Alternator Whining Noise-A Sound Quality Concern in Passenger Car 2011-26-0018

Quality of the sound is one of the major parameter for the occupants comfort. The vehicle noise can be broadly classified into airborne and structure borne noise contributed by numerous aggregates present in vehicle. Among different vehicle aggregates the alternator, which is an important component in vehicle electrical architecture, can be considered as a major source of airborne noise. Generally, the alternator noise is combination of mechanical, aerodynamic, and electromagnetic sources. The ratio of these sources in the overall noise varies with speed and loading pattern. The mechanical and aerodynamic noise normally depends on speed while the electromagnetic noise variation is load dependent. Alternator whining is an irritant perception of the sound quality due to electromagnetic noise. When the alternator is loaded with electrical loads (like head lamp, tail lamp, wiper and HVAC) the sound level increases further.

This paper describes the systematic approach of problem definition, root cause analysis and measures to improve the sound quality of whining. The root cause analysis covers the electrical or mechanical disconnection of alternator and effect of belt tension variation on whining noise. The effect of loading pattern on the alternator whine was also studied. The paper also covers the solutions tried out and improvements recommended for the implementation