A study of vehicle and measurement NVH variability

A range of nominally identical automotive vehicles have been tested for NVH variability by exciting the engine mount with an impact hammer and measuring the responses at different points on the vehicle. Normalised standard deviations were calculated from the mobility, which fell well within the boundaries of previous comparable measurements. The measurement variability was determined by taking repeat measurements on a single vehicle, which were found to be very repeatable, varying by up to 2.9%. A function that uses the coherence to determine the random error was applied to the data to determine the variability due to the measurement taking process. This was compared with repeat measurements taken on a single vehicle and was shown to agree well with one another. A design of experiments has also been created that determines the effect of each variable such as the temperature and angle of impact on the overall vehicle to vehicle variability.