Lesson 3 Flashcards
(15 cards)
What is the speed of sound in water?
1500m/s (average)
What can effect acoustic velocity?
Temperature
Pressure
Salinity
How much does temperature affect AV?
3 m/s increase per an increase of 1 degree C
How does pressure effect AV?
2m/s increase as pressure increases 100m
How does salinity effect AV?
1.1 m/s increase as salinity increases 1 part/1000
When is iso velocity water found?
When it decreases at a rate of 0.6 degrees C per 100m
Temperature change cancelled out by Pressure changes
What is the model we use for ocean layers called?
3 layer ocean model
Explain the 3 layer ocean model
X axis = temp
Y axis = depth
1st layer = mixed layer
2nd layer = permanent thermocline
3rd layer = deep water
What is the mixed layer?
Water warmed by sun and mixed by wind/waves
What is the permanent thermocline layer?
Usually a pronounced negative temperature gradient
What is the deep water layer?
Generally cold isothermal layer
What rule do we use for refraction?
HALT!
What does HALT stand for?
High away, low towards
Rays attempt to refract away from high sound velocity to lower sound velocity areas
What is reflected energy?
Usable sound energy of which up to 99% is reflected from surface or sea bed
What is critical angle?
Critical angle is the steepest angle in which there is 100% reflection from the bottom or surface
