This has the following background: Acoustics continues to gain more and more importance as a differentiating feature and characteristic with regard to customer satisfaction. Wind noise in particular, in addition to rolling noise and tyre road noise, continues to come to the fore inside the vehicle with the electrification of the powertrain. In order to be able to counter this even better, the microphone array system for wind noise measurements on vehicles was installed in the aeroacoustic vehicle wind tunnel at the beginning of 2019. In the meantime, it has proven itself excellently in customer measurements.
With this system it is possible to measure the outside noise simultaneously from the side and from above. Matthias Riegel from the Vehicle Acoustics and Vibration Department says: "This is a new, modern measurement system that significantly simplifies and accelerates the acquisition of aeroacoustic sources on the vehicle". The system also includes an interior ball array.
The system has two main advantages: "Sound mapping of almost the entire vehicle is now also possible in 3D, as is correlation of exterior and interior noise". The latter means that both the noise source generated by the vehicle body can be detected and the transmission path to the interior can be analyzed. In general, the new system should help to carry out "a faster and more effective development process in aeroacoustics development in the vehicle wind tunnel". This enables an efficient use of the cost-intensive, coveted wind tunnel time and offers the engineer extended possibilities in aeroacoustic vehicle development. Both mean a significant added value that fully benefits the customers of the wind tunnel.
The technical features are as follows:
Dimensions of the arrays allow the measurement of vehicles up to 5.5x2.3x2 m (length x width x height).
Side array: 144 microphones, ceiling array: 168 microphones, interior sphere array (56 microphones)
Dynamic range: 14.9 dB at 10 kHz
Spatial resolution: <0.46 m at 1 kHz
According to Riegel, the planning took a total of one and a half years, the installation and commissioning took place within 2 weeks. With regard to the use for research purposes, Riegel says: "Using the interior sphere array, the relevant sound sources can now be examined in detail and specifically minimized. The microphone array thus makes an important contribution to vehicle development".