The Analysis and Mechanism of Engine ‘Intake Rumbling Noise’

This report relates to that kind of rumble generated in the passenger compartment during acceleration which is caused by intake noise. The rumble is a rough, unpleasant noise that comes into the passenger compartment during acceleration. This noise was reported to be caused by the resonant bending vibration of the crankshaft. However, the writer and associates found that intake noise from the air inlet could also cause the rumble in the passenger compartment as reported herein. By a modal analysis of the air column vibration generated in the inlet system parts and analysis of the air column vibration response to the force input from each cylinder, the writer and associates determined that the standing wave generated in the surge tank was the cause of the rumble.

By modifying the shapes of surge tank models for computer simulation that had been used in predicting booming noise, etc., it became possible to predict rumble level due to intake noise through calculation. Surge tank shapes which would reduce the rumble were studied using this simulation system.

Of the surge tank shapes which produced satisfactory simulation results, those which were considered to have a high level of practical usefulness were translated into prototypes. The prototypes were actually tested on cars to measure the rumble for confirmation.