bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound generated by an elastic wing actuated at its leading edge.
Authors: Manela Avshalom
Published: July 2011

The sound generated by a thin elastic plate, subject to uniform low-Mach flow and to leading-edge pitching and heaving motions, is studied. The linearized plate motion is analyzed under conditions where the unforced plate (in the absence of leading-edge actuation) is stationary. When the frequency of applied forcing coincides with an eigenfrequency ωres of the unforced plate, a resonance motion is excited and the plate oscillates at the corresponding eigenmode. The sources of sound in the problem include the plate velocity and fluid vorticity. Acoustic radiation of dipole type is calculated and discussed in the limit of an acoustically compact plate. It is found that plate elasticity has two opposite effects on sound radiation: close to ωres, elasticity results in the generation of high sound pressure levels; however, far from ωres, elasticity tends to reduce the amplitude of plate deflection (compared to that of a rigid plate), leading to reduced sound levels. It is also shown that the release of trailing-edge vortices is the main source of sound, dominating the radiation from the direct plate motion. The present theory is suggested as a simple tool for analyzing insect-flight sound and predicting the acoustic signature of flapping micro-air-vehicles.
Coupled structural-acoustic computations for interior problems using a modal solution for the structural vibrations and a direct solution for the acoustic pressure field.
Authors: Fahnline John B.
Published: July 2011

Structural-acoustic computations involving enclosed volumes of fluid using finite elements are often performed by coupling in vacuo structural modes with acoustic modes derived assuming rigid-wall boundary conditions, sometimes referred to as Dowell’s method. This approach works well for problems with “light” fluid coupling, but is very slow to converge for problems with “heavy” fluid coupling. Several authors have suggested methods to derive terms to add to the acoustic basis set to account for the residual contributions of truncated modes. Another possibility, which will be the focus of this paper, is to directly compute the acoustic field in terms of nodal pressure variables rather than as a modal summation. Despite the relative simplicity of this approach, it does not appear to have explored previously in the literature. As will be shown, the coupled structural-acoustic equation system closely resembles that for coupled finite element/boundary element problems because both are written in terms of the structural variables only. The main goal of the presentation will be to demonstrate that using a direct solution for the acoustic field alleviates the slow convergence difficulties encountered with Dowell’s method for coupled structural-acoustic analyzes.
Analysis of results of numerical calculations of sound scattering by inhomogeneous elastic shells aiming to create a physical model of the scatterer.
Authors: Salin Mikhail B.
Published: July 2011

Determining vibration and acoustic characteristics of elastic bodies in water (especially elastic shells) is a challenging problem that becomes more complicated if non-homogeneities of various types are present or a finite length object is considered (∼1–10 wavelengths). Scattering by such bodies is considered here. This paper describes methods of analysis of results of numerical calculations that allow one to find the scattering mechanisms that make the greatest contribution to the scattered directivity pattern. The method allows one to distinguish the following factors: scattering as if it were a rigid body and excitation of an eigenmode, whose form can also be roughly estimated. The scattering object is replaced virtually by a discrete receiver-transmitter array whose transmitted signal is defined as the product of the received signal and the scattering matrix. Elements of the scattering matrix are found in such way that calculated scattered field values in the far field are close to the real ones. The results of this research can help in such areas as designing structures with required scattering characteristics, solving inverse problems and in classification and remote sensing. [The author gratefully acknowledges the generous support of the U.S. Office of Naval Research, ONRG.]
Low-wavenumber turbulent boundary layer wall-pressure measurements from vibration data on smooth and rough cylinders in pipe flow.
Authors: Evans Neal D. , Capone Dean E. , Bonness William K.
Published: July 2011

The vibration response of a thin cylindrical shell excited by a fully-developed turbulent boundary layer is measured and used to extract the fluctuating pressure levels generated by the boundary layer. Parameters used to extract the turbulent boundary layer pressure levels are determined via experimental modal analysis of the water-filled pipe and measured vibration levels from flow through the pipe at 6 m/s. Hydrostatic head from a large reservoir provides the low-noise source of steady flow for measuring the low-wavenumber fluctuating pressure levels. Measurements are reported for smooth, transitionally rough, and fully rough conditions and are compared to the turbulent boundary layer pressure models of Chase, Smol’yakov, and Howe.
Determination of pipe interior pressures using external accelerometers.
Authors: Salton Alexandria R. , Capone Dean E. , Bonness William K.
Published: July 2011

A non-invasive method utilizing a ring of accelerometers to measure pipe interior pressures is presented. The internal acoustic pressure of the fluid inside a cylindrical pipe is directly related to the vibrations at the surface due to the coupling of the fluid and structure. The n=0 breathing mode provides the basis for this relation and is extracted from operational data using a circumferential modal decomposition routine. The measurement of pipe interior pressures can be useful in determining the integrity of a piping system by detecting high pressures, which may lead to the fatigue or failure of the system. Within the field, a non-invasive method for measuring these pressures is more practical in comparison to the intrusive but more direct method of using hydrophones. Measurements using the ring of accelerometers are compared to hydrophone measurements to determine accuracy.
Sonic speed estimates for muddy sediments with plausible microbubble distributions.
Authors: Carey William M. , Pierce Allan D.
Published: July 2011

