It seems now widely conceded that Quiet Vehicles are actually too quiet for leaving out the crucial question of their sound signature. When considering the increasing volume of works in that domain, it looks obvious that a dedicated sound design approach for these new means of transport becomes fully relevant regarding security (for people around) or ergonomics (for people inside). For quite a long time, and among other labs, the Sound Perception and Design (SPD) team at Ircam has focused a part of its works on that topic which represents an emblematic framework to operate knowledge, methodologies or tools developed in the field of Sonic Interaction Design. The paper aims at presenting, first, an overview of recent scientific studies in that field together with a review of current legislations or standards that are – or tend to be – effective in several countries. In a second part, we will try to adress this issue in the light of several works achieved within SPD team, especially some parts of a long run collaboration with a french car manufacturer, but also more recent investigations that contribute to the general question : what is the best sound for a quiet vehicle ?