Development of a time-domain Active Noise Equalizing (ANE) controller using a finite element model and real-time simulations

The acoustic signature of a ship is critical for detection and identification. Therefore, studying and controlling hydroacoustic signatures is increasingly important, especially in military applications where stealth is crucial. Frequency-domain ANE controllers are commonly used, because they can target specific frequencies effectively. Although, time-domain controllers provide fast and robust noise control, they are still underexplored. Here a time-domain ANE controller is being developed, using rapid control prototyping and a finite element (FE) model of a simplified ship hull section. To enable real-time simulation, the FE model is converted into a time-discrete linear-time-invariant-state-space model, using subspace methods. The controller combines Active Vibration Control with the FxLMS algorithm, modified by a signal processing algorithm to manage multi-tonal noise reduction and amplification. Validation occurs in a combined simulation, with noise reduction and amplification, tested under dynamic environmental conditions. Furthermore, the simulation results are validated experimentally. The controller is implemented and tested on a scaled model of a patrol boat (1:8) under laboratory conditions (airborne sound field). The measurement setup is similar to the FE model of the controller development. Results show that the time-domain controller is capable of reducing emissions of tonal frequencies in multi-tone excitation by up to 15 dB.