Measurements of the sound speed characteristic of the high porosity Dodge Pond mud were found to have a sonic speed less than that observed by Wood and Weston [Acustica 14, (1964)], a compressional speed 3% less than that of water. Other experiments performed on muddy sediments at frequencies greater than 1 kHz are consistent with the Dodge Pond observations when microbubbles are present. The presence of bubbles is known to be an important factor in decreasing the sound speed. A theoretical treatment of “muddy sediments,” the card house theory [Pierce and Carey, POMA 5, 7001, (2009)], estimated the slow sound speed and frequency dispersion proportional to mud porosity, Cmud ≈ (0.91–0.97)Cw. The presence of microbubbles can lower the sound speed consistent with the Mallock–Wood equation when the bubble size distribution and mean bubble separation are less than the wavelength of the propagating wave. Since measurement of the bubble size distribution within the mud is difficult; theoretical limits on the size distribution in the complex card house structure can be useful in interpreting measurements on muddy sediments and provide a basis for acoustic distribution measurement. [Work supported by the ONR OA and the NSWC PCD.]
Estimation of the shear wave speed in mud based on a card-house theory with elastic platelets.
Authors: Fayton Joseph O. , Pierce Allan D. , Carey William M. , Siegmann William L.
Published: July 2011

Principal constituents of mud ocean sediments are small platelets of minerals such as smectite and kaolinite. Isomorphous substitution produces negative charges on platelets, and salt water ions rearrange to cause an effective quadrupole moment per unit area of platelet. A card-house structure results, where an edge of one platelet is bonded to the face of another and where each platelet is in a state of electrostatic equilibrium. Platelets are idealized as elastic plates, with a bending modulus proportional to Eh3. The elastic modulus E can be estimated from chemical physics principles as a dimensionless constant times ℏ2/(meaB5), where aB is the Bohr radius. When an elastic platelet is perturbed from its equilibrium position, the restoring forces near a contact point (joined edge) are exceptionally large so that an appropriate boundary condition is that the platelet is cantilevered. Shearing forces cause the platelet to bend like a cantilevered beam with distributed electrostatic restoring forces. Solution for the platelet deformation leads to estimates of the shear modulus and shear speed, which compare favorably with existing data. [Work partially supported by the ONR and NSWC PCD.]
Laboratory measurements of sound speed and attenuation in water-saturated sand and glass beads.
Authors: Argo Theodore F. , Wilson Preston S.
Published: July 2011

The exact nature of sound propagation in water-saturated granular sediments, across the range of frequencies of interest in underwater acoustics, remains insufficiently understood. Well-controlled laboratory measurements are useful for validation and continued development of predictive models. Toward this end, a time-of-flight technique operating in the 250 kHz–750 kHz range was used to determine the sound speed and attenuation in a variety of artificial sediments including sand and glass beads of varying grain size and varying levels of homogeneity. Measurements will be presented and compared to existing model predictions.
Psychoacoustic limitations of discrete infinite impulse response and finite impulse response auralizations.
Authors: Mooney Jon W.
Published: July 2011

Auralizations based on discrete infinite impulse response (DIIR) filters having coefficients derived from statistical reverberation type analyzes are relatively quick and easy to produce but have limitations. Auralizations of very small rooms, or very large rooms having little acoustic treatment, or rooms having dissonant eigenmodes may sound less than real. Auralizations based on discrete finite impulse response (DFIR) filters having coefficients derived from finite element type analyzes can avoid these effects. In both DIIR and DFIR methods, filter coefficient spacing and polarity has a large effect on simulation quality. In this study, auralizations of a test room are created from recorded impulses, derived DFIRs and calculated DIIRs. Sound clips produced by each method are rated using audition and psychoacoustic measures of roughness, fluctuation and sharpness. This paper addresses (1) the derivation of DIIR based auralization from statistical reverberation analysis, (2) the derivation of DFIR based auralization from finite element analysis, (3) psychoacoustic limitations imposed on auralizations, and (4) DIIR/DFIR auralization limits indicated by audition and psychoacoustic rating of a limited number of simulation comparisons.
Trapping of sound in an open rectangular cavity.
Authors: Williams Duncan P. , Sargent Cristina V. , Skelton Elizabeth A.
Published: July 2011

The trapping of sound in a rectangular enclosure, such as a corridor or street, and the noise disturbance caused by trapping, can be a serious problem to understanding speech or other acoustic events. In contrast to confined systems that sustain so-called trapped modes, the behavior in a partially open enclosure is associated with leaky modes of the system that are “nearly” trapped but are still radiating some energy out of the system. This paper presents numerical modeling that has been developed to calculate the sound that can be nearly trapped in an open rectangular cavity such as the rectangular cross-section of a street canyon that is excited by a number of sources switching on and off. The cavity is surrounded by an elastic half space, i.e., surrounded on three sides by absorbing walls, for which it is necessary to implement a set of numerical grids that are staggered in space and in time. Results are shown for combinations of different walls and different shaped geometries that minimize the radiation losses out of the cavity. The results are used to comment on the problems that can be caused by the trapping of sound in acoustic systems.
Application of the mirror source method for sonic booms outdoors.
Authors: Lind Amanda B. , Sparrow Victor W.
Published: July 2011

