Speaker
Description
The close-proximity (CPX) method according to ISO 11819-2 is increasingly applied to monitor and character-ize road surfaces. To better understand the physical mechanisms underlying CPX measurements and to enable predictions of CPX spectra, a hybrid simulation model called CPX simulator is developed. This contribution presents experimental and numerical investigations conducted during model development. First, an experi-mental approach to quantify the influence of the tire tread pattern on CPX spectra is introduced. The results re-veal that the tread pattern of the used standard reference test tire (SRTT) plays a decisive role, particularly for smooth pavements at low driving speeds. The horn effect of a loaded tire is simulated using 3D FDTD. The sim-ulations highlight the impact of the circumferential tire grooves and the acoustic impedance of the pavement on CPX spectra. The influence of the CPX trailer enclosure was examined through narrowband measurements using an artificial sound source. The observed distinct trailer influence at low frequencies can be well repro-duced with a modal sound field description. Finally, predictions with the CPX simulator are compared to CPX measurements performed in Switzerland on various pavement types at different driving speeds. The compari-sons confirm that the hybrid model accurately captures the combined influences of speed, pavement surface texture, and pavement impedance on spectral CPX levels.