Analysis of the Causes of Inlet Noise in High-Temperature-Resistant Axial Flow Fans

Analysis of the Causes of Inlet Noise in High-Temperature-Resistant Axial Flow Fans

The intake noise from high-temperature-resistant axial flow fans can sometimes be very loud, but many people do not understand the causes of this noise and consider it normal. However, because they work in such an environment for long periods, they remain unaware of the dangers around them, putting their health at risk. Therefore, it is necessary to investigate the reasons behind this. Among the factors affecting intake noise, on the one hand, the velocity or pressure excitation at the acoustic inlet of the intake system serves as the excitation source causing forced vibration of the air column, along with the spectral characteristics of the excitation function. On the other hand, the natural vibration frequency characteristics or frequency response characteristics of the air column within the intake duct system also influence the nature of the intake noise. Typically, the resonant response of the air column is the primary cause of the peaks in the intake noise spectrum. The third factor contributing to intake noise in high-temperature-resistant axial fans is the acoustic impedance characteristics at the sound outlet. The sound outlet is equivalent to a circular piston with a diameter of 2r. When it vibrates and emits sound waves, it exhibits an acoustic impedance response to the air load. The acoustic impedance of the load is a function of frequency and consists of acoustic resistance and acoustic reactance. High-frequency sound from high-temperature-resistant axial fans is characterized by plane wave propagation and strong directivity. Low-frequency sound, if emitted from the outer side of the nozzle, exhibits low directivity and is prone to diffraction.