[WIP] thermocline refraction effect

[castorp345]

in sim.cfg the value ranges given for thermal layer signal attenuation are, for passive sonar, "3 equals signal reduction to 33%", and for active sonar "5 equals signal reduction to 20%". assuming the sound energy source is proceeding from 45deg, it appears that a 'nominal' median for the angle of refraction should be c22.5deg (see == http://www.eugeneleeslover.com/USNAVY/CHAPTER-28-A.html and the diagram under section 28A4 "The Limitations of Sonar"). since attenuation corresponds to the angle of refraction i'd suggest using the same value--22.5deg--to determine at least the passive sonar's signal attenuation value: 1.7032 (as opposed to the original sim.cfg's '3'=33%).
active sonar is a little more difficult and i'd certainly welcome further input here... i'm assuming that the higher energy level of a focused 'ping' results in less apparent attenuation, but the question is to what order?

[edit: fixed botched math ]

[Bill Nichols]

Of course, active sonar has to cross the thermocline twice, so the amount of attenuation is compounded compared to the passive case.

[castorp345]

Originally Posted by Bill Nichols

Of course, active sonar has to cross the thermocline twice, so the amount of attenuation is compounded compared to the passive case.

of course!

thanks Bill!

[castorp345]

ok, after some further examination i've come up with what seems to be more "reasonable" numbers:

[edit: probably not , still tbd]

for passive, Thermal Layer Signal Attenuation=1.7032 ; where '1' means no signal reduction and '3' equals signal reduction to 33%, then '1.7032'=signal reduction by 22.5% (ie the angle of refraction assuming a 45deg initial source)

for active, Thermal Layer Signal Attenuation=2.0078 ; where '1' means no signal reduction and '5' equals signal reduction to 20%, assuming a HF pulse of 35KHz and max 'nominal' emmissions of c20KHz gives a modifier of 1.75 which, when compounded (to account for crossing the thermocline twice), produces '2.0078'=signal reduction by 19.69% (apparent attenuation)

(if anyone has more accurate Hz values for japanese sonar of this time period i'd love to know!)

[PeriscopeDepth]

Japanese sonar frequencies can be found in here http://www.fischer-tropsch.org/prima...ort%20E-10.pdf

PD

[castorp345]

thanks PD!