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STUDY TITLE: A Parametric Analysis and Sensitivity Study of the Acoustic Propagation for 

Renewable Energy Sources and Projects

REPORT TITLE: A Parametric Analysis and Sensitivity Study of the Acoustic Propagation for 

Renewable Energy Sources

CONTRACT NUMBER(S): M17PD00003

SPONSORING OCS REGION: Office of Renewable Energy Programs

APPLICABLE PLANNING AREA(S): U.S. North to Mid-Atlantic Coast Planning area out to 60 m 

water depth. 

FISCAL YEAR(S) OF PROJECT FUNDING: 2017-2020

COMPLETION DATE OF REPORT: 9 February 2020 

COST(S): (BY FISCAL YEAR); CUMULATIVE PROJECT COST: FY17: $72,667.59; 

FY19: $58,105.83; FY20: $29,602.06

PROJECT MANAGER(S): Michele B. Halvorsen, Ph.D 

AFFILIATION (OF PROJECT MANAGER): CSA Ocean Sciences Inc.

ADDRESS: 8502 SW Kansas Avenue, Stuart, Florida, 34997

PRINCIPAL INVESTIGATOR(S): Kevin Heaney1 Ph.D., Michael A Ainslie2 Ph.D., and Michele 

B. Halvorsen, Ph.D.;

KEY WORDS: Pile driving, acoustic radiation; acoustic propagation; finite element, parabolic 

equation; damped cylindrical spreading; marine mammal; fish; sea turtle; impact volume; 

sensitivity; grain size; season, U.S. East Coast. 

BACKGROUND: Modern acoustic propagation models make assumptions that are partially 

inapplicable to pile driving. The main assumption that does not apply is that a far field exists for 

pile driving. For a far field to exist, there must be a region far enough from a source in which the 

sound spreads spherically, thereby appearing to radiate from a single point. The non-existence 

of a far field for pile driving means that the concept of source level is undefined, which in turn 

means the concept of propagation loss (PL) is undefined, which makes widely used models 

such as the range-dependent acoustic model (RAM) inapplicable unless the model is coupled to 

a known starting field close to the pile. Work in the early 2010s treated the pile as a compound 

source with a vertical array of phase-delayed monopoles. Later work, in the mid-2010s, applied

a finite element (FE) model of the hammer and pile to generate the starter field.

OBJECTIVES: The purpose of this study was to perform a technical analysis of acoustic 

propagation modeling of pile driving for wind turbine installations on the U.S. Atlantic continental 

shelf to 1) recommend a consistent underwater acoustic modeling approach across renewable 

energy projects, including recommendations for appropriate models, databases, and 

methodologies that address pile driving; 2) provide a baseline range of expected modeling 

1 Applied Ocean Sciences. LLC., 11006 Clara Barton Dr. Fairfax Station, VA 22039 

2 Jasco Applied Sciences (Deutschland) GmbH, Mergenthaler Allee 15-21, 65760 Eschborn, Hesse, Germany.
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results, including impact volumes around typical sources; 3) identify a baseline of variability for 

acoustic modeling results based on ranges of critical environmental input parameters; 4) 

perform a sensitivity study of critical environmental parameter influences; and 5) validate and 

apply the damped cylindrical spreading method, including its implementation in Excel.

DESCRIPTION: The sound field radiated by a pile was quantified using a specialized FE model 

of the hammer, anvil, pile, and surrounding media. The FE model field was propagated to 

approximately 60 km range using a parabolic equation (PE) acoustic propagation model. 

Ultimately, the acoustic field was characterized in terms of the root-mean-square sound 

pressure level, peak sound pressure level, and single strike sound exposure level.

As proxies for water depth and oceanography, two sites off the U.S. Atlantic Coast, near Rhode 

Island (RIsland) and Virginia Beach (VAbeach), were chosen for modeling. The environmental 

variable with the greatest impact on acoustic propagation was the site itself. Besides water depth, 

the sites also differed by distance to shore and had unique bathymetries. RIsland was closer to 

land and deeper than VAbeach, leading to differences of 40 dB at ranges beyond 20 km from the 

source. Lastly, impact volume was determined by calculating the acoustic metrics as a function 

of distance away from the pile and comparing the metric values with acoustic impact thresholds. 

SIGNIFICANT CONCLUSIONS: A notable finding of this study was that close to the pile (up to 

about 5 km) the sound field decays according to a cylindrical spreading power law combined 

with exponential decay. In this region the transmission loss (TL) decreases with increasing 

water depth and sediment grain size (i.e., the higher the TL, the lower the impact volume). 

Further away the field depends also on bathymetry and season, with lowest TL (i.e., largest 

impact volume) occurring for downslope conditions (i.e., water depth increasing away from the 

pile) and in the winter. Conversely, highest TL (i.e., lowest impact volume) occurred for upslope 

conditions (water depth decreasing away from the pile) and in the summer. 

Changes in sediment type exerted the next largest influence on impact volume. Hard sediments 

reflect sound more than soft sediments, leading to larger impact volumes over harder 

sediments. Season had a smaller effect, with better propagation in winter than in summer, which 

led to higher received levels at all ranges and; therefore, larger impact volumes in winter. 

Summer impact volumes were smaller because warm surface waters lead to increased 

refraction towards the seafloor and thus more absorption of sound into the seafloor.

SIGNIFICANT RESULTS: This study developed a methodology for accurately computing the 

received acoustic field as a function of range, bearing and depth from an impact pile in a rangedependent environment. The combined FE/PE model was required to handle the non-point 

source nature of the pile and the range-dependent bathymetry at ranges beyond 5 km. A 

significant result is that the model was able to match previous numerical studies (from the 2014 

COMPILE workshop) as well as measurements at ranges from 730 m to 65 km for all 

frequencies from a single pile installment (Gemini) off the coast of the Netherlands. 

Developed an acoustic prediction tool in excel that is based on damped cylindrical spreading 

method. The tool provides a more accurate and robust acoustic prediction for pile driving in the 

ocean based on in-field data measurements (from the EU) that were tested against the new 

acoustic model.

STUDY PRODUCT(S): 

1. BOEM Report: Heaney KD, MA Ainslie, MB Halvorsen, KD Seger, RAJ Müller, MJJ 

Nijhof, T Lippert. 2020.A Parametric Analysis and Sensitivity Study of the Acoustic 

Propagation for Renewable EnergySources. Sterling (VA): U.S. Department of the 
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Interior, Bureau of Ocean Energy Management.Prepared by CSA Ocean Sciences Inc. 

OCS Study BOEM 2020-011. 165 p.

2. A user-spreadsheet for calculating impact ranges from pile driving (DCSiE, pronounced 

“Dixie”).