For the reasons given in the Phase 1 report DOT HS 811 304] on this research, the Phase 2 work focused initially on the following idea. The lack of detectability of quieter cars could be remediated if they are fitted with synthetic sound generators that emulate the sound of typical ICEs and that future specifications for the vehicle sounds can be specified in terms of objectively measured parameters- namely, overall sound output as measured by the SAE J2889-1 procedure together with spectral distribution specifications for the minimum amount of sound level in one-third-octave bands. However, recognizability is a different matter.