Pile driving in water produces high sound levels in underwater environments. The associated pressures are known to produce deleterious effects on both fish and marine mammals. We present an evaluation of the effectiveness of surrounding the pile with a double walled sound shield to decrease impact pile driving noise. Four 32 m long, 76 cm diameter piles were driven 14 m into the sediment with a vibratory hammer. A double walled sound shield was then installed around the pile, and the pile was impact driven another 3 m while sound measurements were obtained. The last 0.3 m was driven with the sound shield removed, and data were collected for the untreated pile. The sound field obtained by finite element analysis is shown to agree well with measure data. The effectiveness of the sound shield is found to be limited by the fact that an upward moving Mach wave is produced in the sediment after the first reflection of the deformation wave against the bottom end of the pile. The sound reduction obtained through the use of the sound shield, as measured 10 meters away from the pile, is shown to be approximately 12dB dB re 1 µPa.

As communities seek to expand and upgrade marine and transportation infrastructure, underwater noise from pile driving associated with marine construction is a significant environmental regulatory challenge. This work explores results of different transmission loss models for a site in Puget Sound and the effect of improved understanding of modeling on the extents of zones of influence. It has been observed that most of the energy associated with impact pile driving is less than about 1000 Hz. Here, analysis of the spectral content of pile driving noise is undertaken to ascertain the optimal surrogate frequency to model the broadband nature of the noise. Included is a comparison of a normal mode model, which is motivated by work presented by Reinhall and Dahl [JASA 130, 1209 (2011)], with other methods. A GIS (Geographic Information System) tool, ArcMap, is used to map the sound level over the bathymetry, which has proved to be a useful way of visualizing the impact of the noise.

Pile driving in water produces extremely high sound pressure levels in the surrounding underwater environment of order 10 kPa at ranges of order 10 m from the pile that can result in deleterious effects on both fish and marine mammals. In Reinhall and Dahl [J. Acoust. Soc. Am. 130, 1209-1216, Sep. 2011] it is shown that the dominant underwater noise from impact driving is from the Mach wave associated with the radial expansion of the pile that propagates down the pile at speeds in excess of Mach 3 with respect to the underwater sound speed. In this talk we focus on observations of the Mach wave effect made with a 5.6 m-length vertical line array, at ranges 8-15 m in waters of depth ~12.5 m. The key observation is the dominant vertical arrival angle associated with the Mach wave, ~17 deg., but other observations include: its frequency dependence, the ratio of purely waterborne energy compared with that which emerges from the sediment, and results of a mode filtering operation which also points to the same dominant angle. Finally, these observations suggest a model for transmission loss which will also be discussed.

The underwater noise from impact pile driving is studied using a finite element model for the sound generation and parabolic equation model for propagation. Results are compared with measurements using a vertical line array deployed at a marine construction site in Puget Sound. It is shown that the dominant underwater noise from impact driving is from the Mach wave associated with the radial expansion of the pile that propagates down the pile after impact at supersonic speed. The predictions of vertical arrival angle associated with the Mach cone, peak pressure level as function of depth, and dominant features of the pressure timeseries compare well with corresponding field observations.

Pile driving in water produces extremely high sound levels in the surrounding under water environment. Sound levels as high as 220 dB re 1 micro Pa are not uncommon 10 m away from a steel pile as it is driven into the sediment with an impact hammer. The primary source of underwater sound originating from pile driving is associated with compression of the pile. The pile is struck and the Poisson effect produces a radial displacement motion in the pile that will propagate downward at a computed speed comparable to but less than the longitudinal wave speed in steel. It is shown, using both finite element analysis and modeling based on the parabolic wave equation, that this radial motion of the pile is responsible for the ensuing high underwater sound pressures. It is also shown that the radial motion of the pile is transmitted into the water, either directly from the pile or indirectly via the bottom sediment that is in contact with the pile. A dominant feature of the resulting sound field is an axisymmetric Mach cone with apex traveling along with the pile deformation wave front.

Industrial pile driving is a source of high-level underwater noise and new understanding of its effects on the behavior and health of marine mammals and fish has motivated numerous regulations intended to limit these effects. Of primary importance is to identify a suitable transmission loss model to predict where, given a certain source level, the noise produced by the pile driving reaches regulatory thresholds. In November 2009, data were collected from a marine construction site in the Puget Sound. Measurements at two ranges (8 and 12 m) from the pile being driven were taken using a nine hydrophone vertical line array (VLA). Concurrently, at a range of approximately 120 m, there was also a single hydrophone at a depth of 5 m (sensitive to frequencies greater than 10 kHz). By comparing the levels at the VLA to the more distant hydrophone across a number of pile strikes (each forming a identifiable short- and far-range pair), the transmission loss can be estimated. These results are in turn modeled using an approach based on the parabolic wave equation.

Pile driving in water produces extremely high sound levels in both surrounding air and underwater environments. In a companion work [Reinhall and Dahl] it is shown using finite element simulation that for underwater case the primary sound signal originates from a compression wave traveling down the pile at a speed in excess of Mach 3. In this work, we present measurements pile driving impact noise made from a marine construction site in Puget Sound using a vertical line array (VLA) positioned at ranges 815 m from full-scale impact pile driving. The measurements are modeled using the parabolic wave equation approach for which synthetic time series are generated (bandwidth 50-2050 Hz). The simulation is achieved by way of a phased array of point sources, representing one source traveling down the pile at supersonic speed. Pile end reflections are included and the process is repeated with both an up- and down-traveling time-delayed sources. With the field computed in this manner, excellent agreement is achieved between model and observations of peak pressure level, and the compression wave speed is also confirmed by way of arrival angle estimation using the VLA. Implications on transmission loss are also discussed.

Pile driving with an impact hammer is inherently a transient process and can produce very high sound levels. It is shown that the underwater noise during pile driving is due to a radial expansion of the pile that propagates along the pile after impact. This structural wave produces a wave front cone in the water, and a downward moving wave that continues into the sediment. An upward moving wave front is produced in the sediment after the first reflection of the structural wave, which is subsequently transmitted into the water. This process is repeated to produce an acoustic field that consists of wave fronts with alternating positive and negative angles. Good agreement in the estimate of the angles was obtained between a finite element wave propagation model and measurements taken during a full scale pile driving study.

Acoustic radiation in the water surrounding a ferry terminal pile driving project has been characterized based on 1/3-octave band filtering. The pressure field at approximately 10 meters is shown to be depth dependent based on data captured using a vertical line array. Decibel measurements of underwater sound are often expressed in reference to several non-interchangeable units, a summary of the differences of these references is presented.