tl2range

Compute range from underwater transmission loss

Syntax

rng = tl2range(tl,freq,depth)

Description

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

Examples

Estimate Range from Transmission Loss

Find the distance traveled by a sound wave with a transmission loss of 50 dB. The sonar operates at 2 kHz in a channel 200 m deep.

tl = 50.0;
freq = 2000.0;
depth = 200.0;
rng = tl2range(tl,freq,depth)

rng = 
972.1666

Input Arguments

tl — Transmission loss from source to receiver

positive scalar

Transmission loss from source to receiver, specified as a positive scalar. Units are in dB.

Data Types: double

freq — Frequency of sound

positive scalar less than or equal to 2 MHz

Frequency of sound, specified as a positive scalar less than or equal to 2 MHz. Units are in Hz.

Example: 1e3

Data Types: double

depth — Sound channel depth

positive scalar

Sound 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

rng — Distance from source to receiver

positive scalar

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

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. Peninsula Publishing, Los Altos, CA, 1983.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Does not support variable-size inputs.

Version History

Introduced in R2017b