An optimization approach to a three‐dimensional acoustic inverse problem in the time domain

An optimization approach to a three‐dimensional acoustic inverse problem is considered in the time‐domain. The velocity and the density are reconstructed by minimizing an objective functional. By introducing a dual function, the gradient of the objective functional is found with an explicit expression. The parameters are then reconstructed by an iterative algorithm (the conjugate gradient method). The uniqueness of the solution is also proved.