| sonar with synchronized transmission and reception, with transmit beams and receive beams fixed in space, but with no steering capability of the acoustic beams|
Note 1 to entry: Measurement of time of flight is inherent to all echo sounders. Measurement of amplitude is inherent to some echo sounders.
Note 2 to entry: The transmit beams and receive beams are often formed by the same transducer or transducer array, with acoustic fields whose spatial properties are essentially identical.
Note 3 to entry: An echo sounder is most commonly used to determine water depth.
Note 4 to entry: Note that the use in underwater acoustics of the words "transmit", "transmitter" and "transmission" to describe the process of sound radiation by a source is commonplace, but this deviates from the usage prescribed in IEV 702-02-05 where the words "emit", "emitter" and "emission" are preferred.