Composite organic brake blocks
Composite organic brake blocks can be devided based on friction coefficients:
LL - very low
L - low
K - high
KK - very high
At the time two technical solutions are available with type K or LL. The basic principle for a noise reduction at the source (wheel/rail - contact) is very simple: "Smooth wheels on smooth rails". With the use of composite brake blocks in combination with smooth rails the pass-by (rolling) noise is reduced by approximately 10 dB (A), which means a halving of the felt noise.
With K blocks a proven and fully homologated technology is available for new wagons - but not economically feasible for retrofitting due to high effort and costs. Since homologation of LL brake blocks a rotrofitting of the existing fleet can be done.
Composite organic brake blocks can be mounted on locomotives, passenger coaches, freight wagons and metros. The blocks reduces rolling noise and also brake noise. Composite brake blocks with added rubber content produces the lowest peak noise levels. Other types of LL blocks do not prevetn squeal, but still results in lower noise levels compared to conventiona cast-iron block brakes.