In addition to far field measurements, a noise measuring trailer is used to investigate tire-road noises.

The inside of this trailer contains not only the measuring wheel, but also a number of microphones that record the noise of the investigated tire-road surface combinations directly at the point where they are created.

Compared to the methods of controlled and statistical pass-by, the system features significant advantages. The measurements can be performed very quickly, flow-along traffic has practically no effect on the results, and analyses are even possible at low driving speeds at which power train noises could interfere during statistical pass-by.