The Acoustic Doppler Current Profiler (ADCP) measures the speed
and direction of ocean currents using the principle of “Doppler
shift”. Anyone who has ever heard a train whistle is familiar
with the Doppler effect. When the train is traveling towards
you, the whistle’s pitch is higher. When it is moving away from
you, the pitch is lower. The change in pitch is proportional to
the speed of the train. The ADCP exploits the Doppler effect by
emitting a sequence of high frequency pulses of sound that
scatter off of moving particles in the water. Depending on
whether the particles are moving toward or away from the sound
source, the frequency, or pitch, of the return signal bounced
back to the ADCP is either higher or lower. Particles moving
away from the instrument produce a lower frequency return and
vice versa. Since the particles move at the same speed as the
water that carries them, the frequency shift is proportional to
the speed of the water, or current. The ADCP has 4 acoustic
transducers that emit and rec