range2tl

Compute underwater sound transmission loss from range

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Syntax

tl = range2tl(rng,freq,depth)

Description

tl = range2tl(rng,freq,depth) returns the transmission loss, tl, for a sound wave of frequency freq arriving from a source at distance rng. The channel depth is depth. The transmission loss is due to geometrical spreading and frequency-dependent absorption. This function is the inverse of tl2range.

example

Examples

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Open Live Script

Find the transmission loss (in dB) for a sonar operating at 2 kHz in a channel that is 200 m deep. The sound path is 1000.0 m long.

rng = 1000.0;
freq = 2000.0;
depth = 200;
tl = range2tl(rng,freq,depth)
tl = 
50.1261

Input Arguments

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Distance from sound source to receiver, specified as a positive scalar. Units are in meters.

Example: 10e3

Data Types: double

Frequency of sound, specified as a positive scalar. Units are in Hz.

Example: 1e3

Data Types: double

Channel depth, specified as a positive scalar. The transition depth from spherical to cylindrical spreading loss is one-half the channel depth. Units are in meters.

Example: 200

Data Types: double

Output Arguments

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Transmission loss, returned as a positive scalar. Units are in dB.

Data Types: double

Algorithms

  • Three sources of transmission loss are modeled in the underwater sound channel functions range2tl and tl2range.

    • Relaxation effects for boric acid and magnesium sulfate. Relaxation effects depend on seawater salinity (S). alkalinity (pH). and temperature (T). The model assumes constant seawater salinity of 35 ppt (parts per thousand), pH of 8, and water temperature of 10°C throughout the sound channel.

    • Shear and bulk viscosity of pure water.

    • Geometric spreading loss is depth-dependent. For ranges less than or equal to the transition depth, the transmission loss is due to spherical spreading. For ranges greater than the transition depth, the transmission loss it due to cylindrical spreading. The transition depth is one-half the channel depth specified by the depth argument.

  • The transmission loss model is valid for frequencies up to and including 2.0 MHz.

References

[1] Ainslie M. A. and J.G. McColm. "A simplified formula for viscous and chemical absorption in sea water." Journal of the Acoustical Society of America, Vol. 103, Number 3, 1998, pp. 1671--1672.

[2] Urick, Robert J. Principles of Underwater Sound, 3rd ed. Los Altos, CA:Peninsula Publishing, 1983.

Extended Capabilities

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Version History

Introduced in R2017b

See Also

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