Image source theory is commonly applied in architectural acoustic modeling and auralization software, with particular utility in prediction of early reflections. Here, image theory has been employed to model specular reflections of low amplitude sonic booms in outdoor environments. Mechel’s presentation of image source theory, the mirror source method (MSM), was implemented and tailored to outdoor environments and plane wave incidence. Given the low-frequency nature of the incident sonic booms, and the high-pass filtering associated with specular reflection from a finite surface, the frequency content of each specular reflection is of particular importance. The specular reflection impulse response (IR) is generated in two steps. First, the MSM is applied to obtain the arrival times and amplitudes of specular reflections, populating the initial IR. Next, each specular reflection is filtered, compensating for the finite size of the reflector. The magnitude response of the minimum phase filter is approximated by the frequency content reflected by a similar finite disk. [Work sponsored by the FAA through the PARTNER Center of Excellence and the Applied Research Laboratory at Penn State.]
How to get to Carnegie Hall: Real time signal processing.
Authors: Post Alexander E. , Cotter Shane , Catravas Palmyra
Published: July 2011

Since the acoustics of a practice room differ so greatly from a performance hall, it could be beneficial for musicians to prepare for a particular venue using a simulated version of that environment. The system described here makes use of a microprocessor and headphones to realize this virtual environment. The nominal room response is attenuated by the headphones, replaced by the response of the desired location. Usability goals include simplicity and portability, as well as the ability of the system to fade in to the background while in use, so that the user may focus on practice. We will report on the design and implementation of this system, the details of the real time processing system, and present measurements made to characterize the impulse response of practice rooms and performance halls. [Work supported from the National Science Foundation MRI 0923384 is gratefully acknowledged].
New Center for the Built Environment data reinforces poor acoustical performance of “green” office buildings.
Authors: Powell Kevin
Published: July 2011

Analysis by the US General Services Administration of new end-user-satisfaction data compiled by UC Berkeley’s Center for the Built Environment (CBE) continues to reinforce that green building interiors built according to the LEED Rating system suffer from a decline in acoustical performance. The facts are that occupants of offices that have been upgraded to achieve LEED certification express high levels of satisfaction with the Indoor Environmental Quality with one exception—acoustics. What is it about LEED-rated offices that causes this unintended consequence to occur? Is it because there are more reflective, hard surfaces causing reverberation? Or because the HVAC system has become quieter? Or because partition heights have been lowered to allow better airflow and more natural light, resulting in less privacy? Since increased occupant dissatisfaction may result in reduced productivity or increased absenteeism, GSA’s Office of Applied Research recently held an Acoustics Workshop in Washington DC to develop new guidelines for the construction of office environments that will eventually affect the GSA’s entire 8600-building portfolio.
Current and future acoustics credits in the leadership in energy and environmental design rating system.
Authors: Bruck Daniel C. , Salter Charles M. , Kurtz Alexis
Published: July 2011

The next version of LEED, currently in development, includes a new acoustics credit that is directed toward acoustical performance for all types of new construction projects. The credit includes performance requirements for background noise, speech privacy, sound isolation, sound reinforcement, and sound masking systems. As an acoustical performance credit for all types of new construction, the credit allows flexibility to address a wide range of performance criteria for various types of projects. This paper, coauthored by the acoustics working group within the U.S. Green Building Council, will present the intent, provisions, and background on the development of the new credit. A review of existing acoustics credits in LEED and approaches for compliance with existing credits will also be discussed.
Laboratory experimental investigation of the acoustical characteristics of vegetated roofs.
Authors: Connelly Maureen , Hodgson Murray
Published: July 2011

A laboratory-based experimental investigation was made of the sound-absorption and sound-transmission characteristics of vegetated roofs and/or their components. Impedance-tube measurements of the normal-incidence absorption coefficients of different substrates were related to their physical characteristics, finding that percentage organic matter, volumetric water content, and compaction are the key influencing factors. Spherical-decoupling-method measurements of the normal-incidence absorption coefficients of different thicknesses of substrate without and with vegetation showed that the absorption of substrates tends to increase with frequency, substrate depth, and to decrease with moisture content and vegetation. Sound-intensity measurements of the green roofs with different thicknesses of dry or wet substrate without and with vegetation, made in a purpose-built facility, showed that transmission loss increased rapidly with frequency, and increased with substrate depth and water content.
Optimization of silencers for interior natural ventilation openings.
Authors: Bibby Chris , Hodgson Murray
Published: July 2011

