mixed effects model was used to estimate the impact of distance, water depth, temperature, and salinity on the rate of transmission loss. Sounds were rapidly attenuated as the slopes of the regression lines ranged from − 14.9 to − 22.9 and were significantly different among sites. After distance from the source, water depth had the greatest effect on transmission loss in the mixed effects model, although sound is likely propagating through the sediment at all sites. Sound was most quickly attenuated in the channel edge habitat and least attenuated in the mud habitat. Considering the rate of transmission loss, the estimated source level of C. nebulosus sounds, and the background noise level during spawning, the detection range of passive acoustic sampling varied between 44 and 281 m from the source. These results indicate that the spatial precision of passive acoustic sampling of fish within the estuary is < 281 m, but that habitat type and water depth should also be considered when designing sampling protocols and estimating the location of vocalizing fish.

Estimation of the Noise Source Level of a Commercial Ship Using On-Board Pressure Sensors

The dominant underwater noise source of a ship is known to be propeller cavitation. Recently, attempts have been made to quantify the source strength using on-board pressure sensors near the propeller, as this has advantages over conventional noise measurement. In this study, a beamforming method was used to estimate the source strength of a cavitating propeller. The method was validated against a model-scale measurement in a cavitation tunnel, which showed good agreement between the measured and estimated source levels. The method was also applied to a full-scale measurement, in which the source level was measured using an external hydrophone array. The estimated source level using the hull pressure sensors showed good agreement with the measured one above 400 Hz, which shows potential for noise monitoring using on-board sensors. A parametric study was carried out to check the practicality of the method. From the results, it was shown that a sufficient recording time is required to obtain a consistent level at high frequencies. Changing the frequency resolution had little effect on the result, as long as enough data were provided for the one-third octave band conversion. The number of sensors affected the mid- to low-frequency data.

Bottom trawling noise: Are fishing vessels polluting to deeper acoustic habitats?

The impact of bottom trawling noise was quantified on two surrounding marine acoustic habitats using fixed mooring acoustic recorders. Noise during trawling activity is shown to be considerably louder than ambient noise and a nearby underway research vessel. Estimated source levels were above cetacean damage thresholds. Measurements at a submarine canyon indicated potential noise focussing, inferring a role for such features to enhance down slope noise propagation at continental margin sites. Modelled sound propagates more efficiently when sourced from trawling gear dragging along the seabed relative to the vessel as a surface source. Results are contextualised with respect to marine mammal harm, to other anthropogenic ocean noise sources, topography and seasons. Noise energy emitted by bottom trawling activity is a source of pollution that requires further consideration, in line with other pervasive trawling pressures on marine species and seabed habitats, especially in areas of heightened ecological susceptibility.

Source level measurements of killer whale (Orcinus orca) echolocation clicks

Biosonar is vital to odontocetes (toothed whales, dolphins, and porpoises) for navigation and finding food. Consequently, numerous details of their echolocation click parameters, such as source level and beam width, are known for many species; however, there is a data gap for killer whales (Orcinus orca). This information is essential for examining masking potential which could have an impact on their foraging abilities. The Southern Resident killer whales are an endangered population of orcas living along the Pacific coast of North America and underwater noise has been identified as a major threat towards their survival. This study used a 3D 24-element hydrophone array deployed in close proximity to wild killer whales to estimate source levels (SLs) and spectra of echolocation clicks. Future work will use these SLs to investigate masking potential from current and other noise scenarios.

Comparison of estimated 20-Hz pulse fin whale source levels from the tropical Pacific and Eastern North Atlantic Oceans to other recorded populations.

Passive acoustic monitoring, mitigation, animal density estimation, and comprehensive understanding of the impact of sound on marine animals all require accurate information on vocalization source level to be most effective. This study focused on examining the uncertainty related to passive sonar equation terms that ultimately contribute to the variability observed in estimated source levels of fin whale calls. Differences in hardware configuration, signal detection methods, sample size, location, and time were considered in interpreting the variability of estimated fin whale source levels. Data from Wake Island in the Pacific Ocean and off Portugal in the Atlantic Ocean provided the opportunity to generate large datasets of estimated source levels to better understand sources of uncertainty leading to the observed variability with and across years. Average seasonal source levels from the Wake Island dataset ranged from 175 to 188 dB re 1 μPa m, while the 2007-2008 seasonal average detected off Portugal was 189 dB re 1 μPa m. Owing to the large inherent variability within and across this and other studies that potentially masks true differences between populations, there is no evidence to conclude that the source level of 20-Hz fin whale calls are regionally or population specific.

