Acoustic Doppler is a technology that uses sound waves to measure the speed and direction of moving objects, typically in water. It works by emitting sound pulses and analyzing the frequency changes of the echoes that bounce back from moving particles or surfaces. This frequency shift, known as the Doppler effect, allows researchers to calculate the velocity of currents or fish in rivers, lakes, and oceans. This method is widely used in various fields, including oceanography, hydrology, and fisheries management. Acoustic Doppler devices, such as ADCPs (Acoustic Doppler Current Profilers), provide valuable data for understanding water flow patterns and aquatic life behavior, contributing to environmental monitoring and resource management.