Periodic signal is abundant in ship radiated noise. Its detection is an important step towards active control of ship’s acoustic signature. Based on power spectrum analysis and DEMON analysis, an approach to detect line spectrum and modulation spectrum of ship radiated noise is proposed. Periodogram method is used for power spectrum estimation. The separation of line and continuous spectrum, false positive removal, and line spectrum merging are conducted to improve the quality of detected characteristic line spectrum. Via DEMON analysis, steady physical characteristics including propeller’s rotational speed and number of blades are obtained. Finally, the effectiveness of the approach is demonstrated by simulation results.

An approach to actively control the low frequency linear spectrum in vessel navigation noise is proposed. The approach relies on the introduction of a secondary noise-cancellation source which is fixed aboard and whose signal generation uses the estimated location knowledge of the receiver. Loss of underwater acoustic transmission is modeled and Monte Carlo simulations are conducted to analyze the noise-reduction effects under different location estimation errors. Simulation results show that bearing estimation error is the predominant factor affecting the radius of the effective noise-reduction region, while distance estimation error has considerable effect only when the perpendicular distance from the receiver to vessels course is quite small. Besides, when bearing estimation error is less than 1.2° and distance estimation error is less than 80%, satisfactory noise reduction region can be obtained using the approach.