Influence of the near field of secondary source and the elasticity of pipe wall on active noise control performance of liquid-filled pipe

The numerical models of liquid-filled straight pipe system with active silencers are established. The influence of the near field of secondary source in active silencers and the elasticity of pipe wall on active noise control performance under sound excitation is analyzed. The results show that the near field of secondary source is non-uniform, and the active control effect of some frequencies is poor or even the sound pressure level will increase when the error points are located in this region. The noise reduction can be increased by more than 10 dB when the error points are in the region of uniform sound field. The noise reduction of most frequencies can be increased by more than 5 dB by increasing the number of error points. The coupling between secondary source and pipe wall is strong because of the elasticity of pipe wall. Asymmetrically distributed secondary sources tend to excite the pipe wall vibration, which causes the troughs of control effect. The symmetrically distributed secondary sources can significantly improve the control effect. Increasing the number of secondary sources can improve the active-passive hybrid control effect of the system. However, it makes the sound field in the pipe more complex, and the active silencing effect of the models with multiple secondary sources decreases with increasing frequency.