Method for monitoring the physical state of a longitudinal element , characterized in that it comprises: - a step of detection of the mechanical waves moving along the longitudinal element by means of an array of mechanical wave sensors placed along and in contact with the longitudinal element, said array comprising at least a first pair (A) of sensors each positioned at one end of a first portion of the longitudinal element , and - a processing step comprising • determining a plurality of simplified traces (S corAP1-Pi ), each simplified trace (S corAPi ) resulting from the interferometry of signals (S 1-P1 , S 2-P1 ) delivered by the sensors of the first pair A over a predetermined time period (Pi), the method being characterized in that the processing step comprises: • determining at least a first virtual trace and a second virtual trace (S somA1 , S somA2 ), the first virtual trace (S somA1 ) corresponding to the sum of simplified traces determined during a first monitoring interval and the second virtual trace (S somA2 ) corresponding to the sum of simplified traces determined during a second monitoring interval, the first and the second monitoring intervals being different and each comprising a plurality of predetermined time periods, and • comparing at least the first virtual trace (S somA1 ) with the second virtual trace (S somA2 ) in such a way as to extract at least one piece of information on the physical state of the first portion . - a step of detection of the mechanical waves moving along the longitudinal element by means of an array of mechanical wave sensors placed along and in contact with the longitudinal element, said array comprising at least a first pair (A) of sensors each positioned at one end of a first portion of the longitudinal element , and - a processing step comprising • determining a plurality of simplified traces (S corAP1-Pi ), each simplified trace (S corAPi ) resulting from the interferometry of signals (S 1-P1 , S 2-P1 ) delivered by the sensors of the first pair A over a predetermined time period (Pi), the method being characterized in that the processing step comprises: • determining at least a first virtual trace and a second virtual trace (S somA1 , S somA2 ), the first virtual trace (S somA1 ) corresponding to the sum of simplified traces determined during a first monitoring interval and the second virtual trace (S somA2 ) corresponding to the sum of simplified traces determined during a second monitoring interval, the first and the second monitoring intervals being different and each comprising a plurality of predetermined time periods, and • comparing at least the first virtual trace (S somA1 ) with the second virtual trace (S somA2 ) in such a way as to extract at least one piece of information on the physical state of the first portion . • determining at least a first virtual trace and a second virtual trace (S somA1 , S somA2 ), the first virtual trace (S somA1 ) corresponding to the sum of simplified traces determined during a first monitoring interval and the second virtual trace (S somA2 ) corresponding to the sum of simplified traces determined during a second monitoring interval, the first and the second monitoring intervals being different and each comprising a plurality of predetermined time periods, and • comparing at least the first virtual trace (S somA1 ) with the second virtual trace (S somA2 ) in such a way as to extract at least one piece of information on the physical state of the first portion . <EOS>