The OICA database contains 97 vehicles in the meanwhile and will increase in future. It
consists of a standardized data input sheet for all relevant data in terms of technical data of
the respective vehicles as well as for sound emissions including ECE R51 pass-by noise. For
QRTV several conditions are recorded:
• Stationary with the intention to drive forward
• Stationary with the intention to drive reward
• 10km/h
• 20km/h
• 30 km/h
• 4 runs
• Stationary
  o Minimum
  o Maximum
  o Average over 10 seconds
  o 5 microphone positions
  o semi-circle around front and rear end of vehicle : left /right/center front /45 degrees
• Pass by
  o Maximum at entry into test track
  o Maximum at height of micro

Maximum SPL and frequency analysis is measured.

Also listening files are recorded; however we have not yet determined a common format.

Therefore this data is not widely distributed. Also interior sounds are recorded to get a picture of the effect of exterior sounds on the passenger compartment.

A sample is played of a vehicle that is equipped with a sounder that meets the proposed NHTSA requirements. The vehicle is prepared with the same insulation measures as applied to vehicles of the same types but with different powertrains. The sound sample shows that the interior noise increases by 3 dB(A). It is difficult to further improve the insulation measures. A sound coming from outside must not necessarily be completely suppressed, but it must be acceptable to the customer.

A pleasant sound composed of harmonics is potentially better accepted. One can imagine the requirements for 8 frequency bands as a minimum requirement with the possibility for the OEM to add further sound components. The 8 prescribed frequency bands must however have a lower minimum level. This would allow the creation of a sound well recognizable from exterior, but at a low interior SPL with an acceptable quality for the passengers.