Experiences Tuning an Augmented Power Unit Sound System for Both Interior and Exterior of an Electric Car 2018-01-1489

A system for realistic augmentation of power unit sound has been applied to an electric car. Augmented interior sound has been shown to be a powerful enabler for the acceptance and appeal of electric cars. In some territories augmented exterior sound is a legal requirement, to provide a safe urban environment particularly for vision-impaired pedestrians.

An accelerometer located on the electric motor casing provides a live-streamed signal from the power unit that conveys authentic and genuine information. The sound’s level and frequency content are modulated by acceleration demand and vehicle speed signals respectively, thus tapping into the existing ‘language’ of car sound. Inside the car, this enriches the dynamic driving experience during spirited driving, while retaining acoustic comfort under cruising. The sound’s harmonic content can be enhanced and tuned to provide a variety of sonic timbres, reinforcing a wide range of brand and product images, although flexibility is limited to an extent due to the authentic sound source. Outside the car, a balance can be found between informing pedestrians effectively and avoiding environmental noise pollution.

A practical trial-and-error approach has been used to tune the gain map, filter parameters, and other controls. A set of simple tools was developed to support this, including input and output data logging, spectral analysis with order cursors, and simple slope and shape parameterization for the gain map. These tools can be used in the vehicle, enabling quick and interactive tuning of the system to meet interior and exterior sound requirements. Thus, a concise set of candidate sound schemes can be developed, to be presented to senior stake holders for selection.