Ground vibration boom Ground vibration boom Ground vibration boom is a phenomenon of very large increase in ground vibrations generated by high-speed railway trains travelling at speeds higher than the velocity of Rayleigh surface waves in the supporting ground. This phenomenon, which is similar to a sonic boom from supersonic aircraft, was theoretically predicted in 1994. Its first experimental observation took place in 1997-1998 on the newly built high-speed railway line in Sweden (from Gothenburg to Malmo) for high-speed trains X 2000. At some locations along this line characterised by very soft ground (near Ledsgard) the Rayleigh wave velocity was as low as
Acoustic shock Acoustic shock Acoustic shock is the symptoms a person may experience after hearing an unexpected, loud sound. The loud sound, called an Acoustic Incident, can be caused by feedback oscillation, fax tones, or signalling tones. Telemarketers and call centre employees are thought to be most at risk. During the exposure, most people will experience discomfort and pain. After the exposure, some people might report shock, nausea and anxiety or depression. Headache, fatigue, hypersensitivity to loud noise and tinnitus may continue for days, weeks or indefinitely. It has not been established how such unrelated symptoms might be caused by an acoustic