Follow up of tasks assign during last meeting. In cooperation with OICA and SAE, ISO evaluates the findings from the first QRTV meeting. During the last meeting, issues had been identified in terms of Measurement and correction for 1/3 octave data, Measurement uncertainty and the use of minimum sound levels in 1/3 octaves for detection and recognition.

In addition to the handling of the known issues, also some new information is given on additional vehicles that are tested according to the requirements from the NPRM. Testing has been performed using the named requirements in order to show interior versus exterior and Indoor versus Outdoor noise data, results from jury testing, the application of the Loudness model and pitch shifting issues.

A comparison between overall sound level measurements revealed that while indoor measurements has advantages at stationary or low speed testing due to the lack of background noise, measurement at higher speed (20km/h and 30 km/h) is unsatisfactory due to the noise coming from tires interacting with the dynamometer rolls. For outdoor measurement, the findings are the other way round. Stationary/low speed is difficult to evaluate due to relatively high background noise, noise at higher speeds however can easily be measured. 1/3 octave bands can merely be measured outdoor as they are not stable but would need longer measurement periods. Indoor measurements at stationary and 10 km/h can be carried out with good result for precision and repeatability. At higher speeds, again there are issues arising from tire noise resulting in data that can so far not Cleary be identified.

The measurement of interior noise reveals a significant difference in noise levels between AVAS on and off up to >25dB.

The results from jury testing show good correlation between Lcrs OA sound level and the detection distance in the way that detection constantly increases with increasing vehicle speed.

Comparison between indoor and outdoor at 10km/h proves the same detectability of overall sound as well as for all 1/3 octave bands.

According to Professor Colin Novak, University of Windsor, Project Leader for ISO TC43/WG9 “Loudness”, the ‘Moore partial loudness model’ used by VOLPE is older version and needs to be updated. However the impact of that update is not clear and needs further evaluation. The impact in the 300-800 Hz band can be up to a 10 dB difference.

The model was intended for single frequency band analysis. Impact of multiple frequency bands needs further analysis.

The analysis of a simulated test with a small frequency band shifting with vehicles speed showed that this shift can be detected from comparing the overall noise levels at different speeds. This was to prove that frequency shifting can be objectively evaluated.

When comparing indoor with outdoor measurements results from a vehicle test however the concern with negative impact especially at higher speeds becomes obvious, outdoor even more than indoor. Clear recommendation therefore is to carry out simulated testing, either on the vehicle or at pure component level.

Forecast/Recommendations

Latest findings support a viable technical approach for measurement and analysis. SAE and ISO documents will be updated in short term to reflect editorial, clarification, and corrections noted in ISO/CD ballot comments (3-4 months for republished SAE J2889-1).

Inclusion of updated 1/3 octave measurement procedure and developed commencing motion procedure will take further time (9-12 Months for implementation into SAE and ISO).

Alternative pitch shift measurements need conceptual development and validation.

Choice of bands and levels might need to be reevaluated to better match required detectability without negative interior noise impact to customers. The conflict between the requested detectability of an approaching vehicle for road users and the potential annoyance of vehicle passengers can probably be solved by more accurately selecting frequency bands with the associated levels.

A test alternative for full vehicle outdoor measurements may need to be developed for more robust results. Pitch shifting reviewed to allow “Gear Shift” effect for improved detectability.

A clear guidance from the IWG on direction can reduce development time within ISO/SAE

Questions/remarks

OICA criticizes the low level of flexibility that the NPRM incorporates. An OEM needs the possibility to design a sound so to not only fulfill the required safety aspects but also customer expectations. Experience from interior sound design shows that while an average sedan driver would expect a high level of silence, sports car drivers would probably accept turbo whistling.

The basic concept of 1/3 octave bands needs to be overthought because it necessarily leads to sounds intruding into the vehicle and at the same time not being acceptable to the customer.

Other than sounds coming from the engine or even music, pure 1/3 octave risk to be rejected.

It is a political decision to allow pitch shifting to simulate gear changes or to purely simulate a vehicle speed increase.

Chair: do we already know what customers are ready to accept?

Canada: Marketing groups of OEMs best know about customer expectation and assumed acceptability.

OICA: As this is a new subject where we have very few experience, we can only guess based on experience we made with sounds from ICE. However it is obvious that sound is a very important attribute of a vehicle. We therefore strongly support the idea of having as much flexibility as possible, allowing us to reprogram a sound on vehicles in the fleet, once it turned out that a specific sound is rejected by the customer.