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Passive Sonar Detection Exercise: USS Seawolf and USS Memphis Analysis

This document outlines a passive sonar detection exercise involving the USS Seawolf attacking the USS Memphis, utilized to enhance sonar detection capabilities. It includes a series of analytical questions focusing on detection indices, thresholds, angles for nulls, directivity index, ambient and total noise levels, transmission loss, signal-to-noise ratio, and overall detectability of the Memphis. By utilizing provided data regarding submarine characteristics, bandwidth, and environmental factors, participants can derive important insights for effective sonar application.

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Passive Sonar Detection Exercise: USS Seawolf and USS Memphis Analysis

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  1. Passive Sonar Wrap Up Exercise And Exam Review

  2. Data • The two submarines described below are to engage in a sonar detection exercise off the coast of Kauai. Use the following data for all questions. • (Note: all numbers are made up and do not reflect reality.) • USS Memphis (Target) • SL of sub 180 dB in band from 100 Hz to 500 Hz • Main tonal in band = 400 Hz due to sound short of 400 Hz generator • USS Seawolf (Attacker) • Use hull array consisting of 50 hydrophones in groups of 4 spaced 30 m down the side of the sub (consider as continuous line array) • Bandwidth of sonar suite = 400 Hz from 100 to 500 Hz • Integration time of sonar suite = 20 ms • Want P(D) = 90%, P(FA) = 0.2% assume ideal sonar processor • NLself = 81 dB in band from 100 Hz to 500 Hz • Environment • Sea State = 1 • Shipping = light • transition range = 14 Kyds

  3. Part 1 • What is the detection index required for detection of the Memphis by the Seawolf? p(D)=90% p(FA)=0.2%

  4. Part 2 • What would be the detection threshold for detecting the Memphis using passive sonar? • Bandwidth of sonar suite = 400 Hz from 100 to 500 Hz • Integration time of sonar suite = 20 ms

  5. Part 3 • What are the angles for the nulls of the Seawolf’s 30 m long hull array (only give from 0 to 90)?

  6. The Angles

  7. Part 4 • What is the Directivity Index for this 30 m long array at the frequency of the principle tonal?

  8. Part 5 • What is the attenuation coefficient at the frequency of the principle tonal? f in kHz

  9. Part 6 • What is the Ambient Noise Level (Sea State and Shipping)?

  10. Ambient Noise Band Levels

  11. Part 7 • What is the Total Noise Level?

  12. Part 8 • If the Memphis were at 16,000 yds from the Seawolf, what would be the Transmission Loss (include attenuation)? transition range = ro = 14 Kyds

  13. Part 9 • If the Memphis were at 16,000 yds from the Seawolf, what would be the signal-to-noise level?

  14. Part 10 • Is Memphis detectable? If so, what is the Signal Excess? >

  15. Part 11 • What is the max detection range of the Memphis by the Seawolf (this time you can ignore attenuation)?

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