10th Challenge Bibendum
Brüel & Kjær was once again selected to perform the pass-by noise measurements at the 10th Michelin Challenge Bibendum, held this year in Rio de Janeiro in Brazil from 31 May to 3 June.
Challenge Bibendum is a forum where stakeholders interested in sustainable mobility meet to air their news and views on the political, economic, social and technical aspects of this, now more than ever, important topic. Both the public and private sectors are represented at the event, who meet to debate and gauge the issues.
Scientists, academics, engineers, car manufacturers and political players discussed their respective points of view at some thirty round tables, seminars, conferences and debates, that were widely covered by 450 journalists from the international press. At the opening ceremony, Brazilian President Lula declared sustainable mobility to be 'an enormous challenge that needs to be addressed immediately', before thanking Michel Rollier, Managing Partner of the Michelin Group, for choosing Latin America to host the event, which is the only one of its kind.
The Most Innovative Technologies and Vehicles
Manufacturers saw their most innovative vehicles put through their paces with technical tests on the road: electric passenger cars, hybrid vans, caterpillar buses… Some vehicles are already on the market; others, such as the Audi e-Tron, are still at the concept phase. Three rallies for each of three categories of vehicle were an opportunity to compete in a series of tests such as acceleration, maneuverability, CO2 emissions, fuel efficiency and, of course, environmental noise.
Brüel & Kjær’s first appearance at the event was in Paris in 2006. The organizers were impressed with the high-quality, speed and versatility of the pass-by system, able to deliver on-the-spot results of ISO standard measurements. This good impression has secured repeat invitations to subsequent events.
Unlike other Challenge Bibendum sites, Rio does not have a test track, so all pass-by measurements were made in public places – either on the street or in a car-park. This challenge in itself is not too great, but the task was made more interesting in that the two test sites involved were at opposite sides of the city. The drive time between the sites was only just shorter than the time between test sessions, but thanks to the pass-by system being fully integrated with drummed-cables, de-rig and set-up time is minimal.
Whines and Wheelspins
At the first site the test was to measure the pass-by noise of the vehicles during hard acceleration. From a standing start, vehicles were driven with wide-open-throttle (or the equivalent if an electric vehicle) until they passed the microphone pair stationed 20m away at the sides of the road. Type 7788 Pass-by Noise system was used to record the noise level at this point and immediately report it to the adjudicators - a clear benefit of the system since the throughput of vehicles was high and there was no time for post-processing.
Interestingly, there were two unexpected problems with this test strategy not usually present for standard pass-by tests. The first came from the electric cars, particularly the lightweight experimental ones. Their inherent noise was very low and all that could really be heard was the tire noise and the whine of the control electronics. At a green-field site this would not be a problem since the background noise would also be low and the the pass-by apparatus would be able to detect the vehicle noise. But because of the number of press photographers present happily clicking away at these new and exotic vehicles, a major part of the background noise at this first site was shutter-clicks with a level of the same order as the vehicle noise.
At the other end of the scale, some of the vehicles, like the Audi e-Tron, are so powerful that the noise 20m away from the standing start consisted mostly of wheelspin, drowning out the engine and exhaust noise. This gives a different meaning to tire noise.
At the second site, the test was more sedate, but technically more challenging. Here, vehicles were required to drive between two sets of microphone 'gates' spaced 200m apart. Again, the organiser's main requirement was immediate reporting of the pass-by noise results so they could compile the vehicle league tables as fast as possible. To facilitate this, two Type 7788 Pass-by Noise systems were set up. And remember, this had to be done in the short time available after the dash across the busy city.
Type 7788 is designed to be 'plug-and-play', which in this case it literally was. There was no time for fine tuning; unpack, erect, connect cables, and away you go, that was the order of the day. In fact, because of the short set up time, the pass-by operator elected to run the system from his car - turned into a mobile control room for the duration of the tests.
In total, without counting the many members of the public who attended the vehicle parade right in the centre of Rio, this 10th Challenge Bibendum attracted more than 6000 visitors, including 1500 Brazilian students, among whom may well have been future engineers who will go on to invent the clean, safe and connected car of tomorrow.
Bruel & Kjaer was honoured once again to participate in this event as the world leader in pass-by noise measurements, and to contribute to the development of advanced technologies for all of us to benefit from in the future. The next challenge Bibendum will be held in Berlin in 2011, where we fully expect to participate.