Crankshaft Rumble Noise Phenomenon: Experimental Characterization of Source Strength and Path Response

A series of system level experiments were conducted using 2 vehicles of identical design to measure, analyze and quantify crank rumble noise from the viewpoint of source strength and path dynamic response. One of the vehicles was known to produce relatively severe crank rumble response (noisy), while the second vehicle was almost free of the annoying response (quiet). Two specific operating conditions most susceptible to crank rumble noise were of interest: (1) no load snaps in neutral and (2) hard acceleration in second gear. For each condition, the vibration and sound pressure responses throughout the vehicle were obtained. The measured data was analyzed critically to determine frequency content and strength of rumble noise at each location. Calculations were also performed from the measured data to determine the modes of transmission and the relative contributions from air-borne and structure-borne paths.