The normalized amplitude of shear waves versus distance between the magnet and the PVA sample is illustrated in Figure \ref{Figure5}-(A); versus distance between the coil and the PVA sample along the Z axis in Figure \ref{Figure5}-(B); and versus distance between the center of the coil and the center of the ultrasound probe along X axis (0 being defined as the coil center aligned with the probe center) in Figure \ref{Figure5}-(C). Amplitude of shear waves was measured as the mean squared displacement between 15 and 25 mm of the coil inside the medium, an arbitrary location where shear waves had high amplitudes. Amplitudes were normalized by the maximum measured, respectively at a distance of 4 mm between the magnet and the sample, 10 mm between the coil and the medium and 0 mm between the center of coil and the center of probe.

We observed a decrease of the shear wave amplitude when the distance between the medium and the magnet increased, with an excellent agreement between experimental and numerical results. This was expected as the magnetic field decreased with distance. Similar observations can be made when the coil is drawn further from the sample. When we moved the coil along the X direction, we observed a strong maximum between two minima separated by 75 mm, corresponding to the length between the two centers of the TMS coil, which is also in agreement with the current density profile along this direction.