Naturally ventilated buildings are being constructed around the world due to advantages they offer in reduced HVAC operating costs, increased indoor air quality, and government subsidies for “green” construction and certification. Unfortunately, natural ventilation is often associated with a decrease in occupant acoustical satisfaction. One reason for this is the requirement to create acceptable air exchange rates in naturally ventilated buildings that have very limited pressure differentials; airflow paths must offer very low resistance. This leads designers to create paths by connecting adjacent spaces with apertures in the partitions or to use short transfer ducts rather than conventional duct systems. These apertures can be detrimental to the noise isolation provided by the partition. Products exist to attenuate noise through these apertures, but little exists in the literature about their performance. In this work, current methods and new methods of passively silencing interior natural ventilation openings have been evaluated and optimized using finite element simulations. To facilitate the optimization, silencer evaluation and selection criteria based on air flow and acoustical characteristics are proposed.
A regulatory approach to assessing the cumulative effects of anthropogenic noise and other stressors on endangered and threatened marine animals.
Authors: Johnson Craig
Published: July 2011

The U.S. Endangered Species Act of 1973 requires the U.S. National Marine Fisheries Service (NOAA-Fisheries) to assess the direct, indirect, interactive, and cumulative impacts of anthropogenic noise and other stressors on species that are listed as endangered or threatened under U.S. law. NOAA-Fisheries’ assessment method makes the cumulative impact component of these assessments more tractable by recognizing that individual organisms, populations, and species accumulate the effects of noise and other anthropogenic stressors differently. Assessing the cumulative impacts of noise and other anthropogenic stressors on the fitness of individuals remains the most critical and challenging component of these assessments. The concepts of canonical cost [McNamara and Houston, Am. Nat. 127, 358–378 (1986)] and vitality [Anderson, Ecology 70, 445–470 (2000)] currently provide the foundation for qualitative assessments of the cumulative impacts of stressors on individuals while the cumulative impacts of these stressors on populations and species are assessed using existing population viability and perturbation analyzes. Further development of the analytical methods associated with canonical costs and vitality would facilitate quantitative assessments of the cumulative impacts of noise and other anthropogenic stressors on endangered and threatened individuals, populations, and species.
The implications of long-term increases of anthropogenic noise on fish.
Authors: Popper Arthur N. , Casper Brandon M.
Published: July 2011

Most of the focus regarding environmental sound and fishes has been on (potential) effects of intense sounds such as pile driving and seismic air guns. There has been less concern, however, about the (potential) effects on fishes of less intense, but continuous increases in the overall noise environment in which fishes live. Such sources may include increased shipping in harbors, operations of off-shore wind farms, added noise in aquaculture facilities, etc. While the increase in ambient noise may be only a few decibels, such increases could have substantial effects on fishes resulting from the masking biologically relevant sounds and/or the overall acoustic scene. Moreover, and in contrast to intense sounds which generally ensonify any area for only a short period of time (e.g., sonar on a moving ship) or only ensonify relatively small areas (e.g., pile driving) that fish can leave, longer term sources may ensonify such large areas that many fish species cannot move from the area or would have to leave feeding and/or breeding sites in order to get to a quieter environment. This paper will review some data on potential effects of increased environmental sound on fishes and consider the long-term implications of this increase.
Effects of human-generated sounds on saltwater fish.
Authors: Conway Caitlin N. , Muller Mark W.
Published: July 2011

There is increasing apprehension of the potential adverse effects on marine mammals and fish caused by human-generated sounds. This study demonstrates the effects of low-frequency and high-frequency sounds on three spcies of fish, as such effects have been shown to be species specific. Three representative species from saltwater fish are chosen for this study. These species include Damselfish (Chrysiptera parasema), Clownfish (Amphiprion percula), and Molly fish (Poecilia sphenops). Ten of each species of fish are placed in a thirty gallon tank filled with water of the appropriate salinity level. The fish are monitored for one week in the absence of anthropogenic noise. The experiment portion consits of emitting short pulses of high-frequency sound waves and then long pulses of low-frequency sound waves over the fish for a predetermined duration. The fish are monitored for any changes in their behavior between each exposure of sound waves. This study may provide further insight into the effects of human-generated sounds on fish in their respective natural environments.
Noise exposure and acoustic behavior of beluga whales (Delphinapterus leucas) in an outdoor exhibit.
Authors: Hotchkin Cara F. , Parks Susan E.
Published: July 2011

Marine mammals are exposed to a wide variety of noise sources on a daily basis both in the wild and at zoos and aquaria. Filtration systems, aquarium visitors, and other anthropogenic sound sources (construction, road noise, weather, etc.) add noise to typically reverberant animal habitats in aquariums and zoos. Despite widespread concern about the effects of noise on behavior and welfare of wild marine mammals, there has been little research on the effects of chronic noise exposure on whales. This study used a single hydrophone system to characterize the acoustic environment, including noise and beluga whale vocalizations, in the Arctic Coast exhibit at Mystic Aquarium, a Division of Sea Research Foundation, Inc. between 28 October and 16 November 2010. Diel patterns in noise and beluga vocalizations, overlaps in call and noise frequencies, and general behavioral patterns were studied. Spatial variation in exhibit noise was also examined. Whale vocalizations had a distinct diel pattern, including changes in call rate and types during day and nighttime hours. Variations in noise levels were often associated with discrete events, including cleaning dives, filter backwash, and other exhibit maintenance.
Sealscarer induce behavioural responses of harbor porpoises (Phocoena phocoena).
Authors: Hschle Caroline , Brandt Miriam J. , Diederichs Ansgar , Betke Klaus , Nehls Georg
Published: July 2011

