ATI Technical Training Short Course Underwater Acoustics for Biologists and Conservation Managers: A comprehensive tutorial designed for environmental professionals
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Underwater Acoustics for Biologists and Conservation Managers: A comprehensive tutorial designed for environmental professionals. This three-day course is designed for biologists, and conservation ...

Underwater Acoustics for Biologists and Conservation Managers: A comprehensive tutorial designed for environmental professionals. This three-day course is designed for biologists, and conservation managers, who wish to enhance their understanding of the underlying principles of underwater and engineering acoustics needed to evaluate the impact of anthropogenic noise on marine life. This course provides a framework for making objective assessments of the impact of various types of sound sources. Critical topics are introduced through clear and readily understandable heuristic models and graphics.

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ATI Technical Training Short Course Underwater Acoustics for Biologists and Conservation Managers: A comprehensive tutorial designed for environmental professionals ATI Technical Training Short Course Underwater Acoustics for Biologists and Conservation Managers: A comprehensive tutorial designed for environmental professionals Presentation Transcript

  • Professional Development Short Course On: Underwater Acoustics for Biologists and Conservation Managers Instructors: Dr. William T. Ellison Dr. Orest Diachok ATI Course Schedule: http://www.ATIcourses.com/schedule.htm ATI's Underwater Acoustics for Biologists: http://www.aticourses.comunderwater_acoustics_for_biologists_and_conservation_managers.htm
  • Underwater Acoustics for Biologists and Conservation Managers A comprehensive tutorial designed for environmental professionals NEW! Summary This three-day course is designed for biologists, and conservation managers, who wish to enhance their understanding of the underlying principles of June 15-17, 2010 underwater and engineering acoustics needed to Silver Spring, Maryland evaluate the impact of anthropogenic noise on marine life. This course provides a framework for making $1590 (8:30am - 4:30pm) objective assessments of the impact of various types of sound sources. Critical topics are introduced through "Register 3 or More & Receive $10000 each clear and readily understandable heuristic models and Off The Course Tuition." graphics. Course Outline Instructors 1. Introduction. Review of the ocean Dr. William T. Ellison is president of Marine Acoustics, anthropogenic noise issue (public opinion, legal Inc., Middletown, RI. Dr. Ellison has over findings and regulatory approach), current state 45 years of field and laboratory experience of knowledge, and key references summarizing in underwater acoustics spanning sonar scientific findings to date. design, ASW tactics, software models and biological field studies. He is a graduate of 2. Acoustics of the Ocean Environment. the Naval Academy and holds the degrees Sound Propagation, Ambient Noise of MSME and Ph.D. from MIT. He has Characteristics. published numerous papers in the field of acoustics and is a co-author of the 2007 monograph Marine Mammal 3. Characteristics of Anthropogenic Sound Noise Exposure Criteria: Initial Scientific Sources. Impulsive (airguns, pile drivers, Recommendations, as well as a member of the ASA explosives), Coherent (sonars, acoustic modems, Technical Working Group on the impact of noise on Fish depth sounder. profilers), Continuous (shipping, and Turtles. He is a Fellow of the Acoustical Society of offshore industrial activities). America and a Fellow of the Explorers Club. 4. Overview of Issues Related to Impact of Dr. Orest Diachok is a Marine Biophysicist at the Johns Hopkins University, Applied Physics Laboratory. Dr. Sound on Marine Wildlife. Marine Wildlife of Diachok has over 40 years experience in acoustical Interest (mammals, turtles and fish), Behavioral oceanography, and has published Disturbance and Potential for Injury, Acoustic numerous scientific papers. His career has Masking, Biological Significance, and Cumulative included tours with the Naval Effects. Seasonal Distribution and Behavioral Oceanographic Office, Naval Research Databases for Marine Wildlife. Laboratory and NATO Undersea Research Centre, where he served as Chief 5. Assessment of the Impact of Scientist. During the past 16 years his work Anthropogenic Sound. Source characteristics has focused on estimation of biological parameters from (spectrum, level, movement, duty cycle), acoustic measurements in the ocean. During this period Propagation characteristics (site specific he also wrote the required Environmental Assessments for character of water column and bathymetry his experiments. Dr. Diachok is a Fellow of the Acoustical Society of America. measurements and database), Ambient Noise, Determining sound as received by the wildlife, absolute level and signal to noise, multipath What You Will Learn propagation and spectral