Abstract: A system includes a controlled acoustic source. The system also includes distributed acoustic sensors along a conduit. The distributed acoustic sensors obtain acoustic signal measurements as a function of position along the conduit in response to at least one acoustic signal provided by the controlled acoustic source. The system also includes a processing unit that generates an acoustic activity plot or report based on the acoustic signal measurements. The acoustic activity plot or report is used to identify at least one acoustic impedance boundary anomaly as a function of position along the conduit.