The construction of several wind parks in the North and Baltic Sea and the associated pile driving could negatively affect the only resident cetacean species, the harbor porpoise. We studied the efficiency of a Lofitech sealscarer that emits pulses at a main frequency of 14 kHz to temporarily deter harbor porpoises during construction periods in order to avoid physical injury. Reactions of harbor porpoises were studied by tracking the animals from a cliff 20 m above sea level using a theodolite. Six trials showed animals immediately disappearing after sealscarer activation of 300–700-m distance to the porpoise with no animal resurfacing within 1 km. A greater deployment distance of 1.2–2.6 km to the porpoise provoked immediate disappearance of two porpoises; four porpoises showed a clear avoidance reaction and change of swimming direction. Reactions of two animals were unclear and these consequently lost; one individual resumed with its normal behavior. These results show that the sealscarer caused porpoises to leave. However, the use of sealscarers cannot guarantee complete absence of porpoises within areas where noise from windfarm construction can potentially harm them since reactions possibly differ between, for example, individuals and/or motivational states.
Presence of harbor porpoises near a pile driving site and modeling of cumulative acoustic effects.
Authors: Lucke Klaus , Lepper Paul. A. , Daehne Michael , Siebert Ursula
Published: July 2011

The construction of the a small wind farm in the southern North Sea has just been completed. Possible effects on harbor porpoise (Phocoena phocoena) distribution and habitat use caused by the pile driving impulses emitted during the installation of the foundations for 12 offshore wind turbines (OWTs) were assessed by ship surveys, aerial surveys, and static acoustic monitoring (SAM). SAM data and sighting data revealed that during the pile driving activities for the construction of the transformer platform as well as for the first OWTs the presence of harbor porpoises decreased significantly. However, the number of porpoise detections by the SAM units increased during the pile driving activities toward the end of the construction period. Habituation, ecological parameters, and external effects are considered as potential reasons for this increased presence of harbor porpoises in the vicinity of the construction site. The cumulative acoustic energy received by the animals exposed to repeated pile driving impulses is modeled for different scenarios in order to assess potential negative auditory effects on the animals.
Measurements of ship noise and calling behavior on bioacoustic probes during opportunistic exposure of blue whales to commercial ship noise.
Authors: McKenna Megan F. , Oleson Erin M. , Goldbogen Jeremy A. , Calambokidis John
Published: July 2011

Bioacoustic probes were deployed on blue whales in and around commercial shipping lanes in Southern California. The proximity of shipping routes to predictable blue whale feeding grounds makes this an ideal location to study the impact of intense low-frequency noise on whale behavior. The bioacoustic probe is outfitted with a calibrated hydrophone, and records temperature, pressure, and two-axis acceleration, allowing us to evaluate sound exposure levels in relation to swimming and calling behaviors. During eight tag deployments, large commercial ships came within 1000 m or less of the tagged whale. Received levels of ship noise were measured from the tag to estimate the sound exposure levels. Because of the high level of flow noise recorded on the tag, measurements of ship noise were only possible at minimum velocity and speed. Dive and surface behaviors were evaluated related to the passage of the ship and elevated noise levels. One calling whale was tagged and exposed to ship noise at a close approach; no major change in calling behavior was observed. The results of this research provide insight on blue whale response to ships and highlight some of the challenges when measuring low frequency noise from an attached tag. [This work was supported by the ONR.]
Southeast Alaska Sperm Whale Avoidance Project: Collaboration among fishermen, acousticians, biologists and managers to reduce longline depredation in the Gulf of Alaska.
Authors: Straley Janice , Thode Aaron , O'Connell Victoria , Behnken Linda , Folkert Kendall , Mesnick Sarah , Lunsford Chris
Published: July 2011

