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Peter Dahl

Senior Principal Engineer

Professor, Mechanical Engineering

Email

dahl97@uw.edu

Phone

206-543-2667

Research Interests

Underwater Acoustics, Acoustic Remote Sensing

Biosketch

Dr. Dahl is a Senior Principal Engineer in the Acoustics Department and a Professor in the University of Washington's Department of Mechanical Engineering. Professor Dahl's research is in areas of acoustics with primary focus on underwater sound. Examples of his research include underwater acoustic remote sensing, the acoustics of underwater explosions, acoustic scattering and reflection from the sea surface and sea bed, vector acoustics, underwater ambient noise and methods to reduce underwater industrial noise.

He has conducted several ocean-going experiments involving underwater acoustics, including the Asian Seas International Acoustics Experiment (ASIAEX), sponsored by the U.S. Office of Naval Research, in the East China Sea involving the U.S., China and Korea and for which he was U.S. chief scientist.

Professor Dahl is a Fellow of the Acoustical Society of America, has served as the chair of its technical committee on underwater acoustics (2002–2005), on its Executive Council (2008–2011), and has recently completed service as Vice President of the Acoustical Society of America.

Department Affiliation

Acoustics

Education

B.S., University of Washington - Seattle, 1976

M.S. Ocean and Fishery Sciences, University of Washington - Seattle, 1982

Ph.D. Ocean Engineering, MIT, 1989

Publications

2000-present and while at APL-UW

Characterizing deep sediments of the Eastern US Continental Shelf from the discrete Doppler spread of moving low-frequency tonal sources

Dall'Osto, D.R., and P.H. Dahl, "Characterizing deep sediments of the Eastern US Continental Shelf from the discrete Doppler spread of moving low-frequency tonal sources," J. Acoust. Soc. Am., 158, 2703-2713, doi:10.1121/10.0039512, 2025.

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8 Oct 2025

The Doppler shift of tonal sound waves generated by a moving source provides a means to identify source energy radiating from different angles, relative to its motion. In shallow water, the shift imparted on a laterally moving source depends on the elevation angle, and a single generating tone may be received as multiple frequencies, each corresponding to sound propagating at an angle of the discrete normal modes. Using a geoacoustic model consistent with those emerging from studies conducted at the New England Mud Patch (NEMP), predictions of mode angles correlate to the observed mode angles at 57 Hz. For lower frequencies, this study examines harmonic tones from a container ship traversing the eastern U.S. Continental Shelf from west to east over a 150-km range. Observations of multiple non-resonant modes at the lowest harmonics (~5 Hz) imply an increase in sound speed over an ~1.5-km-thick sediment layer, terminating in a higher-speed rock basement. These data show a shift in mode angle commencing ~75 km east of the NEMP, suggesting a significant change in sediment type and thickness.

Observations and modeling of range-dependent propagation in low-frequency tones emitted by a container ship

Dahl, P.H., and Dall'Osto, D.R., "Observations and modeling of range-dependent propagation in low-frequency tones emitted by a container ship," J. Acoust. Soc. Am., 158, 2752-2762, doi:10.1121/10.0037228, 2025.

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8 Oct 2025

Observations of tonal emissions over frequencies similar to 9.5–36 Hz from a merchant vessel along a 31.5-km track are used to study seabed properties on the New England Mud Patch, an area distinguished by a low sound speed mud layer of thickness similar to 10 m commencing at the water–sediment interface. The data are forward-modeled using adiabatic normal modes based on a range-varying geoacoustic model for the upper sediments, reproducing key effects such as changing mode interference patterns. For the deep sediments, a proposed linear sound speed gradient governs an increasing compressional speed with depth. Bayesian inversion yields frequency-dependent estimates of the compressional wave attenuation within the deep sediments using data from the lower frequencies for which it is possible to disambiguate the effect of attenuation from the upper mud layer. At similar to 16 Hz, the highest frequency meeting this condition, this estimate is 0.17 ± 0.03 dB/λ, and these inversion results are used to infer corresponding values for the higher frequencies. A compressional wave attenuation of 0.05 dB/λ in the mud layer is applied across all frequencies. Elastic effects are included in the geoacoustic candidate models used in the inversion; removing them increases compressional wave attenuation 10%–40% depending on frequency.

Estimation of the spatial variability of the New England Mud Patch geoacoustic properties using a distributed array of hydrophones and deep learning

Vardi, A., P.H. Dahl, D. Dall'Osto, D. Knobles, P. Wilson, J. Leonard, and J. Bonnel, "Estimation of the spatial variability of the New England Mud Patch geoacoustic properties using a distributed array of hydrophones and deep learning," J. Acoust. Soc., Am., 156, 4229-4241, doi:10.1121/10.0034707, 2024.

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24 Dec 2024

This article presents a spatial environmental inversion scheme using broadband impulse signals with deep learning (DL) to model a single spatially-varying sediment layer over a fixed basement. The method is applied to data from the Seabed Characterization Experiment 2022 (SBCEX22) in the New England Mud-Patch (NEMP). Signal Underwater Sound (SUS) explosive charges generated impulsive signals recorded by a distributed array of bottom-moored hydrophones. The inversion scheme is first validated on a range-dependent synthetic test set simulating SBCEX22 conditions, then applied to experimental data to predict the lateral spatial structure of sediment sound speed and its ratio with the interfacial water sound speed. Traditional geoacoustic inversion requires significant computational resources. Here, a neural network enables rapid single-signal inversion, allowing the processing of 1836 signals along 722 tracks. The method is applied to both synthetic and experimental data. Results from experimental data suggest an increase in both absolute compressional sound speed and sound speed ratio from southwest to northeast in the NEMP, consistent with published coring surveys and geoacoustic inversion results. This approach demonstrates the potential of DL for efficient spatial geoacoustic inversion in shallow water environments.

More Publications

Inventions

Pile with Sound Abatement

Patent Number: 9,617,702

Peter Dahl, John Dardis II, Per Reinhall

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Patent

11 Apr 2017

A noise-attenuating pile comprising a pile driving shoe, an outer tube that engages the pile driving shoe, and an inner member that extends through the outer tube and engages the pile driving shoe, wherein the pile is configured to be installed in sediment or other suitable material by driving the inner member with a pile driver, without directly impacting the outer tube, such that the radial outer tube is substantially insulated from the radial expansion waves generated by the pile driver impacting the inner member. In some piles, one of the inner member and the outer tube are removable after installation. In some piles, a seal is provided in a lower end of the channel defined between the inner member and the outer tube, which may be biodegradable, or may be an inflatable bladder, for example.

Pile to Minimize Noise Transmission and Method of Pile Driving

Patent Number: 8,622,658

Per G. Reinhall, Peter Dahl

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Patent

7 Jan 2014

A pile and method for driving a pile includes a pile having a structural outer tube, and an inner member disposed generally concentrically with the outer tube. The outer tube and inner member are fixed to a driving shoe. The pile is constructed and driven such that the pile driver impacts only the inner member. The impact loads are transmitted to the driving shoe to drive the pile into the sediment, such that the outer tube is thereby pulled into the sediment. In a particular embodiment the outer tube is formed of steel, and the inner member also comprises a steel tube. In an alternative embodiment one or both of the inner member and the outer tube are formed of an alternative material, for example, concrete. In an embodiment, the outer tube has a recess that captures a flange on the inner member. In an embodiment the outer tube is attached to the inner member with an elastic spring.

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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