Search Results

Vehicle NVH (Noise Vibration & Harshness) is of continued concern to customers in this increasingly competitive market and driveline NVH performance is a key factor in overall vehicle quality. A typical way to increase this quality is the use of axle end of line test stands that utilize NVH signal analysis methods to offer pass/fail criteria. In the manufacturing environment there are high costs associated with axle assemblies that are rejected due to the amount of time for NVH analysis to determine root cause for the failure. Of more interest to both product development and manufacturing activities is the ability to understand the root cause of the failures from the axle end of line test stand. This information can improve the manufacturing process by eliminating errors, streamlining re-build activities, aiding in product design improvements, and in turn reducing cost.

The blind community is concerned that vehicles are becoming too quiet and unsafe for pedestrians1. With vehicle manufacturers successfully working to develop quieter vehicles and the emergence of a new class of quiet hybrid and electric vehicles, this concern from the blind community will continue to increase. The basis of this concern is that a blind person uses acoustic cues to determine the location and speed of vehicles to avoid dangerous situations. To begin understanding this concern a jury study at the National Federation of the Blind California conference was performed. A combustion engine vehicle was converted to an electric vehicle and speakers were attached at each corner. Blind volunteers from the conference participated in the study where the vehicle was driven past them three times under different conditions. The subject raised their hand when they heard the vehicle and the distances from the subject were noted.

Shock absorber transient noise, often referred to as “chuckle” or “loose lumber”, has been a vehicle level noise and vibration concern for many years. The noise often occurs with lightly damped shock tuning under small road inputs at low speed. This transient type noise is of particular concern to the operator because it can sound like mechanical looseness in the chassis. This noise concern is generally addressed late in the design cycle and the options of a fix are limited to a change in damper tuning or added mass. A need for a wider design envelope exists to address this concern which must include noise paths into the structure and body sensitivity. The study documented in this paper walks through the process of acquiring this noise on the road and reproducing it in the lab on a 4-post hydraulic test rig.