18 - Acoustic Noise

Question 1

What is Broadband?

Answer 1

Gives off a wide range of frequencies
- Propellors / Shafts
- Flow noise over ship’s hull
- Ship’s propulsion system
- Ocean traffic

EO analogy: thermal radiator

Question 2

What is Narrowband

Answer 2

Gives off a specific frequency
- Pumps
- Motors
- Electrical generators
- Propulsion engines

EO analogy: selective radiator

Question 3

Broadband Display traits

Answer 3

• Bearing v. Time
• All sounds with high db Source levels

Visual Nav Comparison: You see light with the naked eye

Question 4

Narrowband Display traits

Answer 4

• Frequency v. Time
• All frequencies down a selected bearing

Visual Comparison: using binoculars to enhance vision to better classify

Question 5

What are the different types of Frequencies of Interest (FOI) ?

Answer 5

• Active
• Passive

Question 6

What is Active FOI?

Answer 6

Own ships active transmission frequency
- Usually in kHz

Question 7

What is Passive FOI?

Answer 7

Narrowband frequency of a man made components
- Usually in 100s of Hz

Question 8

What is BOSH?

Answer 8

• Biological
• Ocean Traffic
• Seismic
• Hydrodynamic

Used to calculate NL_Ambient (Other noise)

Question 9

Sources of Self Noise (N_self)

Answer 9

• Machinery Noise
• Flow Noise
• Cavitation