  The attenuation of low-intensity acoustic waves in the suspension of
ultrasound contrast agents (UCAs, microbubbles) is determined by the
oscillation of the microbubbles in the medium. This bubble-induced attenuation
is a linear phenomenon and can be estimated via a linearized Rayleigh-Plesset
equation (RPE). In the material characterization, theoretical attenuation is
estimated from steady state oscillation of an UCA and immediately compared with
experimental attenuation data that are usually measured by shot-pulse
ultrasound. However, discrepancy could exist in the characterization if the UCA
does not ring up to steady state oscillation. In this article, we investigate
the situation where the transient solution of the RPE is not negligible and
discuss its impact on the modeling of the shell parameters of an UCA. We
provide a formula for attenuation estimation considering the contribution due
to transient oscillation.
