Marie-Agnès Pallas

Tram noise emission: Spectral analysis of the noise source contributions

In France we can assist to a wide development of tram networks for public transportation in main cities. At the same time arises questioning on the noise emission of trams and possible consequences for resident exposure. A French research project has been conducted for studying noise and vibration emission of trams : this paper concerns the description of the noise emission of passing‐by trams. A measurement campaign was achieved on the city of Nantes network, involving two kinds of trams with distinct technologies and equipment, and tested on two types of tracks having different platform surfaces. Acoustic measurement included both a 2D‐array for noise source identification and a microphone set for vertical directivity analysis. The dominant noise sources are mainly the bogie areas (powered bogies, unpowered bogies) and an extended noise source along the track and the lower part of the tram, all of them involving rolling noise. This paper focuses on the spectral description of the main sources. A paramet...

Identification of acoustic moving sources in the context of a road vehicle at pass-by: A numerical comparison

The problem of the identification of acoustic sources has been widely treated in static or quasi-static source contexts, more recently for moving sources, in a wide range of applications. Different methods have been developed in this endeavor. In the context of identification of sources from a passing-by vehicle, the beamforming method is a reference that has well-known limitations: a poor resolution at low frequencies causes difficulties to discriminate close sources or with too different levels, and the convolution of the point spread function with the source-signal makes it difficult to evaluate the level precisely. Deconvolution methods are used to overcome those limitations. Mostly developed in static contexts at the beginning, extensions to moving sources have been proposed in the transportation field, mainly in air transportation and underwater acoustics. In the present investigation, these methods are numerically tested with parameters fitted to the road vehicle context. Their performance is asses...

A German-French acoustic road pavement database: DEUFRABASE latest version

The aim of this database developed during two DEUFRAKO (German/French cooperation) projects is to provide a tool to predict in a large number of predefined situations, the impact of road pavements on Lden estimation for realistic configurations in terms of geometry, traffic composition and propagation effects. The method implemented is based on (i) the standardized light and heavy vehicles LAmax measured according to ISO pass-by method, (ii) on the relationship between this LAmax and the single vehicle LAeq calculated on a 1-hour time period, (iii) on the excess sound attenuation between two receivers, one located in the road vicinity (7.50 m-1.20 m) and the other in farfield and (iv), on an average daily traffic distribution. In 2008, a first version of the database was implemented and uploaded on the German partner’s website. More recently, the database structure has been redesigned to easily add new configurations of topography, traffic and pavements. New indicators, representative for instance of urba...

Identification of acoustic moving sources in the context of a road vehicle at pass-by

The problem of the acoustic sources identification has been widely treated in static or quasi-static source contexts, more recently for moving sources, in a wide range of applications. In the context of source identification from a passing-by vehicle, the beamforming method is a reference that has well-known limitations. Deconvolution methods are used to overcome them. Mostly developed in static contexts at the beginning, extensions to moving sources have been proposed in the transportation field, mainly in air transportation and underwater acoustics. In the present investigation, the method proposed by Fleury and Bulte is numerically tested with parameters fitted to the road vehicle context. Its performance is assessed at different speeds, source-to-array distances and with various additional noise levels, as well as its robustness regarding an error on some parameter inputs. Beamforming -- as the reference method -- and this moving source deconvolution method (here called MSA-PSF) are compared using per...