$1/f$ noise under conditions of interaction between phase transitions

Vibrational modes of combustion under conditions of combustible liquid boiling before the reaction front are investigated experimentally. Fluctuations are observed with the spectral density inversely proportional to frequency ($1/f$ noise). This phenomenon is associated with the intersection and interaction of nonequilibrium phase transitions. A mathematical model is suggested of the emergence of fluctuations with a $1/f$ spectrum under conditions of interaction between subcritical and supercritical phase transitions in a distributed system.