Spatial mapping of the biophony of the fishes living in seagrass meadows

Passive acoustics is well suited to assess the diversity and/or activity of marine animals, particularly if cryptic or difficult to observe as in seagrass Posidonia oceanica meadows. The ability to locate the emitters allows not only to detect the presence of a specific sound or specie but also to estimate source levels, the communicative space with respect to ambient noise and anthropogenic impact, the density of vocalizing animals, their movements and potentially home ranges, etc. Here, we located fishes in seagrass meadows (Calvi, France). Two particular sounds dominated the acoustic scene of seagrass meadows: the: 300 Hz drums of Ophidion rochei and the ubiquitous 800Hz /kwa/ sound of unknown origin. The wavelengths of these fish sounds range from 5 m to 2 m. During six 48-hours period, we deployed a squared array of 4 hydrophones (20 x 50 x 50 m). Here, we describe the algorithm for automated fish sound detection and 3D localization of the sources and assess their performances on our real data. Over 1000 fish sounds were detected per night. These detections were used to create localization maps and study the spatial distribution of fish sound production, estimate source levels and the density of the vocalizing fishes within the meadow and their limits.

Development of beluga calf calls (Delphinapterus leucas) in the first six months of life

As part of an ongoing effort to understand beluga mother-calf communication and impacts of anthropogenic noise on neonate calls, we investigated a male beluga calf’s vocal development at Oceanogràfic, using a calibrated digital hydrophone with a sampling rate of 256 kHz. His initial vocalizations were broadband pulse-trains with upper frequency limits reaching ≥128 kHz on his first day of life, higher than reported by earlier studies limited by lower sampling rates. Over the calf’s first six months, pulsed trains were the predominant call type, increasing significantly in peak and first quartile frequencies and pulse repetition rate during this period. First and third quartile frequencies also increased significantly over the calf’s first month, indicating an early and continuous shift in pulse train energy distribution towards higher frequencies. While mixed and tonal calls appeared sporadically in the calf’s first month of life, they were not common until his third month, when they comprised 13% of his vocalizations. Additionally, estimated source levels of the calf’s calls increased throughout his first month, but were lower than those for adult belugas. This, coupled with the progressive shift in energy distribution, has important implications regarding a neonate’s ability to compensate for noise.

Automated passive acoustic detection, classification, localization, and tracking methods applied to recorded data from the Pacific Missile Range Facility, Kauai, Hawaii

Automated methods will be reviewed for performing passive acoustic detection, classification, localization, and tracking of some marine mammal species and man-made sources. The methods have been applied to recorded hydrophone data from a large aperture seafloor array at the Pacific Missile Range Facility (PMRF) at Kauai, Hawaii, with some of the methods currently implemented in a real-time system at PMRF. The process consists of custom software both in C + + and Matlab in a 3 or 4-step process. Automated detections of various sounds in specific frequency bands are first performed. In some cases, a classification stage is also performed. The third stage involves model-based localization of the detections or classifications. The fourth stage converts the localizations into individual source tracks. Source tracks are currently generated for fin, sei, Bryde’s, humpback, and sperm whales and mid-frequency active sonar (MFAS) transmissions. Performing this process on marine mammals allows information regarding the movement patterns of the whales while calling, as well as information on the species’ calls (e.g., call rate, frequencies, durations, estimated source levels). By performing similar processes on man-made sources, it is possible to determine some marine mammal responses from proximity of Navy vessels and mid-frequency active sonar sources.

Seismic and hydroacoustic analysis of four large underwater explosions off the east coast of Florida

During the summer of 2016, the US Navy detonated four large underwater explosions off the east coast of Florida as part of shock wave testing for the Littoral Combat Ships USS Jackson and USS Milwaukee. The water depth at the explosion site is 900 m. Videos of the events provide further insight into the sources. Originally listed as magnitude 3.7 earthquakes in USGS bulletins, the source types were changed to “Experimental Explosion” as the Navy began releasing information to local news stations. These explosions were recorded on US seismic stations to distances of ~2000 km and on the hydroacoustic array at Ascension Island at a distance of ~8100 km. Seismic signals are complex but cepstral analysis reveals a clear bubble pulse period of 1.15 sec, corresponding to source depths of 50 meters. At Ascension the signals arrive at an RMS level of 136 dB at an SNR of 30 dB. We modeled the propagation loss from the source to Ascension using broadband PE and find the propagation loss to be 126 dB. Backing out this loss, we estimate source levels for the two explosions at 262 dB corresponding to explosion yields of 11,000 lbs.

