Japan presented results from various examinations on the requirements for the sound quality of AVAS. The examination result in the following suggestions:

• Sound must be emitted from at least 2 1/3 octave bands
• The audible distance should be proportional to the overall sound level

Both suggested requirements have been verified with various forms of testing including lab and jury testing.

The mentioned overall level shall be determined as a function of the vehicle stopping distance. However the required SPL to fulfill that target is not yet decided at the moment and needs further investigation.

1 kHz to 5 kHz is detectable for people with normal hearing; elderly people have difficulties with the higher frequencies.

OICA: on the first glance it appears as if it positive under environmental aspects to use as few energy as possible when producing a sound that is detectable because this reduces the overall SPL. But this has nothing to do with annoyance. Even a low SPL signal can be an issue for public. We must be careful not being too scientific when determining suitable frequencies, leaving aside the subjective aspect of public perception.

CLEPA: the frequency band from 1 kHz-5 kHz as identified by JAPAN is not only best for detectability but also for locatibility.

ISO: how precise do you need to define the content within one individual 1/3 octave band?

J: This question needs to be discussed in ISO.

OICA: In fact, looking at page 6 of the presentation, the shown curve may be interpreted to contain more than only 2 prominent frequencies, but 5 or even 6, depending on how narrow the definition of one frequency is taken. A clear definition is needed. This does also contain the opportunity to leave room for flexibility to the OEM as long as he designs sound outside of the defined requirements.