Experimental research into active control of low-frequency line spectral disturbances in liquid-filled pipe

Noise radiation through the liquid-filled pipe system is the focus of noise control in the pipe systems of ships, while low-frequency line spectral disturbances with high energy need to be further suppressed. An Active Noise Control (ANC) system adapted to liquid-filled pipes is designed to attenuate low-frequency line spectral disturbances. This system is made up of the secondary source, controller, power amplifier, sensor etc. The system uses a frequency tracking algorithm to estimate the frequencies of noise, and a complex LMS algorithm to design the controller. A pump water circulation pipe system is implemented to validate the control system's performance in noise reduction through experiments. Active control experiments on noise sources with fixed frequency, sweeping frequency and multi-frequency are carried out respectively. The results show that the control system can track frequencies automatically, and effectively reduce the noise radiating from the pipe in cases of fixed frequency, sweeping frequency and multi-frequency. The ANC system can achieve noise attenuation of over 8 dB at multi-frequencies in liquid-filled pipes, and has good robustness. This provides a possible solution for the noise control of low-frequency line spectral disturbances in the pipe systems of ships.