Korea carried out intensive research on road operation, monitoring and safety assessment of EV and typical drive pattern throughout the last 3 years. The appropriate SPL for AVAS can be determined by comparing human detection of ICEVs. In order to clarify the term ’Practical use’ as included in the GRB proposed guideline for AVAS sound, one must differ between the driving states deceleration, cruise and acceleration. On an ICEV, the SPL increases with acceleration. However so far testing for the development of the test method has only been done in cruise and it needs to be clarified if this is sufficient. The results already presented during the last meeting in Berlin showed data for cruise as well as for acceleration which supported the thesis that sound emission during acceleration is higher than during cruise. Between 2010 and 2012, during 1194 days in several cities, ‘Research of road operation monitoring on the EV’ was carried out. During these days, typical drive patterns were recorded and it turned out, that cruise condition is very rare. In summary the analysis of typical patterns revealed that:

  • Instantaneous acceleration or deceleration occurs continuously in actual road driving.
  • It is hard to see cruise drive patterns especially in low speed.
  • Also, it is not easy to maintain constant speed in low speed.

This leads to the conclusion that:

  • Many transient drive patterns are typical for real traffic situation.
  • Actually, it is hard to maintain constant speed within a low velocity.
  • We have to determine the reference driving condition either minimum level compared to ICEV or the real traffic sound level of ICEV.
  • The generated sound during cruise is close to minimum.
  • Therefore, the SPL should increase if we consider acceleration

ISO confirmed that the test procedure is designed to measure the minimum sound emission. During the development of the method is turned out, that it is difficult to reached repeatable constant acceleration at low speed and out of practical reasons it was decided test in cruise condition. Also ISO can support the finding that during acceleration, the emission is increased compared to the cruise emission at the same speed. The reason in the tyre torque effect. An AVAS only emitting the minimum of typical cruise condition at the respective vehicle speeds would simulate the pure vehicle or powertrain noise. An EV fitted with such an AVAS and under acceleration would however emit a higher noise as the noise coming from tyres would be produced and must be added to the AVAS emission. Therefore it is sufficient for the AVAS to produce cruise sound emission only. It must however be admitted that, an increase in engine speed and the associated increase of noise may occur prior to an increase of vehicle speed.