L5: Human Noise Flashcards
Why is sound important in the sea?
Sound travels 5x faster underwater than in air.
Light penetrates only to shallow depths
- Sound is the main sense fro marine organisms.
True or False
Lower frequencies travel further than high frequencies?
True
Speed of sound changes with….
Temperature
Salinity
Density
What is the optimum sound level called?
Sound Channel
- were sound travels best
Deep Sound Channel
Sound waves in this layer get ‘trapped’ between water layers
Near Bermuda (1000 m)
Shallower in Temperate water
Beyond 60 degrees North or South it reaches the surface
Therefore if you put more noise in the Arctic and the Antarctic it is going to disperse around the world in this sound channel.
Sound can travel for how many kilometers?
> 1000 km
What are the Human noises in the sea?
Shipping
Seismic surveys
Naval activities (sonar)
Recreation
Science
Fisheries
Construction
Shipping Noise
Propeller cavitation, flow noise, engine noise.
Contributes 5 - 500 Hz (Low frequencies)
Has increased LF noise to the ocean at a rate of 3dB / decade (doubling every decade)
Seismic Surveys
Airgun - sends high energy sound into the seabed to find oil, determine seabed, etc.
Sound concentrated <300 Hz but energy spills out into higher frequencies (up to 15 kHz).
- Affects a wider range of species
Naval Sonar
Use high energy mid-low frequency sonar to find submarines
Low frequency (LFA) = 100 - 500 Hz
Mid frequency (MFA) = 2 - 8 kHz
Been linked to the most serve effects or impacts on marine mammals (deep diving species)
- Beaked whales come up to surface with the bends.
Construction
Pile Driving
- Offshore wind farm construction
- Very loud noise
- 100 Hz - 10 kHz
Temporary displacement of marine mammals (porpoises)
- big wind farms can exclude animals for long periods.
What does ADD stand for?
Acoustic Deterrent Device
Fisheries
Sonar to find fish
Acoustic deterrents / pingers to scare away marine mammals from nets.
Science
Side-scan sonar
Fisheries sonar
ADCP (high frequency)
Depth Sonars
ATOC - Acoustic Thermometry of the Oceans Climate
Play-back experiments
Noise is classed as pollution under what legislation?
EU Marine Strategy Framework Directive (MSFD)
What does IMO stand for?
International Maritime Organisation
What are EIAs?
Environmental Impact Assessments
Widest hearing range?
Marine Mammals
Impacts
Sounds are audible but don’t disturb
Cause disturbance
Cause displacement (temporary or permanent)
Mask communication / navigation sounds
(Start to get damage below)
Cause Temporary Threshold Shift (TTS)
Cause Permanent Threshold Shift (PTS)
Cause injury
Cause Death
What does TTS stand for?
Temporary Threshold Shift
What does PTS stand for?
Permanent Threshold Shift
What do the effects of noise pollution depend on?
Hearing sensitivity of species
Distance from sound source
Behavioral sensitivity
What are the difficulties in measuring hearing sensitivity?
Need captive animals
Limits species you can study
Can’t simulate depth
Fill in the blanks
PTS within (__m)(cetaceans) and (__m)(pinnipeds)
TTS within (__m)(cetaceans) and (__m)(pinnipeds)
Ensure no animals within TTS range (___m)
PTS within (5m)(cetaceans) and (20m)(pinnipeds)
TTS within (10m)(cetaceans) and (40m)(pinnipeds)
Ensure no animals within TTS range (100m)