In the eastern Gulf of Alaska, depredation of demersal longline fishing gear set for sablefish (Anoplopoma fimbria) by sperm whales (Physeter macrocephalus) has occurred since at least the mid-1970s. In 1995, with the implementation of Individual Fishing Quotas, the season expanded from a 2 week derby style fishery to 8 months. This change allowed more opportunity for whales to depredate longline gear and reports of depredation increased resulting in economic loss to the fleet. Beginning in 2003, the North Pacific Research Board funded a collaborative study among fishermen, scientists, and managers to collect quantitative data on longline depredation. The goal of the Southeast Sperm Whale Avoidance Project (SEASWAP) is to determine the mechanics of the depredation, characterize the whales involved, and to recommend changes in fishing behavior to reduce depredation. The longline fleet provided fishing data and allowed researchers to collect behavioral, genetic, and acoustic data in conjunction with their fishing operations. Through this effort, SEASWAP has estimated numbers and sexes of depredating whales, identified long-range acoustic cues that attract animals to the gear, and systematically tested various depredation reduction strategies, including decoy deployments, active playbacks, and modifications to fishing gear.
Development of an acoustic-based toothed whale depredation detection system for longline fisheries.
Authors: McPherson Geoff , Clarke Gary , Hingley Brian , McPherson Craig , Erbe Christine
Published: July 2011

Depredation on baited hooks and catch of longline fishing gear by toothed whales is a serious source of fishery product loss and increased operating costs. Depredation in tropical waters is dominated by false killer, short fin pilot, and melon headed whales. Depredation is associated with increased acoustic communication, both echolocation and whistles. Longlines take many hours to set and haul over tens of kilometers. Depredation detection would assist operators make decisions to reduce fishery loss. Termination of setting when depredation was occurring on recently set gear, or hauling sections of gear where depredation had not as yet occurred, would help reduce losses. Depredation avoidance would reduce risk of bycatch. Global Detection Systems is developing a depredation proximity detector. A GPS-based and web-enabled buoy will indicate locations of the buoys on the line. Detection is by a sensor array developed for fishing vessels. Detection, irrespective of the toothed whale species involved within a radius of the buoy, will be processed on-board the buoy using an entropy based detection system [Erbe, C., J. Acoust. Soc. Am. 127, 1959 (2010)]. The radius of detection is being determined in fishery trials in Australian and Central Pacific waters. [Work supported by AusIndustry and Commercialisation Australia.]
Assessment of specialized acoustic pingers to mitigate toothed whales depredation on Japanese tuna longline catches in the Central Pacific.
Authors: Nishida Tom , McPherson Geoff
Published: July 2011

Schemes to mitigate depredation by toothed whales (mainly killer and false killer whale) on industrial tuna longline operations have existed for over half a century in all major Oceans. We have assessed a range of avoidance and passive acoustic methods, some currently being further developed by industry. In 2010 using four longline vessels we tested the effectiveness of the newly developed dolphin deterrent device (DDD) pinger model suited for longline depredation and the dolphin interactive device (DiD) pinger manufactured by STM Products Inc. (Italy) in the high depredation area off south of Hawaii. Applying the experimental design, we investigated if DDD and DiD were statistically effective to reduce depredation. Preliminary assessment suggested that depredation rates on longline catches were probably reduced with DDD pingers and also with the interactive DiD pingers. Interactive and variable output mitigation pingers are important to prolong effectiveness as would be their capability to function with other mitigation techniques. Effectiveness of pingers in a fishery context may be based on economic significance (increased returns and reduced losses) as against statistical significance. [This project was funded by Fisheries Research Agency of Japan.]
Depredation of striped dolphin on squid fishery and behavioural responses to interactive pinger.
Authors: Buscaino Giuseppa , Bellante Antonio , Buffa Gaspare , Filiciotto Francesco , Maccarrone Vincenzo , Di Stefano Vincenzo , Tranchida Giorgio , Mazzola Salvatore
Published: July 2011

The depredation of dolphins on some artisanal fisheries in the Mediterranean Sea is the major source of economic loss. This study aims to reveal the behavior of striped dolphin during interaction with flying squid fishery equipped with interactive pinger in the Ionian Sea (southern Italy). A four channel acoustics acquisition system was used during fishing hauls to record the clicks and to localize the positions of dolphins through the time delay of arrival method. The preliminary analysis shows that dolphins approached the artificial light, used for attract the squids, diving further on 100 m below the fishing boat. The number and the power of dolphins’ clicks decreased after the signals emitted by the interactive pinger. The distances of dolphins from fishing boat do not seem change significantly before and after pinger emissions. Although the efficiency of DDD pingers to decrease the depredation level was demonstrated in some study, the functioning mechanism is still unknown. Our data could indicate that pinger works to reducing the dolphin’s sonar activities.
Depredation mitigation of bottlenose dolphins on coastal and oceanic set net and line based fisheries by dolphin dissuasive device and dolphin interactive dissuasor pingers.
Authors: Finezzo Alessandro , Ipuche Martin
Published: July 2011

