Fig. 2.

Fourier spectrum of the scattered pressure from a monodisperse population of 100 bubbles with a radius of 1.1 μm (left column), and the fundamental spectral component as a function of the resting bubble radius under the same conditions as in the corresponding left plot (right column). Bubbles are insonified with a 10-cycle, 4 MHz, 210 kPa Blackman-windowed pulse. The shell parameters are (a) κ_S=0.5·10⁻⁸ kg/s, χ=0.25 N/m; (b) κ_S=1.0·10⁻⁸ kg/s, χ = 0.54 N/m; (c) κ_S=1.5·10⁻⁸ kg/s, χ = 0.8 N/m. The dashed line corresponds to free bubbles. The solid lines correspond to bound bubbles and show the effect of (1) coherent echo summation and (2) coherent echo summation + wall. The dotted line shows the effect of coherent echo summation + wall + bubble aggregates.