Underwater noise and transmission loss from vibratory pile driving

• Published in: The Journal of the Acoustical Society of America 2014-10, Vol.136 (4_Supplement), p.2206-2207
• Main Authors: Dahl, Peter H., Farrell, Dara M.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4900004

High levels of underwater sound can be produced in vibratory pile driving that can carry regulatory implications. In this presentation, observations of underwater noise from vibratory pile driving made with a vertical line array placed at range 17 m from the source (water depth 7.5 m) are discussed, along with simultaneous measurements made at ranges of order 100 m. It is shown that the dominant spectral features are related to the frequency of the vibratory pile driving hammer (typically 15–35 Hz), producing spectral lines at intervals of this frequency. Homomorphic analysis removes these lines to reveal the underlying variance spectrum. The mean square pressure versus depth is subsequently studied in octave bands in view of the aforementioned spectral line property, with depth variation well modeled by an incoherent sum of sources distributed over the water column. Adiabatic mode theory is used to model the range dependent local bathymetry, including the effect of elastic seabed, and comparisons are made with simultaneous measurements of the mean-square acoustic pressure at ranges 200 and 400 m. This approach makes clear headway into the problem of predicting transmission loss versus range for this method of pile driving.