A method for activating multiple sources (S1-S7) towed by one or more survey vessels, the method comprising: generating a set of random seed time delays within the duration of shot intervals; and assigning each random seed time delay to one of the multiple sources; the method characterized by: dividing the duration of the shot intervals of a marine-survey-time line into a set of duration groups; pseudo-randomly arranging the duration groups into a schedule of duration groups; and for each shot interval of a marine-survey-time line, randomly selecting (1303, 1304) a time delay from the source with the shortest random seed time delay from the duration that is next in the schedule; and pseudo-randomly shifting the random seed time delays of the multiple sources to generate the shifted time delays of the multiple sources by assigning the time delay to the source of the multiple sources with a shortest random seed time delay, calculating a difference between the time delay and the shortest random seed time delay, and adding the difference to the random seed time delays of remaining sources to generate shifted time delays of the remaining sources; and firing the multiple sources within the shot interval based on the shifted time delays. generating a set of random seed time delays within the duration of shot intervals; and assigning each random seed time delay to one of the multiple sources; the method characterized by: dividing the duration of the shot intervals of a marine-survey-time line into a set of duration groups; pseudo-randomly arranging the duration groups into a schedule of duration groups; and for each shot interval of a marine-survey-time line, randomly selecting (1303, 1304) a time delay from the source with the shortest random seed time delay from the duration that is next in the schedule; and pseudo-randomly shifting the random seed time delays of the multiple sources to generate the shifted time delays of the multiple sources by assigning the time delay to the source of the multiple sources with a shortest random seed time delay, calculating a difference between the time delay and the shortest random seed time delay, and adding the difference to the random seed time delays of remaining sources to generate shifted time delays of the remaining sources; and firing the multiple sources within the shot interval based on the shifted time delays. dividing the duration of the shot intervals of a marine-survey-time line into a set of duration groups; pseudo-randomly arranging the duration groups into a schedule of duration groups; and for each shot interval of a marine-survey-time line, randomly selecting (1303, 1304) a time delay from the source with the shortest random seed time delay from the duration that is next in the schedule; and pseudo-randomly shifting the random seed time delays of the multiple sources to generate the shifted time delays of the multiple sources by assigning the time delay to the source of the multiple sources with a shortest random seed time delay, calculating a difference between the time delay and the shortest random seed time delay, and adding the difference to the random seed time delays of remaining sources to generate shifted time delays of the remaining sources; and randomly selecting (1303, 1304) a time delay from the source with the shortest random seed time delay from the duration that is next in the schedule; and pseudo-randomly shifting the random seed time delays of the multiple sources to generate the shifted time delays of the multiple sources by assigning the time delay to the source of the multiple sources with a shortest random seed time delay, calculating a difference between the time delay and the shortest random seed time delay, and adding the difference to the random seed time delays of remaining sources to generate shifted time delays of the remaining sources; and assigning the time delay to the source of the multiple sources with a shortest random seed time delay, calculating a difference between the time delay and the shortest random seed time delay, and adding the difference to the random seed time delays of remaining sources to generate shifted time delays of the remaining sources; and firing the multiple sources within the shot interval based on the shifted time delays.