A deep ocean acoustic noise floor, 1–800 Hz

View/ Open
Date
2018-02-26Author
Berger, Jonathan
Concept link
Bidlot, Jean-Raymond
Concept link
Dzieciuch, Matthew A.
Concept link
Farrell, W. E.
Concept link
Worcester, Peter F.
Concept link
Stephen, Ralph A.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/10515As published
https://doi.org/10.1121/1.5025042DOI
10.1121/1.5025042Abstract
The ocean acoustic noise floor (observed when the overhead wind is low, ships are distant, and marine life silent) has been measured on an array extending up 987 m from 5048 m depth in the eastern North Pacific, in what is one of only a few recent measurements of the vertical noise distribution near the seafloor in the deep ocean. The floor is roughly independent of depth for 1–6 Hz, and the slope (∼ f−7) is consistent with Longuet-Higgins radiation from oppositely-directed surface waves. Above 6 Hz, the acoustic floor increases with frequency due to distant shipping before falling as ∼ f−2 from 40 to 800 Hz. The noise floor just above the seafloor is only about 5 dB greater than during the 1975 CHURCH OPAL experiment (50–200 Hz), even though these measurements are not subject to the same bathymetric blockage. The floor increases up the array by roughly 15 dB for 40–500 Hz. Immediately above the seafloor, the acoustic energy is concentrated in a narrow, horizontal beam that narrows as f−1 and has a beam width at 75 Hz that is less than the array resolution. The power in the beam falls more steeply with frequency than the omnidirectional spectrum.
Description
Author Posting. © Acoustical Society of America, 2018. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 143 (2018): 1223, doi:10.1121/1.5025042.
Collections
Suggested Citation
Journal of the Acoustical Society of America 143 (2018): 1223Related items
Showing items related by title, author, creator and subject.
-
Deep seafloor arrivals in long range ocean acoustic propagation
Stephen, Ralph A.; Bolmer, S. Thompson; Udovydchenkov, Ilya A.; Worcester, Peter F.; Dzieciuch, Matthew A.; Andrew, Rex K.; Mercer, James A.; Colosi, John A.; Howe, Bruce M. (Acoustical Society of America, 2013-10)Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean ... -
Sonar-induced pressure fields in a post-mortem common dolphin
Foote, Kenneth G.; Hastings, Mardi C.; Ketten, Darlene R.; Lin, Ying-Tsong; Reidenberg, Joy S.; Rye, Kent (Acoustical Society of America, 2012-02)Potential physical effects of sonar transmissions on marine mammals were investigated by measuring pressure fields induced in a 119-kg, 211-cm-long, young adult male common dolphin (Delphinus delphis) cadaver. The specimen ... -
Observationally constrained modeling of sound in curved ocean internal waves: Examination of deep ducting and surface ducting at short range
Duda, Timothy F.; Lin, Ying-Tsong; Reeder, D. Benjamin (Acoustical Society of America, 2011-09)A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional ...