signals and phase opposition and hence cancellation of the acoustic ringing phase cycling of the inversion pulse may also be employed in the latter technique to suppress acoustic ringing stimulated by the inversion pulse application_number US 34057682 A description turning now to fig1 the classic spin echo measurement of prior art is implemented by the sequence of fig1 a 90 u00b0 pulse 10 rotates the z component of magnetization into the x y plane in accord with the usual convention the z axis is taken parallel to the polarizing magnetic field the precession frequency of the magnetization vector is distributed over the frequency spectrum in a frequency interval determined by chemical shifts of the sample after a period 12 of length u03c4 during which the precession frequency distribution disperses over a frequency interval determined by the chemical shifts a 180 u00b0 pulse 14 is applied to invert the magnetization in the z axis this is operatively equivalent to inversion of the phase dispersion of all precessing vectors after a re focusing period 16 again of length u03c4 the signal 18 is observed the signal during this process attenuates exponentially with time constant 2 u03c4 t 2 where t 2 is the transverse relaxation time where acoustic ringing decays with a.