Second test Flashcards
What can affect sound propagation?
Temperature, Salinity, Water and pH (water chemistry)
How much faster does sound travel in air than water?
5 x
Low frequency
Long wavelengths, travel further than high frequency
High frequency
Short wavelengths, travel shorter distances than low frequency
What are natural sources of noise?
Earthquakes, Ice, Turbulence, Breaking waves, Rain, Bubbles and spray, Marine life
Shipping noise
5-500Hz (low frequency) caused by propellers, flow noise, engine noise and dynamic positioning.
Seismic surveys
High energy sound sent into the seabed to locate oil/layout of seabed. Under 300Hz, but can be up to 15kHz.
Naval Activities (Sonar)
High energy, low (100-500Hz), high (2-8kHz). Used for submarine locating, causes the bends.
Fisheries and Side-scan sonars.
Use Acoustic Doppler Current Profiler (ADCP) which measure ocean currents. High frequency.
Acoustic Thermometry of the Oceans Climate (ATOC) was used.
ADCP
Acoustic Doppler Current Profiler
ATOC
Acoustic Thermometry of the Oceans Climate - used for determining accuracy of acoustic methods in measuring large scale changes to temperature and heat content, as well as effects on marine mammals.
Construction
Detonations for pile driving (for off-shore wind farm constructions). 100Hz - 10kHz and causes displacement.
Fisheries
Use sonars to locate fish as well as deterrents to scare marine mammals away.
Impacts of noise disruption on marine mammals
Death through the bends/stranding, injury, PTS/TTS, increased stress, change in behaviour and masking.
PTS/TTS
Permanent/Temporary Threshold Shift. Small sounds which could once be heard can no longer be.
PTS occurs from pile driving within about 5m cetaceans 20m pinnipeds.
TTS = 10m cetaceans, 40m pinnipeds.
Not all animals PTS/TTS zones are known