Depredation by marine mammals on coastal and oceanic net and line based fisheries is a major source of economic loss to fisheries where by-catch levels are low. To further minimize possible habituation to DDD pingers that feature variable (frequency and amplitude) signals an interactive model, the DiD, was designed. The DiD reacts to broadband frequency clicks comparable to delphinid clicks. The detection sensitivity is about 130 dB re 1 μ Pa at 1 m at the minimum threshold. The sensitivity curve matched peak output of dolphin clicks, particularly those of larger toothed whales responsible for depredation, achieving minimization of snapping shrimp interference in shallow water fishery applications. The DDD and DiD output’s were changed to improve their effectiveness resulting in modulated tones and pseudo echolocation signals. Trials with dolphins in gillnet fisheries indicated DiD spacing could be 300 m. Spacing may change slightly with environment and fishery. DDD offers a reliable method for mitigating by-catch. DiD offers a choice to address long term effectiveness of pingers for depredation mitigation with limitation of power requirements, restriction of sound exposure in sensitive environments, and with benefits to industry and the environment. [Work supported by CNR, SeaMed, IAMC, Trapani, Italy.]
Acoustic pingers to mitigate dolphin bycatch and depredation, barely a one third octave between them.
Authors: McPherson Geoff , Gribble Neil
Published: July 2011

Bycatch mitigation alarms/pingers for dolphins/porpoises and whales are developed in the mid 1980s in Japan and Canada, respectively. Alarms are attached to nets so the acoustic warning is associated with the obstruction, avoided, and the behavior reinforced via associative learning. A continuous association between alarms (the warning) and a net (the obstruction) is essential. What constitutes an appropriate alarm is not fully understood but should result in reduced entanglement in fishery conditions, irrespective of the mammals behavior observed by human observers. Dolphins are rarely deterred with bycatch pingers; they are alerted if they were inattentive but often maintain a close association with nets. Both bycatch and depredation may be reduced. These puzzling results should be investigated. At the other end of the pinger cline are the pingers that move dolphins from the vicinity of nets or lines to mitigate depredation, and by default, bycatch. The mechanisms are not known how these pingers can be successful at sound pressure levels comparable to dolphin whistles yet the results are becoming clear. The avoidance behavior from these pinger types should be investigated with captive animals. Interactive pingers and net material/reflectors with higher target strength are also seen as other important developments.
The Naval Postgraduate School Ocean Acoustic Observatory: Past experiences and current proposition.
Authors: Chiu Ching-Sang , Miller Christopher W. , Colosi John A.
Published: July 2011

The Naval Postgraduate School (NPS) Ocean Acoustic Observatory (OAO) utilized a cabled hydrophone array of the decommissioned Integrated Undersea Surveillance System (IUSS) Naval Facility at Point Sur, CA. Established in 1993, the NPS OAO became the prototype dual-use IUSS facility to release data to the education and research communities. The cable severed in January 2001 and was deemed unrepairable during a 2004 attempt. In this paper, scientific results from several of the research activities between 1993 and 2000 are presented. Some of these research projects were conducted in partnership with external academic institutions and some conducted solely by NPS investigators. Past research activities include signal propagation studies, acoustical thermometry and tomography, and ambient sound and whale monitoring. Since 2006, suboptimal monitoring efforts have continued using duty-cycled recordings from a moored hydrophone, lacking real-time access and continuity. Finally, a proposal to replace the existing terminal equipment building and install a new high-bandwidth cable terminating with an undersea distributed node seaward to enable emerging multifaceted, multidiscipline naval and academic research, developments, and applications is described. With strong endorsements by the NPS Dean of Research and Undersea Warfare Chair, among others, this dual-use plan has been submitted as a Military Construction project.
Interfacing a scientific echosounder with a cabled ocean observatory.
Authors: Barbee David H. , Horne John K. , Urmy Samuel S. , Kreisberg Richard B.
Published: July 2011

To demonstrate the utility of adding active acoustics to ocean observatories, an upward-looking, 38 kHz Simrad EK-60 echosounder package was connected to the Monterey Accelerated Research System (MARS) Observatory. The Deepwater Echo Integrating Marine Observatory System (DEIMOS) integrated the echosounder with commercial electrical and communications hardware in a glass pressure sphere, all mounted in an ROV-deployable frame. A cabled connection to the MARS node provided instrument power and real-time TCP/IP network communications to surface control and display systems. DEIMOS sampled the entire water column (875 m) at 0.2 Hz from February 27, 2009 to August 18, 2010. The instrument collected 50 Mbytes of raw data every 3 h resulting in a total of 167 Gbytes of raw data. Metrics developed to quantify distributions and abundances of pelagic organisms show temporal variability over seasons, diel cycles, and minute-to-minute predator-prey interactions. We will present design goals, deployment challenges, and operational experiences including in situ calibration and interactions with other instruments. Active acoustics is a vital and viable component of ocean observatories.
Spatial characteristics of an Arctic ambient noise field.
Authors: Sagen Hanne , Tollefsen Dag , Sandven Stein , Tveit Elling
Published: July 2011

