An Echo Sounder is a type of SONAR (Sound Navigation and Ranging) device used to determine the depth of water by transmitting sound pulses into water.

1. The Working Principle of Echo Sounder &
Doppler effect in it.
An Echo Sounder is a type of SONAR (Sound Navigation and Ranging) device used
to determine the depth of water by transmitting sound pulses into water.
General Principle of an Echo Sounder
It works on the principle of transmitting sound waves from ship’s bottom and then
measuring the time taken for the echo to be returned from sea. If the velocity of
sound in water is known the time will be proportional to the distance travelled. The
time taken by the waves to travel to and from the seabed is measured and depth can
be determined, by the formula Distance=Velocity x Time/2
Detailed working principle:
1. Transducer: The echo sounder consists of a transducer, which is typically
mounted on the hull of a vessel below the waterline. The transducer converts
electrical energy into sound waves.

2. 2. Sound Waves: The transducer emits a pulse of sound waves, usually at a
specific frequency, into the water below the vessel. These sound waves travel
downward through the water column.
3. Reflection: When the sound waves encounter the seabed or any underwater
object, they are reflected toward the surface.
4. Return Signal: The transducer detects the returning sound waves, or
echoes, and measures the time it takes for them to travel from the transducer
to the seabed and back.
5. Depth Calculation: Using the known speed of sound in water and the time
taken for the sound waves to travel, the echo sounder calculates the depth of
the water beneath the vessel or the distance to the underwater object.
6. Display: The depth information is typically displayed on a digital or analog
screen on the vessel's bridge or navigation console. This display provides real-
time updates of the water depth, allowing the vessel operator to navigate
safely and avoid shallow areas or underwater hazards.

3. The Doppler effect in echo sounders:
The Doppler effect refers to the change in frequency or wavelength of a wave in
relation to an observer who is moving relative to the wave source. In the context of
an echo sounder, the Doppler effect can be used to determine the speed and direction
of underwater objects (like fish or submarines) by measuring the frequency shift of
the reflected sound waves.
Here's how it works:
Moving Object: When sound waves bounce off a moving object in the water,
such as a school of fish or a submarine, the frequency of the reflected sound waves
changes slightly due to the Doppler effect.
Frequency Shift: If the object is moving towards the echo sounder, the frequency
of the reflected sound waves increases. Conversely, if the object is moving away
from the sounder, the frequency decreases.
Speed and Direction: By analyzing the frequency shift of the reflected sound
waves, the echo sounder can determine the speed and direction of the moving object
relative to the sounder.
Overall, the echo sounder utilizes the principle of sound wave reflection to measure
depth, while the Doppler effect enables it to detect and analyze the movement of
underwater objects.
Reference:
1. https://cultofsea.com/bridge-equipment/echo-sounder/