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Mechanical Engineering
UNIVERSITY OF WASHINGTON
COLLEGE of ENGINEERING A Community of Innovators
Prof. Peter Dahl
Acoustics Research in Mechanical Engineering and at the Applied Physics
LaboratoryResearch Areas: Underwater acoustics
originating from the sedimentoriginating from the water
Underwater Noise from Marine Pile Driving(Co-PIs: Reinhall and Dahl)
Reinhall, P.G., and P. H. Dahl, Underwater Mach wave radiation from impact pile driving: Theory and observation, J. Acoust. Soc. Am., 130(3) 1209-1216, Sep. 2011
Finite element modeling shows wheresound originates: first in the water, then (~ +10 ms) from the sediment
Field measurements (right) from Vashonisland confirm the modeling
Underwater noise frompile driving can harmmarine life
Reducing this noisefirst requires that we understand it
Transmission Loss Studies in Puget Sound
(PI: Dahl)
Transmission Loss (TL) is a measure of how sound intensity is reduced with increasing distance from its source
TL is used to predict environmentalimpacts of underwater sound fromnoise sources such as pile driving
Whidbey Island
Sound Source
CamanoIsland
TL is displayed (right) using Geographical Information System (GIS) or (below) showing more detail
Vector Acoustics(PI: Dahl)
Vector acoustics provides a means to exploreunderwater sound in new ways by exploitingacoustic particle velocity
Dall’Osto D.R., P. H. Dahl, and J. W. Choi, Properties of the acoustic intensity vector field in a shallow water waveguide, J. Acoust. Soc. Am., 131 (3) 2023-2035 Mar. 2012
Simulated acoustic field versus depth and range at snapshots in time. Sound source (80 m) is deployed from ship shown at left. Acoustic particle motion and vector intensity can be measured with accelerometers combined with ordinary pressure sensors (a combined sensor)
Particle motion can show the direction of sound--but interferencewhen two acoustic paths intersect causes elliptical motion (time ~117 ms)
time from start of pulse (some segments slowed down) 1480 1510 1540
sound speed (m/s)
seabed
Acoustic particle motion(amplified for display)from sensors atdepths 20 and 50 m