EW300 EXAM 3 - SONAR QUESTIONS + ANSWERS
1. Which sonobuoy system actively emits a signal to locate a submarine?:
DICASS
2. Directivity Index definition: the sonar receiver's directional sensitivity
3. Maximum allowable 2 way transmission loss so that an operator retains a
contact detection probability of 50% or greater is known as:: Active Figure of merit
4. Active FOI is:: the active frequency (ping frequency)
5. Target Strength is analogous to what RADAR principle?: Radar cross section
6. Main purpose of MAD (Magnetic Anomaly Detection) system: Provide a
precise location of a submarine with suflcient accuracy to permit weapons delivery
7. What considerations do you take into account when recommending active or
passive SONAR?: comparison of expected detection ranges for each mode, passive to stay covert
8. When solving for total noise for an active and passive problem, the NLAmbi-
ent value stays the same: False
9. Launched countermeasures from a submarine include: BB noise makers, generate
submarine frequencies, mobile decoys
10. Nixie countermeasure system generate bubbles along ships hull: False
11. types of Non-acoustic detection ways to detect a surfaced submarine: Visual,
RADAR, EMS, infrared imaging (FLIR)
12. Towed array of 134 m, 181 hydrophones. Max frequency?: 2014.9 Hz (fmax=v/d,
d=L/n-1)
13. Provides bearing and range: active sonar
14. average sound speed in water: 1500 m/s
15. A sound channel is formed when the SVP has this characteristic: Negative over a
positive speed gradient
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, 16. When SNR= DT there will be a: 50% chance of detection
17. these two factors dominate the SVP near the surface and deep: temperature and
pressure
18. In a negative gradient sound bends: down
19. in a positive gradient sound bends: up
20. a layer is formed by a over a gradient: positive over negative
21. SVP chart: A- depth excess
B-Critical Depth
C-Deep Sound Channel Axis
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1. Which sonobuoy system actively emits a signal to locate a submarine?:
DICASS
2. Directivity Index definition: the sonar receiver's directional sensitivity
3. Maximum allowable 2 way transmission loss so that an operator retains a
contact detection probability of 50% or greater is known as:: Active Figure of merit
4. Active FOI is:: the active frequency (ping frequency)
5. Target Strength is analogous to what RADAR principle?: Radar cross section
6. Main purpose of MAD (Magnetic Anomaly Detection) system: Provide a
precise location of a submarine with suflcient accuracy to permit weapons delivery
7. What considerations do you take into account when recommending active or
passive SONAR?: comparison of expected detection ranges for each mode, passive to stay covert
8. When solving for total noise for an active and passive problem, the NLAmbi-
ent value stays the same: False
9. Launched countermeasures from a submarine include: BB noise makers, generate
submarine frequencies, mobile decoys
10. Nixie countermeasure system generate bubbles along ships hull: False
11. types of Non-acoustic detection ways to detect a surfaced submarine: Visual,
RADAR, EMS, infrared imaging (FLIR)
12. Towed array of 134 m, 181 hydrophones. Max frequency?: 2014.9 Hz (fmax=v/d,
d=L/n-1)
13. Provides bearing and range: active sonar
14. average sound speed in water: 1500 m/s
15. A sound channel is formed when the SVP has this characteristic: Negative over a
positive speed gradient
1/7
, 16. When SNR= DT there will be a: 50% chance of detection
17. these two factors dominate the SVP near the surface and deep: temperature and
pressure
18. In a negative gradient sound bends: down
19. in a positive gradient sound bends: up
20. a layer is formed by a over a gradient: positive over negative
21. SVP chart: A- depth excess
B-Critical Depth
C-Deep Sound Channel Axis
2/7
