Low-frequency Noise Reduction Mechanism and Acoustic Characteristics of the Dipole Surface Source Structure

PurposeTo mitigate the low-frequency noise generated by vibrational equipment during operation, this paper introduces a synthetic sound source structure called the dipole surface source, leveraging the noise reduction properties of the longitudinal quadrupole source.MethodsInitially, the low-frequency noise reduction properties of the longitudinal quadrupole source were analyzed theoretically. Building on this foundation, the dipole surface source structure was developed. Subsequently, a theoretical model called the concentric circular piston source, comprising a primary sound source (G1) and a secondary sound source (G2), was established and simulated in COMSOL. Finally, the impact of various vibration parameters and errors on noise reduction effectiveness was comprehensively investigated through theoretical analysis and simulation studies.Results and ConclusionsInitially, the study examined the effect of vibration frequency (f) on noise reduction effectiveness, revealing that the dipole surface source structure performs significantly well in the low-frequency range. Subsequently, the effect of the amplitude ratio (alpha) and area ratio (beta) between G1 and G2 on noise reduction effectiveness was also analyzed, with optimal results achieved when alpha beta = 1. Additionally, the effects of frequency error (Delta f) and phase error (Delta psi) on noise reduction were investigated, showing that both factors negatively affect noise reduction effectiveness, with Delta f potentially inducing beat vibrations. From this analysis, it can be inferred that for any arbitrarily shaped low-frequency noise source, optimal noise reduction can be achieved by adding secondary sound sources to form a composite structure based on longitudinal quadrupole sources. This innovative approach offers a new perspective on low-frequency noise reduction.