The invention addresses the problem of recovering an unknown signal from multiple records of brief duration which are presumed to contain the signal at mutually random delays in a background of independent noise. The scenario is relevant to many applications, among which are the recovery of weak transients from large arrays of sensors and the identification of recurring patterns through a comparison of sequential intervals within a single record of longer duration. A simple and practical approach is provided by solving this problem through higher-order spectra. Applying the method to the third-order spectrum, the bispectrum, leads to filters derived from cross bicoherence.