Attenuation of noise from impact pile driving in water using an acoustic shield

Jan. 31, 2015

AUTHORS

Per G. Reinhall, Peter H. Dahl and John T. Dardis

ABSTRACT

Offshore impact pile driving produces extremely high sound levels in water. Peak acoustic pressures from the pile driving operation of ~103 Pa at a range of 3000 m, ~104 Pa at a range of 60 m, and ~105 Pa at a range of 10 m have been measured. Pressures of these magnitudes can have negative effects on both fish and marine mammals. Previously, it was shown that the primary source of sound originates from radial expansion of the pile as a compression wavepropagates down the pile after each strike. As the compression wave travels it produces an acoustic field in the shape of an axisymmetric cone, or Mach cone. The field associated with this cone clearly dominates the peak pressures. In this paper, we present an evaluation of the effectiveness of attenuating pile driving noise using an acoustic shield. In order to fully evaluate the acoustic shield, we provide results from finite element modeling and simple plane waveanalysis of impact pile driving events with and without a noise shield. This effort is supported by the findings from a full-scale pile driving experiment designed to evaluate the effectiveness of thenoise shield. Finally, we will discuss methods for improving the effectiveness of the acoustic shield.

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http://scitation.aip.org/content/asa/journal/jasa/135/4/10.1121/1.4877896

"By reducing underwater noise from pile driving by 20 dB, implementation of MCT’s technology could potentially reduce the Zone of Influence and required marine mammal monitoring, expedite consultation processes with the Services, and minimize construction delays due to the proximity of marine mammals."
Cameron Fisher, Biological Lead, 48 North Solutions, Inc.

Hear the difference

Recorded from hydrophone deployed at 10m during subscale testing of 8" steel piles in Seattle, Washington in 2013.

You are hearing 4 strikes of a standard pile followed by 4 strikes of a Reinhall Pile™. Notice the difference.