Day 1 Flashcards
Diesel +/-
Very quite on batteries, Must snort
Nuclear +/-
Range, speed, endurance
Constant noise
Snort order
- ESM
- Periscope
- Snort
- Maybe comms/radar
Reasons to surface
Attack solutions
Emergencies
Comms
Snort
5 Sub Prop modes
DE, BATT, TR, TE, AIP
Surface prop modes
DD, DR
Definition of sound
A periodic variation in pressure, particle displacement, or particle velocity in a elastic medium
Definition of frequency
Number of full cycles passing a fixed point in one second, measured in Hz
What is effective pressure?
The average value of acoustic pressure, root mean square (RMS)
What is SPL?
Sound pressure level (sound intensity)
2 parts of periodic variation
Rarefaction + compression
Linear change of 2x the source
3dB
Linear change of 5x the source
7dB
Linear change of 100x the source
20dB
2 underwater detection categories
Active + Passive
Topography
Shelf, Slope, Rise, Abyssal plane, trench, Seamount/ridge
Bottom composites
Sand - Fairly good reflector, fairly smooth
Rock - V good reflector, often irregular
Mud/silt - Extremely smooth, poor reflector, bellow 300Hz may refract
Ooze - mud with high carbonate content
Choke point
geographical features, above or below surface, that restrict freedom of movement of a submarine
2 types of propagation loss
Spreading
Attenuation
2 types of spreading
Spherical - 2x distance = lose 6dB
Cylindrical - 2x distance = lose 3 dB
4 types of attenuation
Absorption - loss of energy due to molecular action
Scattering - reflection from surface, bottom, suspended
particles
Duct leakage - sound energy leaks outside of duct
Deep scattering layer - layer made of plankton/marine life, rises at sunset, lowers at sunrise due to temp
Ambient noise
any noise not target related
2 types of ambient noise and sub-sections
Manmade- drilling, seismic survey, shipping, sonar
Natural - biological, ice, sea state, precipitation
