ProblemSet6_2011 - E53 00 Principles of Naval Weapon...

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Unformatted text preview: E53 00 Principles of Naval Weapon Systems Problem Set 6 - AY2011 NAME: KC" Instructor/Section / 1) Draw at least four (4) sound “rays” propagating away from the noise source showing the path of propagation for the given velocity gradients. (Hint: Waves are lazy.) Sound Velocit Noise Source Noise Source Depth Depth 2) Given a Propagation Loss Curve and the Transmission Loss Estimate formula: a) Which is the more accurate measure of signal loss? Pmpqd qi—Cm L05; Curve. b) What information is makes it more accurate? sup, smaoar (an iv» 3) In the Transmission Loss Estimate formula, which term(s) account for the following losses of sound energy associated with SONAR operations? Range <= 1000 meters Range > 1000 meters a. Scattering: A A b. Absorption: 0" {L 0‘ R c. Spreading: 2.0 lo; (2) i10 b; CR) 4 30 d. Why does the formula change at 1000 meters (explain both the change in general and why it is at 1000m in particular)? 0 Hint C “’7‘ Fm“ SP“ '1‘“ id Cy,“ éi-‘rql 5ft 9.. Jfij “Nth What depth does this M acm- Agni» on,“ row in. formula assume for the woe» $569.. ( ) ocean. 4) Consider the following environmental factors on sound speed in water: Temperature (T), Pressure (P) and Salinity (S)... a) In the surface layer, which factor dominates? Why? P"’5”'c/ 7'"? (flai'm‘i’ m 5w‘Fue. [‘7‘]— duo l6 Mle‘flj. b) In thermoclines (permanent and seasonal), which factor dominates? Why? T'fl?¢, fire, T." PUfi'i"/L dam W‘ykx . c) In the deep isothermal layer, which factor dominates? Why? m 5.5441134! raw”. mew. 7'"? Web" 1 ES300 Principles of Naval Weapon Systems 5) Given the Sound Velocity Profiles (SVP) below indicated by the dashed line: 3) Draw at least five ray paths originating from the sound source (submarine). Identify any of the following predominating features: Convergence Zone, Sound Channel, Sonic Layer Depth, Shadow Zone, Depth Excess, Surface Duct, Half Channel. C Range C Range \\ r... ,2\ 5L) \\ Aa/IJ’ES/ I 6) Given: An underwater target at range of 8,500 m. You have both passive and active SONAR; your passive frequency = 2400 Hz and your active frequency = 20 kHz. The environment’s measured Transmission Loss Anomaly (A) is 9 dB. a) Calculate the transmission loss due solely to absorgtion (i.e., neglect spreading and scattering): (1) For the passive target frequency: ‘_>_ “6 _ 0, 7 (3.0%, 4’; +31, 0.0% (2,4); 4-, IL)":— 594 MO 3:, 9 “Int: A / ‘ 9”” g 5 '47'Lw (Z l Calculate afor this question thaw cw * / even though f<3kHz ,5 ‘ _ ’2 . P324 4.236,qu (ism-w (2) For the active transmitting frequency: Q 9 '5. Lard)? 20‘) L” 0'00‘17?” trim/mm / P olfl:0.oo‘5‘7lb’rgsd‘):{a’l'7 46 t ’49 0 Pitfall Preventer: don’t forget to include (3) Calculate the total transmission loss estimate for BOTH active and passive: ZTLr = 2 C") /°f](9r)i’5o +Jl'2 Hi) the transmission loss for the entire round trip. ES3 00 Principles of Naval Weapon Systems 7) As the ASWO, you are preparing your ASW system for training operations adjacent to Shipping Lanes near the island of Santa Catalina off Los Angeles. You are training with a submarine with a known acoustic signature of 350 Hz (radiated from its feedwater pump.) Surface sea conditions are rough with a Sea State of 4. In addition, a pod of migrating dolphins are discussing their winter break plans and producing a noise level of 62 dB at 2000 Hz. a) What is the total Ambient Noise at the target’s frequency of 350 Hz? 3’0 42 @954: genres/Jug O - £3 \3/ > '10 0’" 5,5 (2,4 ‘_ H=ée io (ofi’lo HO V61? b) If your ship’s speed is 14 knots, what is the Self Noise for your ship? 0 Hint_ go A E Use the self noise chart on page 11 of your appendix. c) What is the total Noise Level? 