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Large size bearing’s raceway waviness is a most common NVH issue that presenting in manufactured bearing. Unlike small or medium size bearing with its raceway been honed after grinding. Typically, for large size bearing’s raceway are not honed due to its size limitation, unless there are special requirements from customers. Hence, it will inevitably generate great number of waves on the raceway circumference, which lead to a significant source excitation to the system. Although great amount of experiments substantiated that bearing waviness will not affect bearing life. However, annoyance noise is the main reason that customer reject bearings for quality concern. Hence, at the early stage of identifying raceway waviness issue at customer site could prevent from economic loss. Generally, the energy level caused by large size bearing waviness could be distinctive.

The insertion loss of louvered terminations positioned at the end of a rectangular duct is determined using acoustic finite element analysis. Insertion loss was determined by taking the difference between the sound power with and without the louvers at the termination. Analyses were conducted in the plane wave regime and the acoustic source was anechoic eliminating any reflections from the source. The effect of different louver configurations on insertion loss was examined. Parameters investigated included louver length, angle, and spacing between louvers. Based on the analyses, equations were developed for the insertion loss of unlined louvers.