What Is an Echo Sounder?
An echo sounder is a device that uses ultrasonic waves to measure depth. Many are attached to ships and used to measure the depth to the bottom of seas and rivers. Depth is measured from the time it takes for ultrasonic waves to be transmitted, reflected at the seabed, and returned.
In seawater, sound travels at about 1500m/s, so if it takes 2 seconds from transmission to reception, we know that the depth to the seabed is 1500m.
In recent years, multi-beam depth sounders using multiple ultrasonic beams have become mainstream, enabling depth sounding over a wide area at once.
Uses of Echo Sounders
Echo sounders are mainly used to measure the depth of the seafloor. Knowing the depth of the seafloor enables accurate charting, which is very important for ship operations and bay construction. Knowing information about the seafloor can lead to the utilization of these marine resources.
Principle of Echo Sounders
Echo sounders measure depth by utilizing the bounce of ultrasonic waves. Ultrasonic waves are emitted from a transmitter attached to a vessel toward the seafloor, and the reflected sound waves are received.
The specific method for calculating depth is “speed of sound x time between transmission and reception divided by 2. The speed of sound traveling through seawater is said to be about 1500 m/s, but it varies depending on seawater temperature and salinity. Accurate setting of the sound speed under the conditions to be examined is essential for accurate depth measurement.
In recent years, multibeam echo sounders, which use multiple ultrasonic beams, have become mainstream. Multibeam echo sounders use a fan-shaped acoustic beam called a cross-fan beam. Although fine corrections are required for vertically and obliquely transmitted sound waves, this technology enables a wide range of depth measurements and provides accurate information on the topography of the seafloor as an area.