Research on Phase Characteristics of Tonal Noise in Landing Gear

Landing gear noise accounts for a significant proportion of the total noise generated during aircraft takeoff and landing. The aerodynamic discrete noise of landing gear mainly consists of cylinder noise and cavity noise. Cylinder noise comes from cylinder vortex shedding, and cavity noise comes from wheel acoustic resonance. There have been many studies on the intensity and directionality of landing gear noise, but there is a lack of research on the phase characteristics of noise. This paper investigates the phase stability of acoustic resonance discrete noise in landing gear through acoustic experiments. For different inflow velocities and times, first-order and second-order modal noise have good phase stability, while second-order noise has better stability than first-order noise, while third-order modal noise does not have stability. The stability of the sound source itself can be inferred through the stability of the phase, which means that the sound generation process of the first and second mode noise is stable, the sound source characteristics are stable, and there is no interference in the propagation process. However, although the third order noise is stable, the sound generation process is unstable. At the same time, acoustic imaging technology was also used to identify the number and corresponding positions of three noise sources, further supporting the previous conclusion. This paper further reveals the differences between the discrete noises of landing gear, and the conclusions are helpful for the construction of landing gear acoustic prediction models and the design of landing gear noise reduction schemes.