The distribution of time intervals between incipient bubbles was measured in a venturi, which simulates conditions in hydraulic machinery and highspeed flow channels. The statistics of bubble inception were analyzed and indicated that two-phase inception due to a pressure reduction in high-speed flow may be modeled as random inception of bubble trains with bubble clusters forming periodically within a train. These fundamental experimental observations may be useful for the development of a monitoring system for two-phase (cavitation and/or boiling) detection in sodium-cooled fast reactors or pressurized water reactors