Certain types of alcohol, riding in a car or anything that "sways", roller coasters, ferris wheels, or tilt-a-wheels, altitude change, are all causes too.
Certain types of ceiling lights, repetitive sounds or driving on curvy roads are guarantees for me.
When I have one, all noise is greatly magnified...all I want is a dark room, with the tv on low on something like Fox news or an old "quiet" type movie. I need a fairly consisitent, level, low decibel noise, that will block out any repetitive-type sound. If I can hear a bird outside the window, it will make screeching chalk on a blackboard seem like nothing.