Author: Frank Jung

News from the Automotive Acoustics Conference 2025 – 8th International Conference on Vehicle Acoustics

The Importance of Vehicle Acoustics is Increasing

Acoustic engineers face challenging tasks due to the electrification of mobility. They'll be talking about the main trends and developments at the Automotive Acoustics Conference 2025. 

With the accelerated shift toward electrification of modern powertrain systems, acoustic development work is becoming increasingly important. How to master the new challenges in the field of NVH (noise, vibration, harshness) will be the focus of the Automotive Acoustics Conference, which will take place on July 8 and 9, 2025, in Constance, Germany, with around 180 experts from 18 countries participating. 150 of them will take advantage of the opportunity for intensive exchange on site at the Bodenseeforum, while 30 additional participants will join via online stream. A total of 28 interesting presentations will be available to choose from over the two days. Noise, vibration, and harshness have a significant influence on the perceived quality of a vehicle – a factor that is even more important in electric vehicles. This is because the absence of traditional engine noise means that other interior and exterior noises become more noticeable. The challenge for developers is therefore to optimize not only the powertrain but also other components in a targeted manner.

Davide Caprioli from Autoneum, scientific director of the conference, welcomed all attendees at the start and wished them two interesting and exciting days. For over 50 years, the Automotive Acoustics Conference has been a central forum for this discourse, as Eelco Spoelder, CEO of host Autoneum, emphasized in his opening speech, highlighting the importance of artificial intelligence and sustainability in the development of future vehicle models. For the second time, the conference was held in a hybrid format – on site and digitally. After many years in Rüschlikon, Switzerland, this year's venue was moved to Constance, marking a relocation from Lake Zurich to Lake Constance. Despite the option of participating online, many of the international guests traveled to the conference in person – a sign of the high value placed on direct exchange. Marc Ziegler, editor-in-chief of the ATZ-MTZ Group, welcomed all participants on behalf of the organizer ATZlive.

Development of the Volvo EX90

In Germany alone, the number of electric vehicles is rapidly approaching 2 million, and there are already an estimated 56 million electric cars on the road worldwide, with China accounting for the largest market share. The number of electric cars has risen by a third in 2024; at the end of 2023, the global fleet stood at just under 42 million vehicles. Once again, China led the growth, followed by the US and Germany.

The central importance of electric drive was directly reflected in the first keynote speech of the conference: Eskil Lindberg from Volvo described how, during the early concept phases of the Volvo EX90, the structural NVH characteristics were addressed in a controlled manner while at the same time creating the conditions for good driving dynamics and a high level of driving comfort. Low noise levels in the interior placed new demands on the NVH of the powertrain, for example in the form of high-frequency whistling noises. In his detailed presentation, he described the importance of body and chassis stiffness in ensuring vibration isolation between the body and chassis and in achieving a design that meets durability targets and strikes the right balance between NVH, ride comfort, steering, and handling.

Electrification of Commercial Vehicles: Ford Transit Custom

In the first presentation, Daniel Kierspel from Ford used the Ford Transit Custom as an example to illustrate the challenges involved in electrifying an existing commercial vehicle model. These challenges lie not only in integrating an ICE-HEV-BEV powertrain into a platform, but also in meeting a wide range of requirements for derivatives such as vans, double cab-in-vans, chassis cabs, buses, and the Nugget camper van. As part of the NVH targets, a driving simulator was integrated at Ford to enable the development team to simulate the realistic interior noise levels to be expected. This made it possible to diagnose potential fault conditions even for different road profiles and traffic situations. This method enables an improved target setting and coordination process. NVH performance evaluations are carried out using a customized model that utilizes data from various sources and regularly updates the input data as the program progresses. Thanks to the early model-based evaluations in conjunction with the driving simulator, physical prototype testing could ultimately begin at a high level of maturity. This proved to be extremely helpful in avoiding unpleasant surprises later on.

Noise Transmission Path Through the Trunk

After the first refreshment break, the next speaker was Kichang Jo from Hyundai, who gave a presentation entitled “Noise transmission path analysis and sound package optimization for BEVs using numerical simulation”. He explained how, in electric vehicles in particular, the amount of noise entering through the trunk increases, making sound insulation in this area increasingly important. However, since the rear of a vehicle has a complex structure and consists of various parts, it is not easy to identify the path through which noise is transmitted by vehicle testing and to find an efficient method for reducing interior noise. Therefore, Hyundai conducted a panel contribution analysis and a target cascade analysis of interior noise using the Statistical Energy Analysis (SEA) analysis model of the actual sound absorption performance of vehicles to identify the noise transmission path through the trunk of electric vehicles.

SEA Tool and NVH Analysis of Fully-trimmed Car Bodies

In their paper entitled "SEA hybrid p/Q correlated modelization process for vehicle transient 'on track' noise assessment", Jean-Baptiste Prunet and Johann Löwen from Stellantis explained that the SEA tool is traditionally used globally to provide a pre-dimensioned design for the acoustic package of the planned vehicle. However, since the insulation performance of the vehicle depends to a large extent on the contributions of smaller components, SEA does not seem to be able to provide a noise prediction for the interior, as SEA works with large assemblies and does not take the details of the vehicle into account. An operating model was therefore created that takes into account detailed component performance and realistic physical parameters. Since the issue of noise prediction at the passengers' ears remains within the scope of the designer's task and the purpose of creating a calculation model for the vehicle, Stellantis also conducted an analysis on the race track, including noise measurements at the noise sources.

Nicolas Driot from Hexagon devoted the last presentation of the first morning to the topic of "Recent advances in efficient fully-trimmed body NVH analysis". He began by presenting a methodology that correctly sequences the modal extraction process for the un-damped in-vacuum body and the rigid wall cavity model, as well as the calculation of the reduced trim impedance matrix (RIM). Care is taken to avoid unnecessary modal data recovery in order to speed up the process without compromising the numerical predictions. He also demonstrated a new air gap coupling condition for trim interfaces that enables a reduction in the size of finite element (FE) models for trim.

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