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On existing NS trains (the Intercity trains and the Double-Decker slow trains) the current cast-iron brake blocks create small flat areas on the running surface of the wheels. The wheels become less round and this causes them to vibrate. This vibration produces noise. Alternative brake blocks are being tested to prevent this train noise. These brake blocks provide a reduction in noise of about 7 decibels.
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In July 2007, the sound of a double-decker train, consisting entirely of silenced rolling stock, was measured on the ProRail test facility at Susteren. The rails on this stretch of track had recently been acoustically planed and this ensured a very quiet train passage. Watch and listen to the following film recording.
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The NS service schedule has included a number of intercity vehicles (ICRm) with silent brake blocks since halfway through May 2006. This test will take around a year and must, amongst other things, provide information on noise reduction and the durability of the brake blocks. A second test was started up in March 2007 with a number of modified double decker stopping train vehicles (DDM1) (with LL brake blocks) An investigation was also started up in March 2007 into the possibility of using LL blocks on older single-decker stopping train stock (Mat'64). A mobile sound measurement unit was specially set up for this purpose along the track between Weesp and Almere.
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The SileNS noise measurement notes appear below. The underlying TNO and dBvision reports are accessible through the Rail Noise Knowledge Centre documentation system.
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