Noise & vibration


Sona’s Beam Retarder, or silent brake, uses a cast composite metal bolted to the brake beam to reduce noise from friction as wagons pass the system.


of barriers. Maffei’s 2013 study into the impact of the barriers, published in the Science of the Total Environment journal, found that people living behind a noise barrier quickly forget the previous noise levels and became more dissatisfied with the loss of a view.


The high-pitch squeal often emitted by retarders has encouraged some manufacturers to explore alternatives.


Transparent barriers are now available that retain views but the arguments against their installation have resulted in an effort to reduce noise levels directly from the source. This is consistent with schemes


already underway to reduce rolling stock noise. For instance the UIC’s recently concluded Eurotrain project is


Without Bremex Annsys “basic” system


Sona, Germany, which was recently acquired by Siemens, has incorporated a noise abatement solution into its Beam Retarder TW-F for two rails and TW-E for single rail solutions which have been trialled at German Rail’s (DB) hump yard in Nuremberg. Sona’s system uses a cast composite metal developed by Micke Brühmann, Germany, a manufacturer of sinter metal friction materials. These are bolted to the brake beam on the system’s five force application units with a damping plate used to separate these


investigating the use of LL-block brakes, or silent brakes, which while replacing the brake blocks avoid a complete replacement of a wagon’s braking system. The UIC hopes that the success of the trial will result in a programme to retrofit Europe’s entire fleet of 600,000 wagons with the low- noise brakes.


While these measures will improve conventional braking, it will not affect noise at hump yards. Most hump yards use retarders to regulate the speed of wagons after they leave the hump. However, the high-pitch squeal often emitted by these devices has encouraged some manufacturers and operators to explore alternatives. The source of this noise is the contact between the steel brake beams of the retarder and the wheels as they pass. The retarder manufacturing business of


With Bremex Annsys “basic” system


segments from the brake beam. Trials conducted in Nuremberg have shown that the system


reduces friction noise by up to 20dB with replacement and reconditioning of individual pads scheduled for between 5 and 7 million axle passes.


Radically different


A radically different solution developed specifically for hump yards by Elpa, Slovenia, is the anti-noise system Bremex Annsys Basic which tests have shown is capable of eliminating high frequency braking noise of 130dB by 99%.


10 9 8 7 6 5 4 3 2 1 0


55 66 69 72 75 78 81 84 87 90 93 96 99 102 105 108 111 114 117 120 123 126 129 Distribution dB(A)


Figure 1: noise emissions at German Rail’s Nuremberg hump yard have clearly reduced following the introduction of Elpa’s Bremex Annsys system.


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The system is suitable for all types of brakes and is applied adjacent to the track before the wagon passes through the retarder. The system works by applying an environmentally-friendly abrasive material to the wagon wheel flank in contact with the rail brake as the wagon passes the applicator. Applying the material directly onto the wheel creates an intermediate layer of material which is thermally decomposed during the braking process but without impacting the properties of braking. During the process the released kinetic energy is converted into heat and not sound, thereby reducing the braking noise at its source. Figure 1 represents noise events measured before and after installation of the system. However, because other noises are present which reach 90dB or more, these noises limit the measured common effect of this system by up to 30dB.


The system is also in use at DB’s hump yard in Nuremberg, where the results in testing phase between 2009 and 2011 led to a full rollout of the system. IRJ


IRJ June 2013


Frequency %


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