In the proximity of the meeting location, a vehicle based demonstration of a sound emitting device was in order to evaluate recognisability as well as impacts on interior noise. A Hybrid vehicle equipped with two speakers, one at each front and end of the vehicle, and two different sounds were shown.

Prior to the demonstration it was explained that the sounder fitted to the vehicles would not meet the proposed requirements from NHTSA. The signal fulfills all the basic requirements in terms of detectability and locatibility and at the same does not penetrate into the vehicle.

The sound of the AVAS fitted to the demo vehicle did not have the full spectrum as initially specified. However, it contains ten 1/3 octaves with distinct signal/noise ratio between 1 – 8 kHz. This along with the modulation is the reason why it is detectable despite its low SPL.

The chair asked to explain how the sound that was heard during the demonstration compared to the proposed requirement in the NPRM. CLEPA stated that is meets the intend of having content between <1kz to >5 kHz and at least 8 1/3 octave bands with a distinct signal/noise ratio so to give sufficient info for detectability and locatibility. With 4 of these bands fulfilling the requirements as described, it meets about 50% of the NPRM. The overall SPL is about 52dB. The second sound had much more tonal content with a very dominant signal at 1 of the 1/3 octave bands which lead to a penetration into the cabin. The overall SPL was about the same. ISO requested CLEPA do deliver to the group a more detailed analysis of the presented sounds. NFB supports ISO’s observation that the sounds as presented fulfilled the intention in terms of detectability. OICA questioned if the SPL during forward driving was the same as during reverse. The reason behind this question is the fact that on trucks other than on passenger cars, a speaker would have to be mounted very near to the windscreen and can’t be so that there is a much higher risk of driver annoyance. CLEPA confirmed that the SPL measured at the speakers is identical, but due to the lower masking effect of the rear speaker, the intrusion of signal coming from the rear speaker into the cabin was much higher.

On request from NHTSA, CLEPA stated that there is noise known reason for the hardware as used on the vehicle cannot meet the specification as proposed by NHTSA. However this remains to be practically proven. Japan mentioned that the first sound was not in line with the requirements from the Japanese guideline as a continuous sound is required, whereas the demonstrated sound contained modulation. ISO claimed that the term of ‘continuous’ may need a concrete definition as some may see the modulation from the first as continuous while other what interpret continuous much stricter. NHTSA mentioned that modulation may be desirable as it may lead to improved detectability.