4. Acoustic sources

4.1 Source contribution as a function of speed

Environmental train noise results from the contribution of various noise sources, which can be classified into three categories: equipment noise, rolling noise and aerodynamic noise. The contributions of these different sources vary essentially with train speed.

When stationary and at low speeds up to around 60 km/h, train noise is mainly due to the noise of technical equipment. The noisiest of these are the ventilation systems used to cool traction motors, electrical converters, air-conditioning exchangers and so on. The second source is duct outlet noise (diesel engine intake and exhaust). The increased performance of rolling stock often leads to an increase in demand for electrical power, and therefore to a...