Predicting complex rattle noise using the harmonic balance method and experimental validation on a rattle test rig

Rattle noise inside a passenger vehicle must be prevented for quality and comfort. Eliminating the unpleasant noise incurs high development and production costs for the vehicle manufacturer. Thus, a numerical method for predicting rattle noise in the early, virtual development phase is sought. This research presents a method to predict the non-smooth vibro-impact behavior of rattle noise-emitting structures. It focuses on the computation and experimental validation of the complex, multi-impact-per-period rattle noise on a rattle test rig. The computational method is based on non-linear theories and combines the Harmonic Balance Method with the Alternating Frequency/Time Domain Method. With a penalty formulation, it captures the root cause for rattle noise, i.e., repeated impulsive contact interaction. The simple single-impact-per-period rattle and the complex multi-impact-per-period rattle are measured on a rattle test rig, analyzed, and predicted numerically. While the computation of the single-impact-per-period rattle uses a single-harmonic forcing, the complex multi-impact-per-period rattle requires a multi-harmonic excitation to exhibit the acoustically important richness in higher harmonics. Moreover, a multi-harmonic excitation represents the actual excitation inside a vehicle better than a single-harmonic forcing. Finally, the findings imply that a multi-harmonic excitation is advantageous for predicting rattle noise inside a passenger vehicle.