Analysis and Mitigation of Parasitic Noise in Hydraulic Engine Mounts: Addressing Cavitation and Membrane Hitting

Hydraulic engine mounts are widely used in automotive applications to reduce vibration and noise transmission from the engine to the vehicle body by providing high damping at low frequencies and low damping/stiffness at higher frequencies. This is achieved by allowing sufficient clearance between components inside the hydro mount, activating hydraulic damping only with sufficient amplitude inputs. However, this inherently leads to the generation of Parasitic noises emanating from hydraulic engine mounts which significantly degrades the Noise, Vibration, and Harshness (NVH) performance of vehicles, presenting a considerable challenge in the automotive industry. This encompasses phenomena such as cavitation, arising from the formation and subsequent collapse of vapor bubbles within the working fluid due to localized pressure drops below the vapor pressure, and membrane hitting, resulting from the dynamic interaction between the fluid and the elastic membrane within the mount. Both noise sources are often difficult to trace back to the engine mount. This paper details a systematic approach for both detecting and mitigating these parasitic noise sources specifically in decoupled hydraulic mounts. This methodology is grounded in an investigative analysis conducted on a passenger car. The outcomes of this investigation offer practical strategies for pinpointing the fundamental causes of both cavitation and membrane hitting noise in hydraulic engine mounts and implementing effective solutions to improve overall vehicle NVH characteristics.