Th Fleet AOR, 6th Fleet AOR and 5th Fleet AOR are extremely arduous with deployable units being out of homeport well above CONUS average. Instructor Duty and Training Support Center billets can prevent a member from being in a leadership position. This fact is due to the sheer number of Chief Petty Officer and First Class billets at. ACOUSTIC REFERENCE MANUAL. Fleet and Joint activities from the Naval Meteorology. Additionally, this manual consolidates environmental. Rp 33 fleet oceanographic and acoustic reference manual pdf RP33 parameters are being considered for addition. Oceanographic and Acoustic Reference Manual, RP33, April 1999, 216 pp. Anchoita spawns. Fleet oceanographic and acoustic reference manual SECNAVINST 5510.36 DEPARTMENT OF THE NAVY (DON) INFORMATION SECURITY PROGRAM REGULATION.
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Thermocline and Mixed LayerRelationships
Shallow subsurface sound channels occur in theupper levels of the water column in the thermocline.The thermocline is the layer of sea water where thetemperature decreases continuously with depthbetween the isothermal mixed layer and the deepsound channel axis. The relative strength of a soundchannel depends upon the thickness of the channeland the maximum angle of the trapped rays.
Geographic Locations
Studies indicate that shallow sound channelsbeneath the mixed layer depth occur most often northof 40°N in the area between Hawaii and thecontinental United States. They are also frequentlyobserved in the vicinity of the Gulf Stream. Theprevalent depth of these shallow channels rangesfrom 90 to 150 meters.
During the summer a shallow channel exists in the Mediterranean Sea. In this region, the heating by the sun of the upper layers of the water, together with an absence of mixing by the wind, causes a strong near-surfacenegative gradient to develop during the springand summer months. This thermocline overliesisothermal water at greater depths. The result is astrong sound channel with its axial depth near 100meters. Although shallow sound channels are morelocal and transitory in nature, they often have astrong effect on sonar operations.
There are three graphic outputs available with theSSX product:
1. A shaded shallow sound channel axis depthdisplay. The amount of shading indicates the range ofdepth in feet. See figure 9-10.
Clear None (or depth <150 ft or >1000 ft)
Light axis depth 150-300 feet
Medium axis depth 300-600 feet
Heavy axis depth 600 – 1,000 feet
2. A shaded shallow sound channel magnitude(strength) display. The amount of shading indicates the
Figure 9-10.-A shaded shallow sound channel axis depth display.
strength of the shallow sound channel (SSC) at thosegrid points where these channels exist and meetminimal descriptive criteria. See figure 9-11.
Clear No shallow sound channels orstrength <3 ft/sec
Light Strength 3 – 5 ft/sec
Heavy Strength >-5 ft/sec
3. A shaded shallow sound channel cutoff frequencydisplay. The amount of shading indicates the limitingfrequency of the shallow sound channel. See figure9-12.
Clear No shallow channels orfrequency> 300 Hertz
Light Frequency 151 – 300 Hertz
Fleet Oceanographic Reference Manual Rp33
Medium Frequency 51-150 Hertz
Heavy Frequency 1- 50 Hertz
Figure 9-11.-A shaded shallow sound channel strength display.
Figure 9-12.-A shaded shallow sound channel cutoff frequency display.
The first portion of this chapter was devoted to thoseoceanographic products that were accessed using theNODDS.
We will now discuss phenomena and principlescovered in the Fleet Oceanographic and AcousticReference Manual, RP33. A brief overview will bepresented for each area discussed. For moreinformation, see RP33.
FORECASTING EFFECTS OFAMBIENT NOISE
LEARNING OBJECTIVES Distinguishambient noise from self-noise. Identifycharacteristics of surface ship traffic andsea-state noises.
The problem of listening for recognizable sounds inthe ocean is to distinguish them from the total noisebackground. Ambient noise is that part of the total noisebackground not due to some identifiable localizedsource. It exists in the medium independent of theobserver's activity. Interfering noise sources that arelocated on, or are a part of, the platform on which asensor is installed are sources of self-noise.
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Fleet Oceanographic Reference Manual Pdf
Click here to Order your Radar Equipment Online
Passive Sonar Equation
In passive-sonar operations, the hydrophorespickup sounds generated by a multitude of soundsources.Sonarmen must differentiate betweensoundsgenerated by a target and interferingbackgroundnoise. This process is best describedinwhat is known as the passive sonar equation.Thepassive form of the sonar equation, like theactiveform, is written using several differentsymbolsto represent the equation parameters.Oneform of the equation is as follows:
SIGNAL EXCESS. —Signal excess has thesamemeaning in the passive equation that it doesinthe active equation.
SOURCE LEVEL. —Source level pertains totarget-radiatednoise. It is the amount of soundenergygenerated by a target. The level of energyreachingthe sonar receiver depends on the typeoftarget and its mode of operation. Source levelisa function of frequency, speed, depth, andtargetaspect. The latter refers to a target'sorientationin relation to the sonar receiver.
RECOGNITION DIFFERENTIAL. —RDhasthe same meaning as in the active sonarequation.
