Investigation of the rolling noise sources on the tram of nantes with a microphone array
PALLAS ; LELONG
Type de document
COMMUNICATION AVEC ACTES INTERNATIONAL (ACTI)
PALLAS ; LELONG
Résumé / Abstract
As part of a research programme on the acoustic emissions of ground transportation, the tram of nantes has been investigated. In relation to the development of a noise model of the tram, microphone array measurements have been carried out. Rolling noise being the main noise source, the investigations aimed at pointing out noise differences between driving bogies and bearing bogies, as well as the influence of the track construction. The measurement and processing involved a horizontal line array with focussing and dedopplerisation. Acoustic cartographies for each pass-by of the tram in third-octave bands were drawn. Tram constant speeds ranged from 10 to 50 km/h. Some accelerating runs were also measured. Three types of track construction were tested : asp track (concrete bed with absorbing pads between the rails and the sleepers), floating slab on bridge, rails on ballast. The asp track appears to be the least noisy, with very little contribution from the rail/track except at higher speed. The measurements on the bridge show mainly the vibration of the whole structure, hiding even the pass-by of the wheels at lower frequencies. For the track on ballast, the contribution of the rail arises clearly and it may radiate even more as the tram is leaving than between bogies. The contribution of each noise source can be estimated.