  Inspired by medical applications of high-intensity ultrasound, we study a
coupled elasto-acoustic problem with general acoustic nonlinearities of
quadratic type as they arise, for example, in the Westervelt and Kuznetsov
equations of nonlinear acoustics. We derive convergence rates in the energy
norm of a finite element approximation to the coupled problem in a setting that
involves different acoustic materials and hence jumps within material
parameters. A subdomain-based discontinuous Galerkin approach realizes the
acoustic-acoustic coupling of different materials. At the same time,
elasto-acoustic interface conditions are used for a mutual exchange of forces
between the different models. Numerical simulations back up the theoretical
findings in a three-dimensional setting with academic test cases as well as in
an application-oriented simulation, where the modeling of human tissue as an
elastic versus an acoustic medium is compared.