NOISE LEVEL. —The definition for NL inthepassive equation is the same as in the activeequation.Passive sonars may be ambient-noiseorself-noise limited. These sonars lessen the noiseincertain frequency ranges, thereby permittingatarget signal to be more readily detected.
Ambient Noise. —Ambient noise is thatpartof the total background noise created bysurface-shiptraffic, wave action, precipitation,ice,and certain forms of marine life.
Self Noise. —Self noise is that part of the totalbackgroundnoise attributable to the sonar equip-ment,theplatform on which it is mounted, or thenoisecaused by the motion of the platform. Themajorclasses of self-noise are machinery noise,propellernoise, and hydrodynamic noise. Thelatterresults from the flow of water pasthydrophores,supports, and the hull structure oftheplatform.
DIRECTIVITY INDEX. —DI has the samemeaningas in the active sonar equation.
PROPAGATION LOSS. —PL has thesamemeaning as in the active sonar equationexceptthat with passive sonar, the energy loss isone-way.
References
Fleet Oceanographic And Acoustic Reference Manual Pdf
strength of the shallow sound channel (SSC) at thosegrid points where these channels exist and meetminimal descriptive criteria. See figure 9-11.
Clear No shallow sound channels orstrength <3 ft/sec
Light Strength 3 – 5 ft/sec
Heavy Strength >-5 ft/sec
3. A shaded shallow sound channel cutoff frequencydisplay. The amount of shading indicates the limitingfrequency of the shallow sound channel. See figure9-12.
Clear No shallow channels orfrequency> 300 Hertz
Light Frequency 151 – 300 Hertz
Fleet Oceanographic Reference Manual Rp33
Medium Frequency 51-150 Hertz
Heavy Frequency 1- 50 Hertz
Figure 9-11.-A shaded shallow sound channel strength display.
Figure 9-12.-A shaded shallow sound channel cutoff frequency display.
The first portion of this chapter was devoted to thoseoceanographic products that were accessed using theNODDS.
We will now discuss phenomena and principlescovered in the Fleet Oceanographic and AcousticReference Manual, RP33. A brief overview will bepresented for each area discussed. For moreinformation, see RP33.
FORECASTING EFFECTS OFAMBIENT NOISE
LEARNING OBJECTIVES Distinguishambient noise from self-noise. Identifycharacteristics of surface ship traffic andsea-state noises.
The problem of listening for recognizable sounds inthe ocean is to distinguish them from the total noisebackground. Ambient noise is that part of the total noisebackground not due to some identifiable localizedsource. It exists in the medium independent of theobserver's activity. Interfering noise sources that arelocated on, or are a part of, the platform on which asensor is installed are sources of self-noise.
[ Back ][ Home ][ Up ][ Next ]
[ Back ][ Home ][ Up ][ Next ]
Fleet Oceanographic Reference Manual Pdf
Click here to Order your Radar Equipment Online
Passive Sonar Equation
In passive-sonar operations, the hydrophorespickup sounds generated by a multitude of soundsources.Sonarmen must differentiate betweensoundsgenerated by a target and interferingbackgroundnoise. This process is best describedinwhat is known as the passive sonar equation.Thepassive form of the sonar equation, like theactiveform, is written using several differentsymbolsto represent the equation parameters.Oneform of the equation is as follows:
SIGNAL EXCESS. —Signal excess has thesamemeaning in the passive equation that it doesinthe active equation.
SOURCE LEVEL. —Source level pertains totarget-radiatednoise. It is the amount of soundenergygenerated by a target. The level of energyreachingthe sonar receiver depends on the typeoftarget and its mode of operation. Source levelisa function of frequency, speed, depth, andtargetaspect. The latter refers to a target'sorientationin relation to the sonar receiver.
RECOGNITION DIFFERENTIAL. —RDhasthe same meaning as in the active sonarequation.
NOISE LEVEL. —The definition for NL inthepassive equation is the same as in the activeequation.Passive sonars may be ambient-noiseorself-noise limited. These sonars lessen the noiseincertain frequency ranges, thereby permittingatarget signal to be more readily detected.
Ambient Noise. —Ambient noise is thatpartof the total background noise created bysurface-shiptraffic, wave action, precipitation,ice,and certain forms of marine life.
Self Noise. —Self noise is that part of the totalbackgroundnoise attributable to the sonar equip-ment,theplatform on which it is mounted, or thenoisecaused by the motion of the platform. Themajorclasses of self-noise are machinery noise,propellernoise, and hydrodynamic noise. Thelatterresults from the flow of water pasthydrophores,supports, and the hull structure oftheplatform.
DIRECTIVITY INDEX. —DI has the samemeaningas in the active sonar equation.
PROPAGATION LOSS. —PL has thesamemeaning as in the active sonar equationexceptthat with passive sonar, the energy loss isone-way.
References
Fleet Oceanographic And Acoustic Reference Manual Pdf
Fleet Oceanographic and Acoustic ReferenceManual, RP-33, Naval Oceanographic Office,July1986.
Operational Oceanography Module II, AcousticsandSound Ray Theory, NOCF Bay St. Louis,Miss.,1988.
Rp 33 Fleet Oceanographic Pdf
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