Method of monitoring a reservoir, in particular a reservoir made of composite material, preferably intended for storing gas at high pressure, the reservoir being provided with at least one acoustic sensor during the monitoring, the method being characterised in that it comprises the following steps: - filling the reservoir with a fluid, - acquiring data relating to the amplitude and the energy of acoustic emissions resulting from the filling, with the aid of the one or more sensors (51, 52), - determining at least one critical threshold value (S c) on the basis of a linear combination between data relating to the amplitude and the energy, obtained for a cluster of zonally-localised signals in the listening radius of the one or more sensors, determined according to the following formula: ∑ i = 1 N A i A i max + E i E i max where N: number of acoustic emissions, more precisely the number of bursts in the localised cluster; A i: amplitude cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, A i max: maximum amplitude over at least one sensor placed on the shell of the reservoir during the acoustic emission i, E: energy cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, the energy being the integral of the amplitude squared, E i max: maximum energy over at least one sensor placed on the shell of the reservoir during the acoustic emission i, - as a function of this critical threshold value (S c), deducing therefrom a state of the reservoir. - filling the reservoir with a fluid, - acquiring data relating to the amplitude and the energy of acoustic emissions resulting from the filling, with the aid of the one or more sensors (51, 52), - determining at least one critical threshold value (S c) on the basis of a linear combination between data relating to the amplitude and the energy, obtained for a cluster of zonally-localised signals in the listening radius of the one or more sensors, determined according to the following formula: ∑ i = 1 N A i A i max + E i E i max where N: number of acoustic emissions, more precisely the number of bursts in the localised cluster; A i: amplitude cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, A i max: maximum amplitude over at least one sensor placed on the shell of the reservoir during the acoustic emission i, E: energy cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, the energy being the integral of the amplitude squared, E i max: maximum energy over at least one sensor placed on the shell of the reservoir during the acoustic emission i, N: number of acoustic emissions, more precisely the number of bursts in the localised cluster; A i: amplitude cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, A i max: maximum amplitude over at least one sensor placed on the shell of the reservoir during the acoustic emission i, E: energy cumulated over at least one sensor placed on the shell of the reservoir during the acoustic emission i, the energy being the integral of the amplitude squared, E i max: maximum energy over at least one sensor placed on the shell of the reservoir during the acoustic emission i, - as a function of this critical threshold value (S c), deducing therefrom a state of the reservoir.