# Sonar calculator algorithms

This page details the algorithms used in Sonar Calculator.

Where:

*c* = speed of sound (m/s),

α = absorption coefficient (dB/m)

*T* = temperature (°C)

*S* = salinity (ppt)

*D* = depth (m)

f = frequency (kHz)

### Speed of sound in salt water (Mackenzie, 1981)

where -2 < T < 30

25 < S < 40

0 < D < 8000

### Speed of sound in salt water (Leroy, 1969)

where -2 < T < 23

30 < S < 40

0 < D < 500

### Speed of sound in fresh water (Del Grosso and Mader, 1972)

where 0 < T < 95

D = 0

### Absorption coefficient (Francois & Garrison, 1982)

where:

This algorithm applies to all oceanic conditions and 200 Hz < f < 1 MHz.

**Note**: The Francois & Garrison (1982) algorithm calculates the absorption coefficient in units of dB/km. Echoview displays the calculated absorption coefficient units in dB/m as recommended by MacLennan et al (2002).

#### See also

About Sonar Calculator

Sound speed references