apparatus located aboard a platform situated in an acoustic environment forracking a moving body when the body is proximate to the platform . the apparatus includes a selected number of acoustic sensor elements at selected locations around the platform , each of the elements for detecting acoustic information arriving at its selected location . the apparatus further includes signal conditioners coupled to the sensor elements , a given one of the signal conditioners providing a conditioned signal representing acoustic information which is emitted by the moving body when the body is proximate to the platform , and which arrives at the location of the acoustic sensor element to which the given signal conditioner is coupled . a processor receives conditioned signals from respective signal conditioners and enables comparisons of selected characteristics of the received signals to the made in order to determine a selected parameter which is related to the movement of the body when the moving body is proximate to the platform .