High-speed train systems are generally quieter than conventional passenger and freight rail
systems for two main reasons:
(1) they are powered by an electric propul
sion system and not a diesel engine, which
generates higher passby noise; and
(2) HST system requires trackwork that is grade-separated, eliminating at-grade
crossings where other railroad trains are required to sound bells at the crossings and
warning horns starting at ¼ mile before they reach the crossings.
The total noise generated by a high-speed train
passby consists of the electric propulsion
system, wheel/rail interactions, and aerodynamic sound produced from airflow moving past the
train. At speeds of 160 miles per hour (mph)
or less the propulsion system and wheel/rail
interactions are the predominant sources of
sound. At speeds above 160 mph the aerodynamic
sound becomes the predominant source.