Adaptive control method for low-frequency line spectrum noise based on normal intensity

A noise adaptive control method based on the normal acoustic energy flux of underwater structures is proposed to control low-frequency radiation noise in the far-field of underwater structures. The method utilizes the normal acoustic energy flux in the near-field of the structure as the control physical quantity, and adaptively adjusts the output of the secondary sound source using an active control system to suppress the energy propagation in the normal direction of the structure, thereby achieving reduction of low-frequency radiation noise in the far-field. The experimental results, based on a cylindrical shell model, indicate that within the frequency range of 1000 Hz to 3000 Hz, the energy flux control method, as opposed to the traditional active control method using near-field sound pressure as the primary control parameter, can achieve noise reduction in the azimuthal direction in the far-field area from 52.8% to 76.3%, while ensuring that the total radiated acoustic power remains unchanged. Furthermore, as the frequency decreases, the noise reduction range becomes wider.