Sir - May I draw your attention to an error that crept into my recent article about the Lok Ma Chau Spur Line in Hong Kong (RG 2.06 p74).
In the section on track design, reference is made to floating slab track laid at Lok Ma Chau station and in the tunnel at the site of the future Kwu Tung station. The article states that this has a resonant frequency of 12 to 14 Hz with low-stiffness resilient bonded base plates of 15 to 25 kN/mm, giving a noise attenuation of 10 dB in the 200 to 500 Hz spectrum. In fact the noise attenuation for floating slab track is 20 dB in the 200 to 500 Hz spectrum.
The figure of 10 dB quoted in the following paragraph for the noise attenuation of low-vibration track is correct.
Joey Koo Kwok Hung
Permanent Way Manager
Kowloon-Canton Railway Corp