Method and system for characterising a medium using ultrasound

An ultrasound characterisation method of a medium, comprising:

• generating a series of incident ultrasound waves in a zone of interest of said medium, by means of an array of transducers, said series of incident ultrasound waves being an emission base;
• and
• measuring a canonical reflection matrix Rui(t) defined between the input emission base (i) and an output reception base (u), the coefficients of this canonical reflection matrix corresponding to the signals received by the transducers and induced by the ultrasound waves reflected in the medium;
• said method further comprising a correction process comprising:
• determining a set of responses R of the medium which are obtained by a focusing process for several frequencies f of the signals received from the reflected ultrasound waves and for several points of spatial position r=(x,z) of a region around a reference point of spatial position rp=(xp, zp) from the canonical reflection matrix Rui(t) for a sound speed model c0,
• determining a frequency correction law Φ by averaging or correlating the responses of the medium at different spatial position points (x,z) around the reference point, the frequency correction law being adapted to the reference point and being determined at frequencies f, and
• determining the corrected responses R′ of the medium by applying the frequency correction law Φ to the responses R of the medium around the reference point and for the plurality of frequencies f.