  We use a mobile impurity or depleton model to study elementary excitations in
one-dimensional integrable systems. For Lieb-Liniger and bosonic Yang-Gaudin
models we express two phenomenological parameters characterising renormalised
inter- actions of mobile impurities with superfluid background: the number of
depleted particles, $N$ and the superfluid phase drop $\pi J$ in terms of the
corresponding Bethe Ansatz solution and demonstrate, in the leading order, the
absence of two-phonon scattering resulting in vanishing rates of inelastic
processes such as viscosity experienced by the mobile impurities