spread. Appropriate • What are the key characteristics of man-made metrics and how to model, measure and sound sources and usage of correct metrics. evaluate. Issues for laboratory studies. • How to evaluate the resultant sound field from 6. Bioacoustics of Marine Wildlife. Hearing impulsive, coherent and continuous sources. Threshold, TTS and PTS, Vocalizations and • How are system characteristics measured and calibrated. Masking, Target Strength, Volume Scattering and Clutter. • What animal characteristics are important for assessing both impact and requirements for 7. Monitoring and Mitigation Requirements. monitoring/and mitigation. Passive Devices (fixed and towed systems), • Capabilities of passive and active monitoring and Active Devices, Matching Device Capabilities to mitigation systems. Environmental Requirements (examples of From this course you will obtain the knowledge to passive and active localization, long term perform basic assessments of the impact of monitoring, fish exposure testing). anthropogenic sources on marine life in specific ocean environments, and to understand the uncertainties in 8. Outstanding Research Issues in Marine your assessments. Acoustics. Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805 Vol. 102 – 11
  • e e at at lic l ia om lic up er .c up at D es D IM ot rs ot N om AT ou N o Ic o D .c • AT l • D l ia www.ATIcourses.com es te l• er rs a ia w. a ic at om er w ri ou pl M w ate .c at Ic u TI D es M M Boost Your Skills •A ot rs TI 349 Berkshire Drive I AT w. N ou A te Riva, Maryland 21140 AT with On-Site Courses w Do Ic te • .c ca Telephone 1-888-501-2100 / (410) 965-8805 te om es li ca l• om a rs up Tailored to Your Needs Fax (410) 956-5785 w .c lic ia w. li ou D Email: ATI@ATIcourses.com w up er es up AT Ic ot at w D rs D AT N M The Applied Technology Institute specializes in training programs for technical professionals. Our courses keep you ot ou ot o current in the state-of-the-art technology that is essential to keep your company on the cutting edge in today’s highly N I Ic N w. D AT competitive marketplace. Since 1984, ATI has earned the trust of training departments nationwide, and has presented o AT Do l• D on-site training at the major Navy, Air Force and NASA centers, and for a large number of contractors. Our training ia l• increases effectiveness and productivity. Learn from the proven best. w. • er w ial ia w at er w er For a Free On-Site Quote Visit Us At: http://www.ATIcourses.com/free_onsite_quote.asp IM at at IM AT IM For Our Current Public Course Schedule Go To: http://www.ATIcourses.com/schedule.htm w AT AT
  • Introduction • Student Introduction • Identify key Interests of Students • Course Objectives – Introduction to Marine Mammals from an Acoustic Viewpoint • their sounds & hearing and • how they are affected by and respond to anthropogenic sounds – Methods and Tools for Bioacoustic Issues • Metrics • Examples of past/present research (may do last!) – Bowhead Whales in the Arctic (1980’s) – SOCAL SRP Tagged Fin Whale (1990’s) – Stellwagen Bank NOPP (Today) W – Tools and Concepts for Evaluating Impacts on the Marine Environment • Life Cycle Approach to Environmental Compliance (EC) • The Utility of Modeling as an EC Tool • Assessment Techniques
  • Key Reference Material • Southall, et al. 2007, Marine Mammal Noise Exposure Criteria: Initial Scientific Recommendations • Richardson, et al.1995, Marine Mammals and Noise • Urick, (any ed.) Principles of Underwater Sound for Engineers • Harris (ASA Reprint) Handbook of Acoustical Measurements and Noise Control • Crocker (ASA Pub), Encyclopedia of Acoustics • Kryter (any ed.) The Effects of Noise on Man • Bregman, Acoustic Scene Analysis, MIT Press • ANSI STD’s – ANSI S12.7 – Methods for measurement of impulse noise – ANSI S1.1 – Acoustical Terminology – ANSI S1.42 – Acoustic Weighting Networks • NRC Reports – 2000 Marine Mammals and Low Frequency sound – 2003 Ocean Noise and Marine Mammals – 2005 Marine Mammal Populations and Ocean Noise: Determining when Noise causes Biologically Significant Effects
  • Part I - Introduction to Marine Mammals from an Acoustic Viewpoint* *Primary Reference is Southall, et al. 2007 *Primary Reference is Southall, et al. 2007
  • Mystery Sound
  • Whale Sounds & Videos {Separate Media}
  • Marine Mammal Hearing o One of the major accomplishments in [Southall, 2007] was the derivation of recommended frequency-weighting functions for use in assessing the effects of relatively intense sounds on hearing in some marine mammal groups. It is abundantly clear from: o measurements of hearing in the laboratory, o sound output characteristics made in the field and in the laboratory, and o auditory morphology o that there are major differences in auditory capabilities across marine mammal species (e.g., Wartzok & Ketten, 1999). o Most previous assessments of acoustic effects failed to account for differences in functional hearing bandwidth among marine mammal groups and did not recognize that the ‘nominal’ audiogram might be a relatively poor predictor of how the auditory system responds to relatively strong exposures.
