Characterization of Underwater Sounds Produced by Dredges

Characterization of underwater sounds produced by hydraulic and mechanical dredging operations

“…The larger size class hopper dredges were similar to a container ship traveling at a modest speed. Overall, bucket dredging operations monitored by Miles et al (Miles et al,1986;Miles et al,1987) and Clarke et al (2002) were relatively quiet with SLs 28-34 dB lower than shipping and ferry vessels monitored in the current study.…”

“…Relatively muted sounds are produced by the draghead while in contact with the sediment bed at least when the dredge is working in fine maintenance sediments (grain size ¼ 3.9-62.5 lm). Hopper dredge sounds are relatively continuous rather than punctuated (Clarke et al, 2002). In contrast to the highly mobile TSHDs, CSDs [ Fig.…”

“…The duration of production "cuts" depends on a number of factors, including depth of insertion of the cutterhead, type of sediment being excavated, and width of the navigation channel. CSD sounds are therefore largely continuous (Clarke et al, 2002). For hydraulic dredging operations, the major processes contributing to underwater sounds include: (1) Dredged material collection sounds originating from the rotating cutterhead in contact with the bed and intake of the sediment-water slurry, (2) sounds generated by pumps and impellers driving the suction of material through the pipes, (3) transport sounds involving the movement of sediment through the pipes, and (4) ship and machinery sounds, including those associated with the lowering and lifting of spuds and moving of anchors by dredge tenders.…”

A Summary of Existing and Future Potential Treatments for Reducing Underwater Sounds from Oil and Gas Industry Activities

“…The available literature provides little to no information on the relative amplitudes of noises that come from the vessel machinery relative to the dredging head for non-bucket dredging operations. Reference [48] does state (referring to a hopper dredge), "sounds of the draghead scraping across the sandy substrate could be discerned from propeller noise" only for measurements where the vessel was close (40 meters) to the recording hydrophone. This reference also states (referring to a cutterhead dredge), "even at very short distances from the cutterhead, rotation of the assembly produced very muted sounds," and goes on to say, "sounds... could not be partitioned into discrete components attributable to separate sound sources."…”

Characterization of Underwater Sounds Produced by Trailing Suction Hopper Dredges During Sand Mining and Pump-out Operations

“…Few data exist that adequately characterize sounds emitted by dredges that would support objective decisions balancing the need to dredge against relative risk to an aquatic resource. Studies by Greene (1985Greene ( , 1987; Miles et al (1986Miles et al ( , 1987; Dickerson et al (2001); Clarke et al (2002); Department for Environment, Food, and Rural Affairs (DEFRA) (2003); Parvin et al (2008); and more recently, de Jong et al (2010); Robinson et al (2011);andReine et el. (2012a, 2012b, in preparation) are among the very few relevant references that exist.…”