Underwater Sound Measurements Research Articles

Validation of estimated underwater radiated noise propagation from a ship using the parabolic equation method by underwater sound measurements in actual sea

In 2022, the International Maritime Organization started a review of the nonmandatory guidelines for the reduction of underwater radiated noise (URN) from ships and a discussion about the next step. In the case of considering the extent of underwater radiated noise from a ship, the propagation of the URN and the background noise in the sea area should be considered in addition to the source level of the URN. In this study, the time series of the received levels of underwater sound measured off Izu-Oshima Island, Japan, are shown in the 1/3 octave band level. The time series of the received levels were compared with the propagation loss estimated by the parabolic equation method to validate the accuracy of the estimation of the propagation of underwater sound in the measurement area.

Intra-Articular Ultrasonography Probe for Minimally Invasive Upper Extremity Arthroscopic Surgery: A Phantom Study.

Upper extremity arthroscopic surgery is a highly technique-dependent procedure that requires the surgeon to assess difficult cartilage conditions and manage the risk of iatrogenic damage to nerves and vessels adjacent to the joint capsule in a confined joint space, and a device that can safely assist in this procedure has been in demand. In this study, we developed a small intra-articular ultrasound (AUS) probe for upper extremity joint surgery, evaluated its safety using underwater sound field measurement, and tested its visualization with a phantom in which nerves and blood vessels were embedded. Sound field measurement experiments confirmed the biological safety of the AUS probe's output, while confirming that sufficient output power level performance was obtained as an ultrasound measurement probe. In addition, images of blood vessels and nerves were reconstructed discriminatively using A-mode imaging of the agar phantom. This study provides proof-of-concept of the AUS probe in upper extremity surgery. Further studies are needed to obtain approval for use in future medical devices.

Statistical analysis of measured underwater radiated noise from merchant ships using ship operational and design parameters.

Ships unintentionally radiate underwater noise mainly due to propeller cavitation under usual operations. In 2022, the International Maritime Organization started a review of the nonmandatory guidelines for the reduction of underwater radiated noise (URN) from ships. The characteristics of URN from ships have been studied for a long time, and quantitative variations in URN levels with ship size and speed have been reported. From the viewpoint of ship design, it is more reasonable that the effect of ship speed and draft is considered as the ratio to design speed and maximum draft, respectively. Therefore, in this study, underwater sound measurements were conducted in deep water (>300 m in depth) under a sea lane, and regression analysis was applied to the source levels of the URN from many merchant ships using ship length, ship speed ratio to design speed, and draft ratio to maximum draft. In this analysis, the source level is simplified based on the characteristics of URN due to propeller cavitation. This allows one coefficient to represent the approximate shape of the spectrum of URN level. Further, variations in the URN level for each ship type are discussed based on the results and comparisons with previous studies.

The underwater sound levels of Lithuanian marine harbour

Aquatic animals rely on sound to communicate, navigate, prey, or avoid predation in turbid waters. The acoustic environment of their habitats plays an important role in their life, i.e. the fishes understand the environment using sound. Documented studies provide data indicating that marine habitats can be altered by anthropogenic noise, due to which marine life can be affected. The nearshore and the areas of harbours are usually predominated by the high sound pressure levels of anthropogenic origin resulting from frequent passages of pleasure vessels and other kind of ships nearby. These high levels no doubt can cause the risk of negative effects on marine life inhabited or migrating through nearshore and harbour areas. With the aim to assess the underwater sound levels at Klaipėda harbour area, underwater acoustic measurements were implemented. The obtained results indicate that the Klaipeda harbour is affected by the anthropogenic underwater noise and long-term noise monitoring may be useful to assess the trends of prevailing underwater noise in this area. In this paper, the results of the continuous underwater sound level measurements along with the analysis of the influence of anthropogenic sources and environmental factors on prevailing soundscape are presented; the risks of negative effects of elevated underwater noise levels on fish species and possible underwater noise measures are shortly discussed.

Spiral Sound Wave Transducer Based on the Longitudinal Vibration.

A spiral sound wave transducer comprised of longitudinal vibrating elements has been proposed. This transducer was made from eight uniform radial distributed longitudinal vibrating elements, which could effectively generate low frequency underwater acoustic spiral waves. We discuss the production theory of spiral sound waves, which could be synthesized by two orthogonal acoustic dipoles with a phase difference of 90 degrees. The excitation voltage distribution of the transducer for emitting a spiral sound wave and the measurement method for the transducer is given. Three-dimensional finite element modeling (FEM)of the transducer was established for simulating the vibration modes and the acoustic characteristics of the transducers. Further, we fabricated a spiral sound wave transducer based on our design and simulations. It was found that the resonance frequency of the transducer was 10.8 kHz and that the transmitting voltage resonance was 140.5 dB. The underwater sound field measurements demonstrate that our designed transducer based on the longitudinal elements could successfully generate spiral sound waves.

Monitoring of moving surface ship using a four-element planar hydrophone array installed on the seabed

This talk presents the analysis result of underwater sound measurement data which were recently gathered in the shallow water near South Korea. For the underwater sound measurement, a four-element planar hydrophone array developed by KRISO was installed on the seabed and recorded a month-long acoustic data. The result shows that the measured sound level is usually higher in the morning time and this is ascribed to the surface boats which are presumably in fishing activity. We deal with the identification of the sound sources via various modulation analysis methods which can discriminate the sound induced by rotating propellers and also discuss the direction finding by beamforming of the planar hydrophone array data. [This work was financially supported by the research project PNS3120 funded by KIGAM.]

Measurement and characterisation of radiated underwater sound from a 3.6 MW monopile wind turbine

This paper describes underwater sound pressure measurements obtained in close proximity (∼50 m) to two individual wind turbines, over a 21-day period, capturing the full range of turbine operating conditions. The sound radiated into the water was characterised by a number of tonal components, which are thought to primarily originate from the gearbox for the bandwidth measured. The main signal associated with the turbine operation had a mean-square sound pressure spectral density level which peaked at 126 dB re 1 μPa2 Hz-1 at 162 Hz. Other tonal components were also present, notably at frequencies between about 20 and 330 Hz, albeit at lower amplitudes. The measured sound characteristics, both in terms of frequency and amplitude, were shown to vary with wind speed. The sound pressure level increased with wind speed up to an average value of 128 dB re 1 μPa at a wind speed of about 10 ms-1, and then showed a general decrease. Overall, differences in the mean-square sound pressure spectral density level of over 20 dB were observed across the operational envelope of the turbine.

Long-term underwater sound measurements in the shipping noise indicator bands 63 Hz and 125 Hz from the port of Falmouth Bay, UK

Chronic low-frequency anthropogenic sound, such as shipping noise, may be negatively affecting marine life. The EU's Marine Strategy Framework Directive (MSFD) includes a specific indicator focused on this noise. This indicator is the yearly average sound level in third-octave bands with centre frequencies at 63Hz and 125Hz. These levels are described for Falmouth Bay, UK, an active port at the entrance to the English Channel. Underwater sound was recorded for 30min h−1 over the period June 2012 to November 2013 for a total of 435days. Mean third-octave levels were louder in the 125-Hz band (annual mean level of 96.0dB re 1μPa) than in the 63-Hz band (92.6dB re 1 μPa). These levels and variations are assessed as a function of seasons, shipping activity and wave height, providing comparison points for future monitoring activities, including the MSFD and emerging international regulation.

An Autonomous Underwater Recorder Based on a Single Board Computer.

