L5: Human Noise

Question 1

Why is sound important in the sea?

Answer 1

Sound travels 5x faster underwater than in air.
Light penetrates only to shallow depths
- Sound is the main sense fro marine organisms.

Question 2

True or False
Lower frequencies travel further than high frequencies?

Answer 2

True

Question 3

Speed of sound changes with….

Answer 3

Temperature
Salinity
Density

Question 4

What is the optimum sound level called?

Answer 4

Sound Channel
- were sound travels best

Question 5

Deep Sound Channel

Answer 5

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.

Question 6

Sound can travel for how many kilometers?

Answer 6

> 1000 km

Question 7

What are the Human noises in the sea?

Answer 7

Shipping
Seismic surveys
Naval activities (sonar)
Recreation
Science
Fisheries
Construction

Question 8

Shipping Noise

Answer 8

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)

Question 9

Seismic Surveys

Answer 9

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

Question 10

Naval Sonar

Answer 10

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.

Question 11

Construction

Answer 11

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.

Question 12

What does ADD stand for?

Answer 12

Acoustic Deterrent Device

Question 13

Fisheries

Answer 13

Sonar to find fish
Acoustic deterrents / pingers to scare away marine mammals from nets.

Question 14

Science

Answer 14

Side-scan sonar
Fisheries sonar
ADCP (high frequency)
Depth Sonars
ATOC - Acoustic Thermometry of the Oceans Climate
Play-back experiments

Question 15

Noise is classed as pollution under what legislation?

Answer 15

EU Marine Strategy Framework Directive (MSFD)

Question 16

What does IMO stand for?

Answer 16

International Maritime Organisation

Question 17

What are EIAs?

Answer 17

Environmental Impact Assessments

Question 18

Widest hearing range?

Answer 18

Marine Mammals

Question 19

Impacts

Answer 19

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

Question 20

What does TTS stand for?

Answer 20

Temporary Threshold Shift

Question 21

What does PTS stand for?

Answer 21

Permanent Threshold Shift

Question 22

What do the effects of noise pollution depend on?

Answer 22

Hearing sensitivity of species
Distance from sound source
Behavioral sensitivity

Question 23

What are the difficulties in measuring hearing sensitivity?

Answer 23

Need captive animals
Limits species you can study
Can’t simulate depth

Question 24

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)

Answer 24

PTS within (5m)(cetaceans) and (20m)(pinnipeds)
TTS within (10m)(cetaceans) and (40m)(pinnipeds)
Ensure no animals within TTS range (100m)

Question 25

What are the different changes in behavior?

Answer 25

Displacement (move away from sound)
Change in movement
Change in vocalisations
Change in surface patterns

Question 26

Mitigation

Answer 26

‘Ramp-up’ of sound levels (gives animal chance to move away)
MMOs - Marine Mammal Observers on Naval and Seismic vessels (stop when animals seen/heard
Acoustic deterrents
Avoidance of critical times / locations to animals (e.g. avoiding breeding grounds or times of breeding / feeding)
Monitoring (determine impact and increase in noise)

Question 27

Mitigation Examples

Answer 27

Bubble Curtains (reduce noise levels) (only work if weather is appropriate, not too deep and if you haven’t got high tidal currents)
Stop and/or move activities
- E.g. Northern Right Whales inability to move in response to ship noise = shipping lanes moved.