6 1 1 ’ éfid‘J’éo west/:6“ 5-“ loluyflo'H/otfligfléfi V d) Label the following elements of noise as either broadband or narrowband: (1) The migrating dolphins: yf; (2) The ocean traffic: 5 p? (3) The hydrodynamics: P7 [5 (4) The submarine’s electric generator: IV (5) Your ship’s flow noise: ii Which noise in art d is considered “hull noise?’.’ ‘ v ) p LL!) @L’C‘lr (c, Jalef‘u‘l‘dr‘ iii) List at least two ways that you might reduce your ship’s flow noise: SID/J (kW/""3 C. fem Lia H 8) Assume your passive SONAR has a FOM value of 38 dB at 1 kHz during the day. a) Showing proper use of the one-way PROPLOSS curve below, at what range(s) can you detect a 1 kHz target? 0~ Z , l?) “/ 77 K I”) b) What propagation path corresponds to Ie‘ach of these ranges? " l5 .5 c) How high does your FOM need to be to achieve CZ propagation? 1'] J D . V . .... .. V . . 1 Propagation Loss (dB) $5 11'. 2.3 50 55 EC 35 TE .‘5 9] 2!: Range {km} E8300 Principles of Naval Weapon Systems 9) Define Figure of Merit (FOM): Given the following: Own ship: Target: Source level: 200 dB Source Level: 140 dB Frequency: 3.2 kHz Frequency: 600 Hz Self Noise @ 600 Hz: 75 dB Target Strength: 30 dB - 2CD 5 SelfNoise @ 3.2 kHz: 45 dB Range: 10,000 m @62 L95 ; Directivity Index Active: 15 dB V5 Directivity Index Passive: 18 dB 67"" v5 Detectlon Threshold: 4 dB 65+; at? Environment: 15+]: 14:16 Operating Area: Heavy Traffic Transmission Loss Anomaly (A): 8 dB 03".“, (My, Sea State: 2 Reverberation level: 42 dB Narwhales 62 dB @ 600 Hz Biologics: Sea snakes 65 dB @ 3.2 kHz 21) For Passive operations: ‘ i) Calculate the FOMP: 1600 He ; zg ‘43 V 9r“ “’07 e ‘ JBCAWLAM- o ff meleemwys'ls-S , _ .z r ‘ ' p A / HO 75,5 + '3 ‘/ 13,5 >7 0 0””6 “"0" “’9- '"(O- }L PIX"! 3 fAM HI ‘3’ ii) Calculate the estimated Transmission Loss the signal will experience at the given range: Tlp:l0103(12)*’30 'i'O‘IZ “Q (wield/e ’d ’0 ., 10 lo )0 my) «’50 + 0 + K '79-’90“) «4 ‘ 3 A 6 iii ow w et er the probability of detection for passive SONAR operations is greater than 50% FO‘M‘or 175 7 :TLP «A605. Fofip .?3:73-TLP I a ' \ €07 c‘vufc O — t . A ' (buwfi’wizi 0 o gci+ef m‘ S L) A d ‘9 {1°C *‘ O do‘l'Fc'I‘t‘am M“. b) For Active SONAR operations: i) Use calculations to prove whether you are Noise-Limited or Reverberation-Limited: Mp1» ass :5 550% 7 ‘12 " ’21 {a woe flew-J6 ’a—I' [5: o i -\ «7 0" 0 00 /l/o;)¢ im.‘7l9é' 5 ac) H»S$ ii) Calculate the FOMA: [50%; s L +f$~N1L+Dl’DT :univsav43%+1S-# isi737432 iii) Calculate the estimated Transmission Loss the signal will experience at the given range: ZI’L,‘r : 2 (to [0301) rgo rel/Z +A) ‘0, 3; kHz / ‘ ' 2; .“l r3O’1-hoSKIOL‘0QOch r 25) O“; OwALd-Mb—(Ygé) , hos-mo T j Law/)1, +3600 iv) Show whether the probability of detection for active SONAR operations is greater than 50%: Folk: H.531 ) 15%.) :ZTLA 000 Beiifi‘ i ‘1‘“ 66% JB'F’Cind/l /,/——-—’-"-.—"._—_- 4 ...
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This note was uploaded on 02/09/2012 for the course WEAPONS AN ES300 taught by Professor Blood during the Summer '11 term at Naval Academy.

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ProblemSet6_2011 - E53 00 Principles of Naval Weapon...

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