[Ns-bugs] [Bug 1055] Possible bug at the UAN's Thorp absorption loss model

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=1055

Salva Climent <jocliba at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |lentracy at gmail.com

--- Comment #1 from Salva Climent <jocliba at gmail.com> 2011-02-27 08:32:26 EST ---
Hi,

I’ve done a little bit of research… 

In [1] the attenuation is in db/km. According to [2] Thorp’s attenuation
formula in db/kyard is:

Fsq = f * f
alpha = 0.1*Fsq / (1 + Fsq) + 40*Fsq / (4100 + Fsq) + 2.75 * 10 ^-4*Fsq + 0.003

This formula takes care of the attenuation at very low frequencies (but it
doesn’t specify which range). 

In [3] another formula is used for freq below 1kHz:

alpha = Bs + 0.11*Fsq*K*(1+Fsq) + 0.011Fsq

where K is the coefficient which accounts for the regional variation of the
boron-related effects. Bs is the additions attenuation coefficient independent
of the frequency. Its value depend on the type of water mass and range from 0.2
* 10^-3 to 4.2* 10^-3. This time, attenuation is calculated in db/km.

And the next formula is used in [3] for freq. between 100Hz and 3kHz, also in
db/km:

alpha = 0.11*Fsq / (1 + Fsq) + 44*Fsq / (4100 + Fsq)

In [4], I think the original Thorp work, the following formula is shown (in
db/kyard):

alpha = 0.1*Fsq / (1 + Fsq) + 40*Fsq / (4100 + Fsq)

Maybe someone can take a look at [5]. I don’t have access to it and it seams to
be a review of all the work done by Thorp in this matter.

[1] Harris, A. F. and Zorzi, M. 2007. Modeling the underwater acoustic channel
in ns2.

[2] Urick, R. J.. Principles of underwater sound. 3rd edition

[3] Brekhovskikh L.M. and Lysanov Yu.P. Fundamentals of ocean acoustics. Second
Edition

[4] Thorp, W.H., 1967. Analytic Description of the Low-Frequency Attenuation
Coefficient.

[5] Thorp, W.H., Feb 1973. Attenuation of low frequency sound in the ocean

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