Quantitative prediction of rattle noise: An experimentally validated approach using the harmonic balance method

Rattle noise in a car's interior must be avoided to prevent customer complaints. Virtually predicting such disturbing sounds without expensive prototyping has become more important in recent years to reduce development costs. For this reason, methods for simulating the acoustic behavior of rattling systems are gaining attention. This research validates the harmonic balance method for a quantitative prediction of rattle noise. For this purpose, a test rig is developed showing representative rattling and non-rattling configurations. The test rig consists of an oscillating beam-like structure with a lumped mass at its tip. When amplitudes are large enough, the beam serves as an impulsive excitation of a plastic plate. The nonlinear dynamic system response is measured using a 3D scanning laser Doppler vibrometer and the harmonic balance method is used to calculate the system's response, which predicts the first and higher order harmonics with high degree of accuracy. Furthermore, measurements and simulations show that solutions for the system's response are not necessarily unique for all predefined harmonic excitation frequencies. Finally, a motivation is given for why higher harmonics have to be taken into account to adequately predict the acoustic behavior.