Title: Ambient hydro-acoustic noise in the ocean
1Ambient hydro-acoustic noise in the ocean
impact of merchant ships, and developments at IMO
- Martin Renilson, (martin.renilson_at_hct.ac.ae)
- Higher Colleges of Technology
- Russell Leaper,
- International Fund for Animal Welfare, and
- Oliver Boisseau,
- Marine Conservation Research International
- Date of document 30 August 2014
2Contents
- The problem of underwater noise pollution from
shipping - International recognition of the need to address
the problem - Action by IMO
- Key aspects of the shipping noise problem
- Practical technologies for reducing noise on
merchant ships - Research needs and recommendations
- Concluding remarks
3The problem of underwater noise pollution from
shipping
- Documented increase in ambient noise across
oceans in recent decades of 20dB - Affects all marine life with sensitive hearing
- many fish species, and
- marine mammals
- For many species, sound is most important sense
- Underwater noise pollution causes
- displacement
- stress
- masks sounds used for communication and finding
food
4- The main frequencies from shipping noise overlap
whales, dolphins, fish, seals and sea lions, but
particularly the large baleen whales such as fin,
blue, right and humpback (Figure taken from IMO
MEPC 58/19)
5International recognition of the need to address
the problem
- First raised in the 1970s, but serious attention
only in recent years - The International Workshop on Shipping Noise and
Marine Mammals in 2008 target of a reduction in
shipping noise levels in 10-300Hz range - 3dB in 10 years and
- 10dB in 30 years
- The European Union Indicator for Good Environment
Status will include low frequency underwater noise
6Action by IMO
- In 2008 IMO MEPC added Noise from commercial
shipping and its adverse impact on marine life
as a high priority item - The IMO correspondence group was tasked with
developing non-mandatory guidelines - ship-quieting technologies
- potential navigation and operational practices
7Key aspects of the shipping noise problem
- Little attention to underwater radiated noise in
ship design and construction to date - Noise output may vary substantially due to
otherwise relatively minor changes - ballast
- trim
- propeller damage
- speed
- controllable pitch settings
8Key aspects of the shipping noise problem
- Quieting relatively few of the loudest ships is a
potential way to efficiently reduce the overall
contribution of shipping noise to the global
ocean noise budget - noisiest 10 of vessels cause the majority of the
noise pollution - Mandatory Energy Efficiency Design Index (EEDI)
introduced by IMO presents an opportunity to
address noise reduction alongside increased
efficiency
9Practical technologies for reducing noise on
merchant ships
- Propeller cavitation is main culprit for noisiest
ships
10Practical technologies for reducing noise on
merchant ships
- Propeller cavitation is main culprit for noisiest
ships - Specialist warship propellers avoid cavitation,
so are quieter, but reduce efficiency not
acceptable for merchant ships - Cavitation cannot be avoided altogether for
merchant ships but can be reduced for the
noisiest ones
11Practical technologies for reducing noise on
merchant ships
- Strategies for noisiest merchant ships
- Propeller design
- Wake flow into propeller
- Changes to operating procedure
12Practical technologies for reducing noise on
merchant ships
- Propeller design
- Strategies
- High skew propellers
High skew, high BAR
No skew
High skew
13Practical technologies for reducing noise on
merchant ships
- Propeller design
- Strategies
- High skew propellers
- Contracted loaded tip
- propeller
14Practical technologies for reducing noise on
merchant ships
- Propeller design
- Strategies
- High skew propellers
- Contracted loaded tip propeller
- Kappel propeller
15Practical technologies for reducing noise on
merchant ships
- Propeller design
- Strategies
- High skew propellers
- Contracted loaded tip propeller
- Kappel propeller
- Other specialist propeller types
- Redesign propeller for actual operating condition
once known special care for CPP - Propeller hub caps (various concepts)
16Practical technologies for reducing noise on
merchant ships
17Practical technologies for reducing noise on
merchant ships
www.largestships.com
18Practical technologies for reducing noise on
merchant ships
- Wake flow into propeller
- Strategies
- Wake inflow devices
19Practical technologies for reducing noise on
merchant ships
- Wake flow into propeller
- Strategies
- Wake inflow devices
- Propeller/Rudder interaction
Rolls-Royce
www.Sva-potsam.de
20Practical technologies for reducing noise on
merchant ships
- Wake flow into propeller
- Strategies
- Wake inflow devices
- Propeller/Rudder interaction
- Improve design to hull form (only possible at
design stage) - Consider ballasting and trim for when operating
in light condition
www.algemeiner.com
21Practical technologies for reducing noise on
merchant ships
- Changes to operating procedure
- Slow steaming may reduce noise output in dB
roughly proportional to log of speed - Strategies
- May be necessary to consider redesign of
propeller for new operating speed - Revise CPP control law for low speed
22Practical technologies for reducing noise on
merchant ships
- Some technical unknowns
- Effect of modified merchant ship propellers on
hydro-acoustic noise - Effect of propeller hub caps on hydro-acoustic
noise - Effect of wake flow improvement devices on
hydro-acoustic noise - Effect of vessel loading condition on
hydro-acoustic noise - ballast, trim
- propeller close to, or piercing water surface
23Research needs and recommendations
- Development of standard method for full scale
noise measurements - ISO has been developing a standard for measuring
underwater noise from ships - ANSI/ASA agreed a standard in 2009
- Identify noisiest vessels.
24Research needs and recommendations
- Full-scale at sea noise measurements across a
range of operating conditions and types of
vessels. - Independent noise measurements are needed on
propeller design concepts or devices developed to
increase propulsive efficiency.
25Research needs and recommendations
- Increased design effort, including model testing
and CFD analysis for new ships accompanied by
noise measurements. - For ships which spend time in ballast, testing
and measurements should be extended to include
optimisation of the propeller design and wake
flow in that condition.
26Concluding remarks
- There is wide agreement that reducing shipping
noise is necessary, feasible and may become a
legal requirement in the future. - We are cautiously optimistic that the noisiest
ships can be quietened using existing technology,
whilst improving their propulsive efficiency. - The recent focus of attention on reducing
underwater noise and the clearly identified
research needs provide new opportunities in the
field of propulsion systems and ship design. - martin.renilson_at_hct.ac.ae