Automotive Acoustics Conference 2023

Author: Frank Jung

News from the 7th International ATZ Conference on Vehicle Acoustics

BEVs Require New Acoustic and NVH Development

What innovations have been developed in the fields of acoustics management and NVH technology? Answers will be provided by acoustics experts discussing current trends at the Automotive Acoustics Conference 2023.

The rapidly advancing electrification of modern powertrains also requires a special effort for acoustic development. How these challenges can be met is one of the topics discussed at the Automotive Acoustics Conference on July 11-12, 2023 in Rüschlikon near Zurich (Switzerland). Around 200 participants from 19 nations experience presentations that were as exciting as they were interesting.

The importance of noise, vibration, harshness (NVH) for the perceived value of an automobile cannot be overstated. It is these parameters in particular that reflect the quality and thus ultimately the standard of quality for the end consumer of a vehicle. And the importance of NVH is increasing, especially in electrified vehicles, where the absence of engine combustion noise contributes to the much greater perception of all other interior and exterior sounds. To cope with this, developers are faced with the task, among others, of effectively reducing not only powertrain noise but also noise from many other components.

International Participation

For 50 years now, the Automotive Acoustics Conference has been an indispensable forum for this discussion, as the CEO of the host company Autoneum, Eelco Spoelder, pointed out in his welcome address. After the forced break due to Corona, it took place for the first time as a hybrid event with 200 participants in Zurich/Rüschlikon, both online and in person. Marc Ziegler, responsible editor of the ATZ-MTZ Group, welcomed all participants on behalf of the organizer ATZlive. More than worth mentioning is the fact that despite a possible digital participation, the need for a personal exchange with colleagues on site weighed so heavily that the trouble of even a very long journey was gladly accepted. Clearly, conference calls are no substitute for face-to-face discussions. This was documented by the many visitors from Japan - who also made up the largest foreign group - as well as China, Taiwan, South Korea, India and the USA.

Electromobility is picking up speed globally and is thus increasingly a defining moment of development with regard to NVH, Dr. Davide Caprioli of Autoneum emphasized in his opening remarks. In Germany, the number of registrations of vehicles with electric drives exceeded the one million mark for the first time at the end of 2022. Worldwide, the figure was around 26 million, which is over nine million vehicles more than in the previous year. The most rapid development was by far in China, followed by the USA and Germany.

BEV Vehicle Noise Model

Thus, it was no great surprise that the two very first contributions, the keynotes by Dr. Léon Gavric, Senior Fellow Engineering at Stellantis, and Dr. Charles Zhang, Chief Expert in NVH at the Chinese automotive manufacturer BYD, also dealt with electric drive issues.

Gavric presented a model of external noise generated by battery electric vehicles (BEVs) for urban driving conditions. The basic idea of the model is to use prescribed measurements for tire and vehicle pass-by noise. Such a vehicle noise model could be used for the traffic models used in environmental acoustics, he said. In this case, the model covers urban traffic conditions. "Noise pollution in many cities can cause serious and long-term damage to health, with the most important and preventable sources being traffic and industry. Motor vehicle traffic is the largest contributor to noise in most cities," Gavric said.

In China, alternative drive vehicles already reached a 25 % share of the automotive market in 2002. In this field, BYD is one of the main players with 1.86 million such vehicles sold in 2022. BYD also sees the environmental acoustic problem and identifies NVH as one of the main development areas, as Zhang outlined afterwards. Many efforts are therefore being made to continuously improve NVH, he said – it is an essential part of the development strategy for the new EV platform. Zhang focused on the question of how road noise can be reduced in electric vehicles. Here he explained the so-called CTB (Cell To Body) technology.

Sound Insulation with Absorber Bodies

Dr. Klaus Pfaffelhuber from Autoneum presented the project on the "Application of sound-absorbing near-field bodies to reduce tire-road noise", which he had developed in cooperation with Bernard Zobec, Johan Grébert, Michael Scheinhardt and Jan Horak. The solution consists of absorber bodies that are mounted in the transition area from the wheel arch lining to the underbody in front of and behind the wheels and face the sound source, consisting of the road and tires. Pfaffelhuber showed the results of a recent study on the exemplary implementation of such bodies and their effect on the exterior and interior noise of the vehicle. In a Mercedes EQS, near-field absorbers made of textile sound-absorbing underbody panels were installed in the transition area from the wheel arch lining to the underbody in front of and behind the wheels. The acoustic effect of such a concept on pass-by noise and interior noise was measured at the Mercedes test track in Immendingen.

Eric Sorber of Siemens Digital Industries Software in Belgium devoted his presentation to "Implementing a method for predicting virtual road noise using virtual vehicle assemblies." He presented component-based transfer path analysis, a method for predicting road noise using virtual prototypes assembled from test-based and CAE-based component models. The methodology used is that for characterizing components for structure-borne noise, which Sorber impressively explained using a real case study. This involves predicting the driving noise behavior of a virtual prototype and breaking it down into the contributions of the structure-borne noise paths, which are evaluated from objective and subjective points of view.

"Improving passenger car tire noise by damping body panels using resonant structural metamaterials" was the subject of the presentation by Dr. Saverio Tufano, NVH expert at Nissan. He concluded the first morning by explaining how 3D-printed resonant elements can be used to damp the vibrations of a body panel that radiates tire noise into the passenger compartment. The experiments were conducted on a complete vehicle and show a high potential for vibration reduction in the tuned "stop band," which is accompanied by an improvement in interior noise.

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