In this paper an experimental activity regarding the detection of noise produced by a high velocity train along a "almost" straight railway, and a semi-quantitative theoretical model which gives the shape of trains noise in that running conditions, are described. During this investigation the comparison between software predictions and experimental measurements was focused. At the present stage of our study we are starting with the theoretical reproduction of the time history of the phenomenon. In a previous paper we reported about the same goal referred to low velocity trains with very different operating conditions. So in this work we try to underline differences and similarities.The experimental measurements procedure is based on the detection of the sound level outside a building placed in an interesting position with respect to the rail line. It is some three hundred meters far and in a position from which one can observe more than three kilometres of railway. Measurements were performed by a first class Measuring System.
Noise produced by the transit of a train is affected by many variables: wheel-rail contact, engine, aerodynamic noise, random events, etc.. Some of these components, such as wheel-rail contact and aerodynamic noise are strongly dependent on high velocity, while other components, such as noise due to engines and auxiliary devices, are relevant in a low velocity regime, especially in proximity of a railway station, in the approaching and leaving phases.In this paper we describe both an experimental activity regarding the measurements of noise produced by low velocity trains and detected on a building façade, close to a railway station at night time, and a semi-quantitative theoretical model which gives the principal shapes of freight trains in various dynamical situations.At this stage of the study, we focus on different types of trains and of running conditions, evaluating their influence on the time history by means of comparisons between software predictions and experimental measurements. The experimental method chosen rely upon the simultaneous detection of the acoustic signals detected by two receivers placed some 30 meters apart and linked to the channels of a class 1 Measuring System.
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