Sound in the Ocean

Question 1

Name noise sources that can affect measurements

Answer 1

• Natural physical noise
• Biological noise
• Manmade noise
• Platform noise
• System noise
• Source noise (reverberation)
• Signal processing artifacts

Question 2

Name prevailing sources of ambient noise

Answer 2

• Wind and wave driven noise
• Earthquakes
• Rain
• Bubbles and spray
• Sea ice
• Biological’s

Question 3

Examples of how fish produce noise

Answer 3

• Muscular stridulation of the swimbladder + bladder resonance
• Scraping of fin-ray prominences in a “comb-tooth stridulation”
• Mastication by throat-teeth + swimbladder resonance
• Grinding of food using palatal teeth
• Chopping and biting of coral or crustacea
• Body movements disturbing gravel - water being pushed around creates pressure waves
• Possibly hydrodynamically generated noise

Question 4

Examples of Explosives

Answer 4

• Rock excavation,
• Demolition / decommissioning
• Preparation for foundations,
• Structural (harbours, piers, bridges)
• Deepening channels
• Dike construction / removal
• Fishing
• Geophysical exploration,
• Military operations …. disposal, active

Question 5

What is special about snapping shrimp?

Answer 5

The sounds they make are sharp transients ( generate very broadband frequencies)

Sound comes from bubbles they make by shutting and clapping their claws

Cavitation - gas dissolved in liquid comes out
Snapping - negative pressure is created

They appear to oscillate due to
- ambient pressure trying to get rid of the bubble
- conservation of momentum makes it look like bubble is reappearing as it pushes back

Question 6

Definition of a shock wave

Answer 6

rapid intense pressure wave

sonic boom

when something travels faster than speed of sound