  • Marine Mammal Hearing • [Southall, 2007] delineated five groups of functional hearing in marine mammals and developed a generalized frequency-weighting (called “M- weighting”) function for each. • The five groups and the associated designators are: – (1) mysticetes (baleen whales), designated as “low- frequency” cetaceans (Mlf); – (2) some odontocetes (toothed whales) designated as “mid- frequency” cetaceans (Mmf); – (3) odontocetes specialized for using high frequencies, i.e., porpoises, river dolphins, Kogia, and the genus Cephalorhynchus (Mhf); – (4) pinnipeds, (seals, sea lions and walruses) listening in water (Mpw); and – (5) pinnipeds listening in air (Mpa).
  • Frequency Weighting “In assessing the effects of noise on humans, either an A- or C-weighted curve is applied to correct the sound level measurement for the frequency-dependent hearing function of humans. Early on, the panel recognized that similar, frequency-weighted hearing curves were needed for marine mammals; otherwise, extremely low- and high-frequency sound sources that are detected poorly, if at all, might be subject to unrealistic criteria.” Southall et al. (2007). Figure 3.1a below illustrates the A-, B- and C-weighting curves for human hearing (Harris, 1998, Figure 5.17). Weighting Curves Weighting Curves for Human Hearing for Human Hearing Metrics. Metrics. C-Filter is used as C-Filter is used as Functional Basis for Functional Basis for the M-Weighting the M-Weighting Filter for Marine Filter for Marine Mammals Mammals
  • M-Weighting Southall, 2007 - -For injury Southall, 2007 For injury assessment, behavior not assessment, behavior not addressed. Issue! addressed. Issue! For Marine Mammal For Marine Mammal Hearing Metrics: same Hearing Metrics: same mathematical structure mathematical structure as the C-weighting as the C-weighting used in human hearing, used in human hearing, Odontocetes Mysticetes
  • M-Weighting The M-weighting Southall, 2007 developed for the five functional marine mammal hearing groups has the same mathematical structure as the C-weighting used in human hearing, which reflects the fact that sounds must be more intense at high and low frequencies for them to be perceived by a listener as equally loud. This weighting is most appropriate determining the effects of intense sounds, i.e., those with equal loudness to a tone 100 dB above threshold at 1000 Hz. The M-weighting was designed to do much the same for the different marine mammal groups with the only difference being the low- and high-frequency cutoffs. The M-weighting for marine mammals, like the C-weighting used in humans, rolls off at a rate of 12-dB per octave. The general expression for M-weighting [M(f)], using estimated frequency cut- offs for each functional marine mammal hearing group, is given as: R( f ) M ( f )  20 log10 (7) eq. max{ R( f ) } 2 2 f high f R( f )  ( f 2  f high )( f 2  f low ) 2 2 (8) eq. The estimated lower and upper “functional” hearing limits are designated (flow and fhigh) for each of the five functional marine mammal hearing groups
  • M-Weighting (Application) The application of M- -9dB Weighting is most easily conceived of as a simple filter. For example, if a Hi-Freq Cetacean was exposed to a sound at 100Hz, the effective level for assessment purposes could be reduced by 9dB. 100 Hz
  • Part II - Methods and Tools for Bioacoustic Issues & Analysis
  • Bioacoustic metrics and field work Sound source characterization – Sound Types • Pulsed • Non-Pulsed • Continuous – Issues include: • Effective SL as most are not point sources (SL=RL+TL) • Energy (Time integration), Peak, RMS??? • Band measurements (M-Filter, 1/3 Octave….)
