Process for Optimizing Acoustic Vehicle Alert System (AVAS) for FMVSS-141 and Interior Sound Quality 2021-01-1121

The automotive industry is shifting towards the development of hybrid electric and electric vehicles. These vehicles primarily use electric motors for propulsion and can be significantly quieter to pedestrians than traditional ICE (internal combustion engine) vehicles. The NFB (National Federation of the Blind) and others highlighted a concern with these quiet vehicles related to pedestrian safety and the inability to use historical sound signatures to detect a moving vehicle. To address this concern, NHTSA created FMVSS 141, which identifies minimum external sound requirements for hybrid and electric vehicles during stationary conditions and in motion up to 30kph. [1] OEMs are now required to implement Acoustic Vehicle Alerting Systems (AVAS) that use external speakers to generate additional noise to meet the regulation. These noises are intended to raise the exterior sound level of the vehicles, while still attempting to maintain a quiet, pleasant experience for the passengers in the cabin.

The purpose of this paper is to outline the process used by an OEM to develop a sound which meets the FMVSS requirement with consideration towards a pleasant experience for the vehicle occupants. A systematic development process was created and will be discussed throughout this paper that includes speaker location, speaker component testing, vehicle dynamic test considerations, vehicle acoustic sensitivity evaluation, sound design including jury testing, and final sound tuning. By following a structured approach, the authors of this paper believe an AVAS system can be developed to produce an external sound that is the best balance between a robust passing of the regulation while maintaining a quiet and pleasant experience in the vehicle cabin.