In order to characterize the lift-off acoustic environment of launch vehicles, EADS has developed an inverse method via a time domain boundary integral equation approach using an optimal control method. An industrial application of the method is presented via the identification of acoustic sources of ARIANE 5 from lift-off in-flight measurements. As the lift-off acoustic field is random in nature, the optimization process is performed using the cross-correlation functions matrix measurement. After having characterized the sources from pressure measurements, the complete environment is rebuilt by an acoustic direct computation from the obtained acoustic sources. We finally estimate the loads created by the acoustic field by integrating the resulting pressures over all surfaces of the launchers.