  • Sound source characterization • Sound Types need to be broken down in categories: – Pulsed – Non-Pulsed – Continuous • Why? – Experience has shown that these sound types result in different effects for both injury and behavior – Need different metrics like: • SEL, • Peak Pressure or RMS, • Freq. Weighting, • Barotrauma (Acoustic impulse Pa-Sec)
  • Pulse vs. Non-Pulse* •The term PULSE is used here to describe brief, broadband, atonal, transients (ANSI 12.7, 1986; Harris, Ch. 12, 1998), which are characterized by a relatively rapid rise time to maximum pressure followed by a decay that may include a period of diminishing and oscillating maximal and minimal pressures. Examples of pulses are explosions, gunshots, sonic booms, seismic airgun pulses, and pile driving strikes. •NON-PULSE (intermittent or continuous) sounds can be tonal, broadband, or both. They may be of short duration, but without the essential properties of pulses (e.g., rapid rise-time). Examples of anthropogenic, oceanic sources producing such sounds include vessels, aircraft, machinery operations such as drilling or wind turbines, and many active sonar systems. As a result of propagation, sounds with the characteristics of a pulse at the source may lose pulse-like characteristics at some (variable) distance and can be characterized as a non-pulse by certain receivers. (This last is a key issue to be analyzed) *As defined in Southall, 2007 Criteria Paper
  • Metrics Peak sound pressure is the maximum absolute value of the instantaneous sound pressure during a specified time interval and is denoted as Pmax in units of Pascals (Pa). It is not an averaged pressure. Peak pressure is a useful metric for either pulses or non-pulse sounds, but it is particularly important for characterizing pulses (ANSI 12.7, 1986; Harris, Ch. 12, 1998). Because of the rapid rise-time of such sounds, it is imperative to use an adequate sampling rate, especially when measuring peak pressure levels (Harris, Ch. 18, 1998). mean-squared pressure (rms) is the average of the squared pressure over some duration. For non-pulse sounds, the averaging time is any convenient period sufficiently long to permit averaging the variability inherent in the type of sound. To be applied with care to pulse sounds SPL - Sound pressure levels are given as the decibel (dB) measures of the pressure metrics defined above. The root-mean-square (rms) sound pressure level (SPL) is given as dB re: 1 µPa for underwater sound and dB re: 20 µPa for aerial sound. Peak sound pressure levels (hereafter “peak”) are given as dBpeak re: 1 µPa in water and dBpeak re: 20 µPa in air. Peak-to-peak sound pressure levels (hereafter “peak-peak”) are dBp-p re: 1 µPa in water and dBp-p re: 20 µPa in air.
  • Metrics Sound exposure level (SEL) is the decibel level of the cumulative sum-of-square pressures over the duration of a sound (e.g., dB re: 1 μPa2-s) for sustained non-pulse sounds where the exposure is of a constant nature (i.e., source and animal positions are held roughly constant), . For pulses and transient non-pulse sounds, it is extremely useful because it enables sounds of differing duration to be related in terms of total energy for purposes of assessing exposure risk. The SEL metric also enables integrating sound energy across multiple exposures from sources such as seismic airguns and most sonar signals.  N T 2     pn (t ) dt   n 1 0  SEL  10 log10  2   p ref     
  • Source Characterization (SL) • Distributed sources (arrays) require special consideration – Major issue in understanding near field exposure for large aperture arrays such as LFA and seismic (early point of contention!) – Modeling requires near/far field analysis – Particle velocity considerations (seismic example) A Tool that engineers A Tool that engineers can bring to the table! can bring to the table!
