Patent ID: 7164621

Claim:
An underwater sounding apparatus comprising: a transducer unit having a plurality of vibrating elements for transmitting acoustic waves and receiving reflected echoes from which said underwater sounding apparatus derives received signals and obtains underwater information by analyzing the received signals; and a noise suppressor for removing propeller noise, said noise suppressor including: a reference signal generator for outputting as a reference signal of the propeller noise a reference received signal which is the received signal derived from one of said vibrating elements having a principal acoustic axis oriented approximately in a propeller direction or a reference beam signal having a principal acoustic-axis oriented in the propeller direction, the reference beam signal being produced from some of said multiple vibrating elements; a noise compensating signal generator for outputting noise compensating signals obtained by adjusting the reference signal using adjustment factors individually defined for the received signals or for receiving beam signals produced from some of the multiple received signals; and a signal synthesizer for removing the propeller noise from the individual received signals or from the individual receiving beam signals by synthesizing each of the received signals or each of the receiving beam signals with the pertinent one of the noise compensating signals.