1. 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 Laboratory Research Areas: Underwater acoustics

2. originating from the sediment originating 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 where sound originates: first in the water, then (~ +10 ms) from the sediment Field measurements (right) from Vashon island confirm the modeling Underwater noise from pile driving can harm marine life Reducing this noise first requires that we understand it

3. 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 environmental impacts of underwater sound from noise sources such as pile driving Whidbey Island Sound Source Camano Island TL is displayed (right) using Geographical Information System (GIS) or (below) showing more detail

4. Vector Acoustics (PI: Dahl) Vector acoustics provides a means to explore underwater sound in new ways by exploiting acoustic 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 interference when two acoustic paths intersect causes elliptical motion (time ~117 ms) time from start of pulse (some segments slowed down) 14801510 1540 sound speed (m/s) seabed Acoustic particle motion (amplified for display) from sensors at depths 20 and 50 m