Source levels of harbor seal underwater reproductive advertisement displays

Harbor seals (Phoca vitulina), along with the majority of other phocid species, mate underwater. During the breeding season, male harbor seals set up underwater territories and use acoustic cues, known as roars, to defend these areas against intruder males and possibly to attract females. Vocalizations are low in frequency, predominately around 60-100 Hz, with some broadband components reaching up to 5 kHz, and range from 4-10 seconds in duration. Previously, source levels of vocalizations have only been estimated. Here we present a method for measuring vocalizations to estimate source levels of harbor seal roars. We used a three-element hydrophone array in Glacier Bay National Park to record harbor seal vocalizations during the breeding season (June—July 2015). Using the array, we localized individual vocalizing animals and calculated source levels of calls in the 40-500 Hz range. Knowledge of source levels for vocalizations of harbor seals is important for understanding how anthropogenic forces, such as noise from vessels, may impact the acoustic behavior and communication range of these animals.

Delphinid echolocation click detection probability on near-seafloor sensors.

The probability of detecting echolocating delphinids on a near-seafloor sensor was estimated using two Monte Carlo simulation methods. One method estimated the probability of detecting a single click (cue counting); the other estimated the probability of detecting a group of delphinids (group counting). Echolocation click beam pattern and source level assumptions strongly influenced detectability predictions by the cue counting model. Group detectability was also influenced by assumptions about group behaviors. Model results were compared to in situ recordings of encounters with Risso's dolphin (Grampus griseus) and presumed pantropical spotted dolphin (Stenella attenuata) from a near-seafloor four-channel tracking sensor deployed in the Gulf of Mexico (25.537°N 84.632°W, depth 1220 m). Horizontal detection range, received level and estimated source level distributions from localized encounters were compared with the model predictions. Agreement between in situ results and model predictions suggests that simulations can be used to estimate detection probabilities when direct distance estimation is not available.

Sperm whale predator-prey interactions involve chasing and buzzing, but no acoustic stunning.

The sperm whale carries a hypertrophied nose that generates powerful clicks for long-range echolocation. However, it remains a conundrum how this bizarrely shaped apex predator catches its prey. Several hypotheses have been advanced to propose both active and passive means to acquire prey, including acoustic debilitation of prey with very powerful clicks. Here we test these hypotheses by using sound and movement recording tags in a fine-scale study of buzz sequences to relate the acoustic behaviour of sperm whales with changes in acceleration in their head region during prey capture attempts. We show that in the terminal buzz phase, sperm whales reduce inter-click intervals and estimated source levels by 1–2 orders of magnitude. As a result, received levels at the prey are more than an order of magnitude below levels required for debilitation, precluding acoustic stunning to facilitate prey capture. Rather, buzzing involves high-frequency, low amplitude clicks well suited to provide high-resolution biosonar updates during the last stages of capture. The high temporal resolution helps to guide motor patterns during occasionally prolonged chases in which prey are eventually subdued with the aid of fast jaw movements and/or buccal suction as indicated by acceleration transients (jerks) near the end of buzzes.

Offshore Dredger Sounds: Source Levels, Sound Maps, and Risk Assessment.

The underwater sound produced during construction of the Port of Rotterdam harbor extension (Maasvlakte 2) was measured, with emphasis on the contribution of the trailing suction hopper dredgers during their various activities: dredging, transport, and discharge of sediment. Measured source levels of the dredgers, estimated source levels of other shipping, and time-dependent position data from a vessel-tracking system were used as input for a propagation model to generate dynamic sound maps. Various scenarios were studied to assess the risk of possible effects of the sound from dredging activities on marine fauna, specifically on porpoises, seals, and fish.

Underwater noise emissions from a drillship in the Arctic

Wideband sound recordings were made of underwater noise emitted by an active drillship, Stena Forth, working in 484m of water in Baffin Bay, western Greenland. The recordings were obtained at thirty and one-hundred meters depth. Noise was recorded during both drilling and maintenance work at ranges from 500m to 38km. The emitted noise levels were highest during maintenance work with estimated source levels up to 190dB re 1μPa (rms), while the source level during drilling was 184dB re 1μPa (rms). There were spectral peaks discernible from the background noise to ranges of at least 38km from the drillship with the main energy below 3kHz. M-weighted sound pressure levels were virtually identical to broadband levels for low-frequency cetaceans and about 5dB lower for high-frequency cetaceans. Signals from the dynamic positioning system were clearly detectable at ranges up to two km from the drillship.