The new Aeroacoustics and Electric Drive Center (AEC) has started operations at the BMW Group’s Research and Innovation Center (FIZ) in Munich. After forty years, the old aeroacoustic wind tunnel is being replaced with this new facility update.
The new building consists of two halves. One half hosts the workshop, testing, measurement equipment and a prototype line for high-voltage batteries and inverters. The other is the technically and structurally unique wind tunnel – 100m, with a height of 45m and a width of 25m, which BMW claims is both the world’s largest vertical acoustic wind tunnel and the quietest.
Daniel Böttger, head of complete vehicle development at BMW AG, said, “Our focus is on meeting the premium standards of our vehicles. An important part of this is acoustics – particularly for quiet electric models. The new wind tunnel enables groundbreaking advances in aeroacoustics research.”
The new wind tunnel features a low background noise level (54.3dBA at 140 km/h), which is as low as a quiet conversation. This means the noises caused by headwind on the vehicle can be accurately measured in the new wind tunnel. With a nozzle cross-section of 25m² and a maximum wind speed of 250km/h, even the largest and most powerful vehicles such as the Rolls-Royce Phantom or the BMW X7 can be tested realistically. This is achieved through a blower capacity of 4.5MW and up to 100,000m³ of air per minute at 250km/h.
BMW says the wind tunnel is designed as an acoustic semi-free-field space. This means that apart from the sound-resistant floor, there are no sound reflections. This enables a realistic simulation of the road. The frequency range for semi-free-field conditions from 30Hz is unique for a vehicle wind tunnel and covers the entire audible spectrum.
The acoustic wind tunnel also hosts the latest measurement technology to drive vehicle development. A 216-microphone acoustic camera enables precise localization of background noises with an accuracy of less than one centimeter. In addition, the wind tunnel has a laser vibrometry system, used to measure the mechanical vibrations of the entire vehicle surface synchronously and without contact.
The wind tunnel is also ideally equipped to study wind and rolling noises, offering a high degree of flexibility when carrying out measurements. The wind rolling sound makes it possible to separate the phenomena of rolling and wind from each other (wind on/off, roll on/off). BMW says the new acoustic wind tunnel in Munich sets new standards in vehicle development and opens new opportunities for optimizing vehicle acoustics and aerodynamics.
The AEC constitutes two buildings; the special acoustic requirements being met with a special decoupling of the wind tunnel from the second ‘semi-detached house’ and the surrounding area. The entire building, from the 3m-thick floor slab to the façade, is sound-insulated against noises from the surrounding area.
The second ‘semi-detached house’ of AEC is home to workshops, testing and measurement stands and prototype lines. Here, the focus is more on electric mobility, such as building and testing prototypes of future high-voltage batteries for EVs. An area of 15,000m² is available for this purpose on several floors. Across a further area of 800m², inverters for future electric motors will be manufactured on a pilot line, under clean room conditions.