Railway curve squeal detection and tonal analysis

Railway curve squeal is a loud tonal noise generated by instabilities in the wheel-rail contact of railway vehicles while negotiating tight curves. The emitted noise is perceived as highly disturbing and contributes to noise problems in urban environments. Traditional monitoring of squeal occurrence involves analyzing train pass-by sound measurements. Such monitoring system is sensitive to high background noise which can pose a problem in urban environments with limited possibilities for suitable microphone placement. To overcome these issues, an alternative approach to detect curve squeal from rail vibration measurements is investigated. This comprises a simple and practical monitoring solution virtually unaffected by sound disturbances from the surroundings. Furthermore, this method can identify whether squeal noise occurs on the low or high rail. Field measurements involve a two-part analysis: 1) the development and validation of a method for detecting squealing events from rail vibrations, and 2) identifying tonal components from the measured signals. Results from the first part suggest that curve squeal can be detected from rail vibrations and the specific rail where squeal is generated can be identified. In the second part, specific frequency regions where squeal tonal components tend to emerge are recognized.