As industrial activities continue to grow on the Brazilian coast, underwater sound measurements are becoming of great scientific importance as they are essential to evaluate the impact of these activities on local ecosystems. In this context, the use of commercial underwater recorders is not always the most feasible alternative, due to their high cost and lack of flexibility. Design and construction of more affordable alternatives from scratch can become complex because it requires profound knowledge in areas such as electronics and low-level programming. With the aim of providing a solution; a well succeeded model of a highly flexible, low-cost alternative to commercial recorders was built based on a Raspberry Pi single board computer. A properly working prototype was assembled and it demonstrated adequate performance levels in all tested situations. The prototype was equipped with a power management module which was thoroughly evaluated. It is estimated that it will allow for great battery savings on long-term scheduled recordings. The underwater recording device was successfully deployed at selected locations along the Brazilian coast, where it adequately recorded animal and manmade acoustic events, among others. Although power consumption may not be as efficient as that of commercial and/or micro-processed solutions, the advantage offered by the proposed device is its high customizability, lower development time and inherently, its cost.

Underwater Sound Measurements of a High-Speed Jet-Propelled Marine Craft: Implications for Large Whales

Radiated noise from a high-speed jet-propelled watercraft (the M/V Alakai, 1,646 tons, length 117 m) was measured at hydrophone depths of 3, 6, and 10 m while the ship passed by at speeds of 6.17333 m/sec (12 knots), 12.3467 m/sec (24 knots), and 19.0344 m/sec (37 knots). Noise spectra were similar for all speeds and hydrophone depths. Spectra peaked below 100 Hz and dropped off continuously at higher frequencies. Calculated source level noise was 10 to 20 dB lower than noise from propeller-driven ships and much lower than for ships of similar speed. Although exposure to noise radiating from the M/V Alakai over short time periods is unlikely to cause hearing damage to whales, the combination of low radiated noise levels and high transit speeds leads to a shorter closing time (defined as time between when source level of the ship at a stationary receiver is greater than ambient noise and time that a ship traveling directly toward the receiver arrives at its location) between ship and whale. Compared with other types of ships traveling at similar speeds, closing time for the Alakai ranges from 20 sec shorter (at 6.17333 m/sec [12 knots]) to 22 min shorter (at 19.0344 m/sec [37 knots]). Shortest closing time for the Alakai is 89.1 sec at a speed of 6.17333 m/sec (12 knots). Shortened closing time might reduce successful detection and avoidance of high-speed jet-propelled ships by whales, and increased speed shortens the time during which whales have the opportunity to respond to this detection.

Monitoring Greek Seas Using Passive Underwater Acoustics

AbstractThe Hellenic Center for Marine Research POSEIDON ocean monitoring and forecasting system has included passive underwater acoustic measurements as part of its real-time operations. Specifically, low-duty-cycle long-term passive acoustic listeners (PALs) are deployed on two operational buoys, one off Pylos in the Ionian Sea and the second off Athos in the northern Aegean Sea. The first step toward the quantitative use of passive ambient sound is the classification of the geophysical sources—for example, wind speed and rain rate—from the noise of shipping, from other anthropogenic activities, and from the natural sounds of marine animals. After classification, quantitative measurements of wind speed and precipitation are applied to the ambient sound data. Comparisons of acoustic quantitative measurements of wind speed with in situ buoy anemometer measurements were shown to be within 0.5 m s−1. The rainfall detection and quantification was also confirmed with collocated measurements of precipitation from a nearby coastal rain gauge and operational weather radar rainfall observations. The complicated condition of high sea states, including the influence of ambient bubble clouds, rain, and sea spray under high winds, was sorted acoustically, and shows promise for identifying and quantifying such conditions from underwater sound measurements. Long-term data were used in this study to derive sound budgets showing the percent occurrence of dominant sound sources (ships, marine mammals, wind, and rain), their relative intensity as a function of frequency, and statistical summaries of the retrieved rainfall amounts and wind speeds at the two buoy locations in the Aegean and Ionian Seas.

