Oceans of noise - Whale and Dolphin Conservation Society

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Figure 3.4. Sound transmission pathways and sources of noise associated with a drill ship or an
FPSO (floating production storage and offloading facility). (1) Cavitation associated with the
propeller, (2) Cavitation associated with bow and stern thrusters, (3) Exhaust ports, (4) Hull
vibration associated with machinery noise, (5) Vibration through drill string casing or risers, (6)
Vibration of the drill bit. Red - Gas turbines (Machinery noise), Light blue - Compressors
(Machinery noise), Yellow - Separators (Machinery noise), Dark blue - Water injection pumps
(Machinery noise), Green - Propulsion units – thrusters (Machinery noise + propeller noise).
It is difficult to predict which species will be most vulnerable to man-made noise because of the
wide range of individual and population sensitivities as well as differences in wariness or
motivation. Currently, it may only be possible to make generalisations about the vulnerability of
species groups based on behavioural observations of responses to man made sounds, habits and
what is known about a species’ auditory sensitivity or vocal range.
When evaluating likely impacts, consideration should also be given to differences in local
conditions that may affect sound propagation, e.g. depth, bottom type, size and type of source. As
can be seen in the table below, a majority of man-made sounds have significant amounts of
energy at low frequencies, thereby leading to potential disturbance, damage or interference to the
mysticete whales. There is evidence of low frequency hearing in sperm whales (Ketten, 1992;
Ketten, 1997) and this species appears to be extremely sensitive to disturbance from a variety of
sound sources. Deep diving odontocetes may also be at risk as their behaviour puts them in the
deep sound channel or SOund Fixing And Ranging (SOFAR) channel, along which sound is
believed to travel efficiently for distances of hundreds to thousands of kilometres. Noise from
seismic sources tends to be focussed downwards, exposing any submerged or deep diving
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Drill bit
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