Download Ambient Noise Measurement Using Naval Sensors

Oceanology International 2014 – Maritime Security
Ambient Noise Measurement Using Naval Sensors
Daniel Toogood – Marine Scientist
AEUK/14/0309
Presentation Overview
• Introduction to acoustics within Royal Navy operations
• The importance of ambient noise in the marine soundscape
• Ambient noise complexity and variability
• Outline of how acoustic data is collected
• Strengths and limitations for environmental understanding
• Knowledge exploitation – Marine Strategy Framework Directive
• Data dissemination
Role of the UK Royal Navy
• Protection of UK Interests
– Sea Lanes
– Strategic Assets
– Sovereign Waters
• Maritime Security
– Piracy
– Narcotics
• International Engagement
– Humanitarian Support
– Joint Operations
• Operate in a Global Environment
– Littoral and freshwater
– Blue water and open ocean
– Extreme environments – Arctic, Antarctic
The importance of sound….
• Other energy types can’t propagate within the ocean
– Light - tens of metres, very high data rate
– High Frequency (HF) Radio – few metres
– Extremely Low Frequency Radio (ELF) – hundreds km, low data rate
• Extended range (dependent on frequency)
– 100 Hz (minimal attenuation)
– 1 kHz (0.019 dB / km)
– 10 kHz (0.19 dB / km
– 100 kHz (90 dB / km) (high attenuation)
• Acoustic waves have slow propagation
– Acoustic - 340 m/s (air)
– Acoustic – 1500 m/s (water)
– EM Waves - 300,000 km/s (air)
Understanding the environment
• Physical Oceanography
– Temperature
– Salinity
– Vertical structure
– Seastate / waves
– Bubbles
– Precipitation
– Suspended sediment
• Geophysics
– Sediment characteristics
– Seabed roughness
• Biological content
– Cetaceans
– Snapping shrimp
– Fish
• Spatial and temporal
variability
• Seasonal variation
• Daily variation
• Tidal variation
• Ambient Noise
Modelled Sound Propagation - January
Modelled Sound Propagation - February
Modelled Sound Propagation - March
Modelled Sound Propagation - April
Modelled Sound Propagation - May
Modelled Sound Propagation - June
Modelled Sound Propagation - July
Modelled Sound Propagation - August
Modelled Sound Propagation - September
Modelled Sound Propagation - October
Modelled Sound Propagation - November
Modelled Sound Propagation - December
Modelled Sound Propagation - January vs August
• Spatial variability – freshwater run off, fronts, etc
• Temporal variability – diurnal variation, ocean stratification, etc
• Optimum periods for high energy anthropogenic activity!
Wenz, 1962
Ambient Noise
• Natural
– Biological
– Geological/earthquakes
– Meteorological/oceanic conditions
– Ice
• Anthropogenic
– Offshore renewables
– Commercial shipping
– Sonar
– Acoustic deterrent devices (ADDs)
– Industry/construction/explosives
• Structure
– Continuous
– Impulsive
• Varies with:
– Frequency
– Sound speed profile
– Direction
– Time
– Sensor depth – Bottom type
– Water depth
– Sea-state
Military application of sound
• Passive sonar = ‘listening’ to underwater noise and
analysing it to discriminate natural and man-made
objects
• Active sonar = transmission of a pulse followed by
analysis of the echo
• Different objects have different
characteristics…the ‘noise’ is the background
against which the military are trying to detect,
classify and localise
• “One man’s noise is another man’s signal”….large
proportion of marine community is investigating
‘underwater noise’ rather than identifying discrete
objects
Navy Sonar Capability
• Wide bandwidth: 10s Hz 100s kHz
• Multiple transducers
arranged into arrays
• Increase signal to noise ratio
– provides ambient noise
directionality
• Some sensors can be
deployed at selectable
depth to exploit
propagation paths provides information on
noise variation with depth
• High capacity data recording
increasingly available
LF towed array
HF Diver Detection
MF Bow Array
LF towed array
HF hull array
MF bow array
MF flank array
Balance of Naval Data for Environmental Understanding
Positive
• Some regions not normally accessible by
civilian scientific vessels
Negative
• Protection of assets is the priority
• Sensors are highly accurate
• Some data would need be de-sensitised
(remove sensitive characteristics)
• Data recorded to established standard,
using detailed protocols
• Data may vary in some spatial and
temporal aspects
• Data from platform patrols are stored
• At present no established broad
distribution
• Decadal scale repetition
• Routine quality assurance
• Will continue into the future…
How could such data be useful…
• Establish longer term datasets for an area
– Acoustic soundscapes
– Shipping noise levels
– Global warming / ocean acidification (supporting environmental data)
– Baseline noise levels for areas of emerging commercial interest (arctic, deep sea)
• Supports predictive modelling
– Validation data
• Support of legislation
– Marine Strategy Framework Directive….
Ambient Noise and the MSFD
• Establish Good Environmental Status - GES
• Descriptor 11 – “Introduction of energy,
including underwater noise, is at levels that do
not adversely affect the marine environment”
• “Protect and preserve the marine environment,
prevent its deterioration or, where practicable,
restore marine ecosystems in areas where they
have been adversely affected”
• “Prevent and reduce inputs in the marine
environment, with a view to phasing out
pollution, so as to ensure that there are no
significant impacts on or risks to marine
biodiversity, marine ecosystems, human health
or legitimate uses of the sea”
Ambient Noise and the MSFD – Descriptor 11
• Ambient Noise Monitoring Programme
• Cefas (under defra funding) are currently evaluating possible ambient noise
studies
• To be coordinated via the UK Clean and Safe Seas Evidence Group (CSSEG)
– Input from the MSCC Underwater Sound Forum
– EU Technical Sub-Group (TSG)
– Project will identify suitable sources and sample data
– Then design and implementation of UK monitoring programme
• Military data could contribute!
Marine Strategy Framework Directive Consultation, January 2014. Defra. Available: Here
Dissemination Pathway
Civilian Holdings
MoD Holdings
Platform
CSSEG
Shore
• Determine GES
• Ship/sub/aircraft
• Data analysis
• Analysis
• Acoustic/
environment
sensors
• Removal of
sensitive facets
• Incorporation into
modelling/study
• Quality Control
Into Policy…
Public Data Access
• Immediate storage
• Operational
analysis
UK Data Portals
• BODC
End User…
• Model incorporation
• Wider dissemination • Further independent
analysis
Key Questions….
Key Questions
• Who pays?
• Who stores?
• Who has access?
• How is it broken down?
• Temporal/Regional composition?
• How long is data available?
Precedents Exist
• MSFD – Noise register
• UKHO Sonobuoy data
• Cetacean stranding
Contact
ATLAS ELEKTRONIK UK Ltd.
Dorset Green Technology Park
Winfrith Newburgh
Dorchester • DT2 8ZB
United Kingdom
Phone: +44 (0) 1305 212400
www.uk.atlas-elektronik.com