A practical weighting function for harbor porpoise underwater sound level measurements

Harbor porpoise (Phocoena phocoena) are subject to underwater noise disturbance from anthropogenic sources, especially shipping. The underwater audiograms of harbor porpoise were used to create a frequency weighting function, dBht(Phocoena phocoena), to permit estimation of the broadband perceived amplitudes of ambient and shipping noise. An equation was fit to the 0.02-20 kHz range of unmasked detection thresholds and normalizing to 0 dB at 20 kHz; dB = 46.4-35.6 log(kHz). The weighting function de-emphasizes the low frequency components of noise. Harbor porpoise hearing is less sensitive to low frequency shipping noise and, except at high amplitudes, estimating potential noise impacts using linear measurements will be misleading.

Sound Silencing Problem of Underwater Vehicles

This paper describes some common problems associated with negative influence of UUV self noise on detection aspect in water environment. Some tasks of military applications require silent behavior of UUVs: Intelligence, Surveillance, and Reconnaissance (ISR), Rapid Environmental Assessment (REA), Mine Countermeasure (MCM) etc. Moreover, this paper review methods of underwater sound measurement and on the end as a summary presents results of an experiment from the water tank trials where were investigated three UUVs: one ROV and two biomimetic autonomous underwater vehicle.

Acoustic monitoring of pile driving activities at the proposed NaiKun wind farm site.

Underwater sound level measurements were obtained during marine pile driving activities at the proposed NaiKun wind farm site in Hecate Strait, British Columbia, Canada. Three hollow steel piles 0.9 m in diameter were driven into the seafloor to secure in place a truss to support a meteorological instrumentation mast. The activities involved both vibro‐hammering and impact hammering. Measurements were collected at 10 m range to fulfill regulatory requirements for real‐time monitoring of the near‐source sound pressure levels and also at a selection of longer ranges to allow a characterization of the propagation conditions of the environment. A bubble curtain was utilized to mitigate the underwater noise generated by impact hammering after trial measurements over a few hammer strikes showed that unmitigated levels exceeded a regulatory threshold. Results from this study were used to derive source level estimates for a subsequent sound propagation modeling study conducted as part of the environmental assessment process. Results from the real‐time monitoring at 10 m from the source (with and without the use of the bubble curtain) and from measurements obtained between 100 m and 3 km range will be presented.

Blind deconvolution of remote‐source signals from ocean acoustic array recordings.

Reconstructing the signal originally broadcast from a remote source in an unknown multipath environment is a task commonly known as blind deconvolution. At frequencies of several kilohertz and above, multipath shallow‐ocean sound propagation may be adequately described by ray acoustics. This presentation describes results from the application of ray‐based artificial time reversal (ATR) to underwater sound propagation measurements. The receiving array was vertical and it recorded signals with center frequencies and bandwidths of a few kHz at source‐receiver ranges up to 3 km in a water depth of approximately 60 m. Ray‐based ATR uses a simple‐beam‐former‐determined ray‐arrival direction to construct a frequency‐dependent phase correction at the receiving array that allows the Green’s function of the sound channel and the original source waveform to be separately estimated. Here, the correlation coefficient between the original signal and the ATR‐reconstructed signal is presented as a function of range and signal‐to‐noise ratio. In addition, the effect of reducing the number elements of the receiving array and the use of a coherent combination of reconstructed results for various ray arrival directions on cross correlation coefficient will be discussed. [Work supported by ONR.]

Underwater sound measurements of the Hawaii super ferry and the potential impact to humpback whales in the main Hawaiian Islands.

