Analysis and Ranking of the Acoustic Disturbance Potential of ...

More documents

Recommendations

Info

FIG. 4.1 CORRECTION TO 300 M REFERENCE SPECTRA FOR AIRCRAFT FLYOVER AT $ OTHER ALTITUDES (Standard Day conditions) cr q 1 . 1 . P . z 0 Q\ a Cr V1 I * . I ' . m 0 0-- C m -I= I 0 m & F z c 8 V1 0 -lo-- -e 1 km L 0 0 -20-- L 1 C3 8 '? * 20 40 80 160 315 630 1250 2500 5000 10000 % p 1/3 Octave Band Center Frequency I a 2 0 i? T. (D cn
Report No. 6945 BBN Systems and Technologies Corporation be used with the TL spectra in Fig. 4.1 to estimate received levels near the ground. Examples of this procedure are presented in Sec. 5.3. 4.2 Underwater Sound Transmission In unbounded deep water sound transmission characteristics are determined by geometric spreading loss and molecular absorption of the sound energy in the same manner as in atmospheric transmission. Molecular absorption losses are much smaller underwater, however, and are not significant for frequencies less than 5 kHz and ranges less than 5 km. Sound transmission in shallow water is.influenced by reflection losses from the bottom and surface, refraction from sound speed gradients, reflection and refraction from subbottom layers, and scattering from rough surfaces. All these effects must be considered along with geometric spreading loss to obtain estimates of the received level at some distance from a source. The large variability in temperature and salinity characteristics of Alaskan coastal waters has a significant influence on sound propagation. Two representative sound speed profiles are shown in Fig. 4.2. The strong surface layer condition occurs in many areas during July - September when solar heating is high. The higher temperature region near the surface is associated with a lower salinity layer produced by runoff from rivers which floats on top of the denser ocean water. While the sound speed in fresh water is slower than that in ocean water, the temperature difference near the surface more than compensates for the effect of the lower salinity. Since sound travels faster in warm water than cold, the net effect is a downward refraction of horizontally traveling sound rays. This produces more bottom reflections per kilometer and higher transmission loss than would be the case if the high sound speed surface layer did not exist. During the period of November - May when the surface is generally colder than the water at depth, the sound speed profile tends toward the neutral condition shown in Fig. 4.2. Under these conditions sound is not refracted downward and the influence of the bottom on the transmission loss is reduced. In ice-covered areas, the colder region near the surface produces upward refraction so that the ice layer roughness often becomes a more significant influence in sound transmission loss than the bottom properties (Milne 1967). Several analysis techniques and computer-based mod-els have been developed to aid in the prediction of acoustic transmission loss characteristics (Miles et al. 1987; Malme, Smith and Miles 1986). These procedures use measured sound speed profiles, bottom-loss parameters, and surface loss parameters in addition to spreading loss calculations to obtain their results. Several models have been developed for Navy applications such as the Generic Sonar Model (Weinberg 1985). Most of these are intended primarily for application to deep water areas. However, a recently developed model which is based on a procedure for solving the parabolic wave equation (Lee and Botseas 19821, can be applied to shallow water transmission. Moreover, it has provision for range-dependent parameters such a a sloping, non-uniform bottom, and rangevarying sound speed profiles. This l'Implicit Finite-Difference (IFD) Computer Modeln developed at the Naval Underwater Systems Center was used to compute
Page 1 and 2:
BBN Svstems and Technologies Cor~or
Page 3 and 4:
Report No. 6945 BBN Systems and Tec
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 18 and 19:
Page 20 and 21:
H BOWERS BAW I ALEUTIAN ARC 3 STGEC
Page 23 and 24:
Page 25:
Page 29 and 30:
Page 31 and 32:
A BEAUFORT SEA B U WCH SEA CHOPEaAS
Page 33 and 34:
Report No. 6945 L 1 A. Baird's Beak
Page 36 and 37:
Page 38 and 39:
A BEAUFCRT SEA B CHW(CH SEA CHOPEBA
Page 40 and 41:
A BEAUFCRT SEA BWKQIYA DrnTONBAsw E
Page 42 and 43:
A BEAUFORT SEA BCHlKCHSEA CHaeEansr
Page 45 and 46:
on the ice. The single calves remai
Page 47 and 48:
A 0EAUFaAT SEA BCHJKCH 9 A CHaPE BA
Page 49 and 50:
BCmrcCHSEA CHOPEBnsw 0 NORTON 0Am E
Page 51 and 52:
.. A BEWORT SEA B WKCH SEA CH)PEBAS
Page 53 and 54:
Report No. 6945 BBN Systems and ~ec
Page 55:
Page 58 and 59:
l fjG 1 ll.1 16:' 1 GI) 158 15.1 1
Page 60 and 61:
Report No. 6945 BBN Systems and Te~
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Table 2.8. Characteristics of Under
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Report No. 6945 BBN Systems arid Te
Page 80 and 81:
Page 82 and 83:
Report No'. 6945 BBN Systems and Te
Page 84 and 85:
Report No. 6945 , BBN Systems and T
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93: Report No. 6945 BBN Systems and Tec
Page 102 and 103: Report No, 6945 BBN Systems and Tec
Page 104 and 105: Report No. 6945 BBN systems and Tec
Page 106 and 107: FIG. 3.2 NOISE SPECTRA IN SHALLOW W
Page 112 and 113: Adapted From K.H. Jacob (1986) Cali
Page 114 and 115: FIG. 3.8 ESTIMATED OVERALL SOUND LE
Page 118 and 119: FIG. 3. Q UNDERWATER NOISE SPECTRA
Page 124 and 125: FIG- 3.1 1 STATISTICAL ANALYSIS OF
Page 126 and 127: FIG- 3-12 STATISTICAL ANALYSIS OF C
Page 128 and 129: -- Alr Gun Array + Vlbrosels -* Ice
Page 132 and 133: FIG. 3.14 REPRESENTATIVE SHIPS AND
Page 134 and 135: BBN Systems and Technologies Corpor
Page 136 and 137: ~ -- -- FIG. 3.1 7 REPRESENTATIVE R
Page 138 and 139: FIG. 3-18 REPRESENTATIVE CULTURAL S
Page 152 and 153: A. 6. ~la~onca 011shwe. mm I C. MSI
Page 154 and 155: Report No. 6945 BRN Systems and Tec
Page 160 and 161: FIG. 4.1 1 AIR TO SHALLOW WATER SOU
Page 164: Report No. 6945 BBN Systems and Tec
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
~epbrt No. 6945 BBN Systems and Tec
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Report No. ,6945 BBN Systems and Te
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Report No. 6945 BBN Systems and ~ec
Page 257 and 258:
Page 259 and 260:
Report No. 6945 - BBN Systems and T
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275:
Page 278 and 279:
Page 280 and 281:
Report No. 6945 FIG. C. 1 A BBN Sys
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
FIG. D. 1 HUMAN VOCALIZATION AND AU
Page 288 and 289:
FIG. D. 3 ESTIMATED HEARING CHARACT
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304:
show all

Analysis and Ranking of the Acoustic Disturbance Potential of ...

Create successful ePaper yourself

Delete template?

Save as template?