  • SL in the Near field/Far field Regions [RN-RC ]< /4 SL=SLE+20Log(NFF) where: RN = [RC2+HN2]1/2 NFF = # of elements in the HN Far Field RC Far Field Criteria for a Vertical Line Array of Sources: RFF = RC SLE = SL of when [RN-RC ]< /4 ea element
  • 2. Near Field Receive Level Analysis - The analysis required to evaluate the near field of a VLA source can be easily accomplished by replacing each nth element of the N element array with an equivalent point source,1 Pn[R] = {PE/|R-Rn|}{cos(k|R-Rn|) + i sin(k|R-Rn|)} (3) where, PE = 10exp[SLE/20] (4) The resultant pressure, P[R] at the field point R is given by: P[R] =  Pn[R], n=1,N (5) Note that this is a complex term, and the resultant receive level value, RL in dB, can be arrived at by taking: RL=20Log(|P[R]|) (6) The difference, RL, between that value and that approximated by simple spherical spreading from the center of the array using the far field SL is given by: RL= RL-[SL-20Log(|R|)] (7) The geometry used to evaluate the VLA and relevant coordinate system is shown in Figure 1 along with an example for an array of 4 elements. R = xiX + yiY + ziZ (8) 1 M.C. Junger, D.L. Feit, Sound, Structures, and Their Interaction, MIT Press, Cambridge, 1972, Section 3, Applications of the Elementary Acoustic Solutions, et seq.
  • nth Z element R-R Y Fig 1: Cartesian n Coordinate System With example showing an N element VLA with spacing=d zn  R z iY d iZ r  X iX R=xiX+yiY+ziZ R= zniZ x=rcos() y=rsin() z=Rcos( r=Rsin(
  • Subaperture Shortcut to Array Near-Field Effects The near field value can also be evaluated in an approximate way by determining the far field range of each of the embedded subapertures in the array. For example, the far field range for array subapertures from 4 elements to 18 is shown in Table 2-1: Table 2-1 Subaperture Far Field Effects No. Elements Rff 20Log(N/Rff) 4 6 -4 6 18 -10 8 35 -13 10 58 -15 12 87 -17 14 122 -19 16 162 -20 18 208 -21 20 260 -22 In Table 2-1, RFF was calculated from Eqn 1 for a typical LFAA VLA. The third column in Table 2-1 demonstrates the difference between the element source level and the on-axis receive level calculated by using the subaperture method: RL[RFF(NS)] = SLE + 20Log(NS) - 20Log(RFF) [Column 3 of Table 2-1]
  • Effective SL in the Near field & Fairfield Regions Near field Region •Diffuse unfocused beam Farfield Region •Receive Level near HLA = SLE •Focused beam •Cannot Measure Effective SL of •RL=SLE+20Log(NE)-TL the array •Can Measure ‘Effective SL’ of •RL not equal to Far-Field SL-TL the array •Velocity component 3 dimensional •RL equals SL-TL & computed by dP/dx, dP/dy, dP/dz RFF Horizontal Line Array (HLA) Source, Example shows 4 elements Range
  • Transmitted Near Field Pressure Sound Levels from a lateral Distance in meters Low Frequency Multi-Element HLA 150 100 50 Array Main Response Axis Horizontal Axis 0 0 100 200 300 Vertical Range in meters Receive Level relative to the SL of an individual element, SLE 0 -20 -40 -60 -80
  • Fig 2-2: Comparing Actual Coherent Array Levels on Axis with the Far Field Approximation & a SubAperture Approximation (Element SL=0dB, 20 Elements, Narrowband Signal) 30 20*log(|Coherent sum|) 20 20log(N)-20Log(R) 10 Sub Aperture Approx Receive Level in dB 0 -10 -20 -30 -40 -50 -60 1.0 10.0 100.0 1000.0 Range in meters
  • Particle velocity considerations (single element seismic example) Particle velocity in the radial Particle velocity normal to the radial direction for the 50Hz source at 7m direction for the 50Hz source at 7m depth, log scale in cm/sec, i.e. @ depth, log scale in cm/sec, i.e. @ color scale = -1, uR = 1x10-1 cm/sec color scale = -1, Ut = 1x10-1 cm/sec Based on same analytical technique used for line array with MATLAB Graphics Based on same analytical technique used for line array with MATLAB Graphics
  • Examples of Bioacoustic Research (Past & Present) –Bowhead Whales in the Arctic (1980’s) –SOCAL SRP Tagged Fin Whale –Stellwagen Bank NOPP (Today)
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