Underwater measurements of the Hawaii Super Ferry were made with a vertical array of four hydrophones. The depths of the hydrophones were 3, 6.5, 10, and 20 m. The Alakai is a 107 m catamaran passenger and automobile ferry that has a waterjet propulsion system with no exposed propellers. The Alakai made three close proximity passes at speeds of 37, 24, and 12 kn on tracks that allowed for acoustic measurements of sounds radiating from the bow, broadside, and stern aspects. The track of the Alakai was recorded on global positioning system. The measurements were conducted while the ferry proceeded on normal scheduled trips, allowing for three measurements a day. All the sound pressure levels were referenced to 91 m (100 yards), the minimum legal approach distance of boats to humpback whales. Sound intensity increased with speed and was the highest at 37 kn in the broadside aspect (160 dB) and was 14 dB lower for both the bow and stern aspects. The sounds had a broadband noise quality with spectra that had a low frequency peak below 100 Hz and decreased continuously with frequency. The effects of the sounds will be discussed from a humpback whale perspective.

Transmission of low frequency sounds from ships into water environment

The main goal is presentation the broad experimental research associated with the transmission of acoustic energy generated by moving objects into the water. I present the methodology of evoluation of the transmission of low frequency vibration from the mechanisms of ship into the water environment. For that purpose the research of vibration distribution over ship's hull were conducted along with the hydroacoustic field. The underwater sound measurements were performed both for sailing condition and during anchorage. The hull is source of complex surface shape inducing waves of different frequencies depending on the working parameters of ship's machinery. As a result of mechanical incitement of the hull's surface a complex distribution of vibration is created depending on vibration spectra of the primary sources as for the main propulsion units, generators or other mechanisms. This research allowed to determine the transmission coefficient for the mechanical vibration energy going through the ship's hull and the evaluation of influence on the hydroacoustic field of a ship. The values signaling the changes of the technical condition of machinery and propulsion system.

The ASA standards program and underwater sound, are they incompatible?

In the ASA National Standards Catalog, there are over 70 standards that concern the measurement and evaluation of sound in air. There are only a few standards, such as ANSI S1.11-1986 (filters) or ANSI S1.22-1992 (underwater transducer calibration) that concern underwater sound. This latter standard is the only standard of the 111 current standards that specifically relates to underwater acoustics. Standards such as ANSI S1.26-1995 (absorption of sound by the atmosphere) or ANSI S12.9-1996 (measurement of occupational noise exposure) just do not have a counterpart for water. Is this because there is no need? Is there no value in standardizing some common practices for underwater sound measurement and evaluation? Is it indeed true that underwater sound needs few standards? Comments from the audience are expected.

Underwater rain noise : sources, spectra and interpretations

An overview over the most important results obtained over the past of noise produced in water by impacts of single droplets, artificial rain and real rain is presented. Two distinct sources form the major contributors to rainfall produced noise in the sea. The raindrop impact and the pulsations of entrained air bubbles. The impact sound is produced by raindrops of all sizes, while the bubble pulsations are connected with regular entrainment of small gas bubbles, leading to the characteristic peak spectral level between 14 and 16 kHz, and by irregular entrainment of larger gas bubbles produced by impact of large raindrops. The noise spectra are discussed and interpretations of their relations to the raindrop size and impact mechanisms are given. Relations between noise spectra and rainfall rates are discussed and some still unsolved problems are pointed out, particularly related to estimation of light and moderate rainfalls using underwater sound measurements.

System loss due to frequency limiting of bottom bounces

Abstract : Processing systems which incorporate rather narrow frequency acoustic windows are often used for underwater sound measurements. When sound is being received which has bounced off the rough bottom of the ocean, some of the energy being received has returned from points on the bottom which are far from the point of specular reflection between source and receiver. Some Doppler shift is associated with these off-specular reflections when compared with the specular point. In this way, frequency spreading occurs. Thus, some of the acoustic energy returning from the bottom is lost as it is outside the frequency window used by the receiver. It is the goal of this thesis to produce an approximation of this loss, to test the approximation and to understand how the loss level is affected by environmental parameters. A theoretical approximation for the bottom loss integral is derived for the case of a stationary measurement point and an approaching source. Acoustic reflections from the hard, rougher basement are included as well as the energy returned by the overlaying sediment. The final result is compared with the calculations of a computer-based complete model, and conclusions are made concerning the validity of the model.