Electric Vehicle Sound Quality 1999-01-1694

Environmental concerns as well as regulatory requirements are driving the development of alternative vehicle propulsion systems. Electric vehicles (EV's) are attractive because they emit no pollutants. In this paper, we examine the sound quality characteristics of wind and powertrain noise in electric vehicles. Sound quality is an important attribute of EV's, because the expectation is that they will be very quiet due to the absence of an internal combustion engine. As we show in this paper, the absence of engine noise is both a blessing and a curse for sound quality. For wind noise, the results show that electric and gasoline vehicles have equivalent wind noise loudness levels at all speeds. However, at lower speeds (50-60 mph), the EV is judged to have more wind noise even though the level was the same as the gasoline vehicle! The difference is that, in the EV, there is no engine noise to mask the wind noise. While EV's have no engine noise they do have powertrain noise, primarily from the planetary gears used in the transmission. During accelerations and decelerations, there is significant gear whine. If reduced to tolerable levels, this gear whine can provide a not unpleasant audible feedback as the throttle is manipulated. At idle, EV's make virtually no noise. Thus, any accessory noise (A/C, power steering pump, fan) will be quite prominent and may be annoying due to it's strong tonal quality. While electric vehicles will be relatively quiet, they still present significant sound quality challenges.