During multidisciplinary experiments in the 1980s and 1990s, ambient noise characteristics were found to be related to different ice types, distance from the ice edge, tidal current, wave conditions, and ice edge eddies. Primary noise generation mechanisms are ice floe collisions, ice cracking, ridging, and breakup caused by wave interaction with sea ice, internal ice stress, and changes in air temperature. Furthermore, sound propagation conditions determined by surface reflectivity due to sea ice and ocean stratification have a strong impact on the time averaged ambient noise spectrum. Ambient noise as a way to provide information about the environment is being explored in ongoing experiments within the ACOBAR and WIFAR projects. This paper presents spatial characteristics of the low-frequency ambient noise field from data collected simultaneously at 16 sites in the Marginal Ice Zone (Fram Strait) in October 2010. The acoustic measurements covered a 100 x 100 km2 area from open water to within the ice cover at frequencies from 10 Hz to 2 kHz. Noise spectra will be presented and compared with earlier measurements from the same area.
A method for extracting ocean sound absorption from ambient noise measurements.
Authors: Paddock Joel , Siderius Martin
Published: July 2011

This paper investigates a method for estimating the sound absorption of an ocean environment using passively measured ambient noise. Theory predicts that the level of absorption has a measurable effect on bottom loss estimation using ambient noise. An initial estimate of the absorption is obtained from this method, and is then refined through parametric optimization by comparing the measured data to a forward model of the ambient noise. The proposed method uses a passive sensor array which does not require extra sound energy to be projected into the ocean environment. Since the noise data consist of cross-correlations between sensors at individual frequencies, it is inherently spatially averaged so that the estimated absorption is potentially less sensitive to small scale fluctuations than methods that compare signal amplitudes over long propagation paths. The low frequency (less than 1 kHz) sound absorption mechanism of ocean water is dominated by the chemical relaxation of boric acid, the concentration of which is dependent on ocean pH levels. An estimate of ocean sound absorption could be valuable in tracking ocean acidity. The theoretical approach will be tested using simulated noise fields. Preliminary results using measured ambient noise will also be presented. [Work suppported by ONR Ocean Acoustics.]
Comprehensive Nuclear Test Ban Treaty monitoring: The hydroacoustic network and its applications.
Authors: Forbes Andrew M. , Haralabus Georgios
Published: July 2011

In the 14 years since the Comprehensive Nuclear Test Ban Treaty was signed, a network of 262 International Monitoring System (IMS) stations (mostly seismic) has been constructed out of a planned total of 337 facilities. 11 are hydroacoustic stations, of which six use hydrophones and five use T-phase seismometers. While the hydroacoustic network’s primary purpose is to detect, locate, and identify underwater explosions, a secondary benefit is civil and scientific applications of the data. Given the ocean’s remarkable transparency to low-frequency sound, it is not surprising that the hydrophone stations detect many other events and activities, e.g., marine mammal vocalizations, iceberg calving, underwater volcanoes, and seismic exploration. A variety of scientific studies have already used CTBTO hydroacoustic data, and the new virtual Data Exploitation Center (vDEC) is designed to facilitate and encourage more studies. Tsunami warning centers in eight countries around the world now receive real-time seismic and hydroacoustic data from the CTBTO. Future applications include ocean climate studies using acoustic thermometry, taking advantage of the permanency of the installed hydrophones and the repeatability of sources of opportunity, such as seismic exploration airguns. The challenge of sustaining the hydroacoustic network for decades must not be underestimated, however.
Hydrophones for surface mapping of high-intensity transducers.
Authors: Keilman George W. , Morrison Kyle P.
Published: July 2011

In order to fully characterize transducers used in high-intensity focused ultrasound, it is useful to measure the source field at the transducer’s radiating surface while the transducer is radiating into water. A new, ruggedized hydrophone has been recently developed to enable direct-contact scanning at the radiating surface without damage to the source transducer. The hydrophone enables the acquisition of high-resolution images of the source fields for single-element and array transducers. This allows beam features such as unexpected side lobes or other anomalies to be traced back to local conditions at the radiating surface. The compact size of the hydrophone also allows source field measurements to be made in the presence of reflective structures located within the field of the transducer. This hydrophone is useful in the testing of transducer quality. In array transducers, it is also useful in verifying the geometric locations, radiating areas, and channel numbering of array elements, and in the measurement of channel-to-channel crosstalk.
Measurement of focal peak intensity generated by high intensity focused ultrasound transducers.
Authors: Civale John , Rivens Ian , ter Haar Gail
Published: July 2011

High intensity focused ultrasound (HIFU) is a technique that is gaining widespread acceptance as a tumour treatment modality. Calibration of HIFU transducers poses a number of challenges, one of which is the need to measure the intensity generated at the focal peak. This quantity can be estimated by measuring the acoustic pressure using a calibrated hydrophone, but measurements are typically made at low drive powers in order to avoid damage to the sensor. An alternative is to use a radiation force or other techniques to measure the total power in the beam; estimation of the intensity at the focal peak is then ordinarily achieved with knowledge of the lateral 6 dB beam width together with assumptions about the shape of the focused beam. These underlying assumptions, however, may not be strictly valid, thus leading to overestimation of the focal peak intensity, particularly where the transducer contains a central hole for imaging. This paper will present results from simulations and hydrophone scans, which demonstrate the relationships between the spatially integrated (total power), averaged (−6 dB), and focal peak intensities. This information will be used to demonstrate possible strategies for determination of focal peak intensities from acoustic power measurements with improved confidence.