a signal from a submarine an underwater animal or an acoustic tomography experiment a first preferred embodiment according to the present invention will now be described with reference to fig1 which is a flowchart depicting essential as well as non essential steps of the inventive match phase noise mpn filtering method to implement the mpn filtering method an input time series consisting mostly of noise is received during step 1 and a good estimate of the frequency dependence of the noise spectrum in the form of an estimated noise spectrum is input during step 2 for reasons discussed in greater detail below the more accurate the noise estimate the more sensitive the mpn filtering method becomes it should be mentioned that the noise does not have to be u2018 white u2019 corresponding to a constant power spectrum and that absolutely no knowledge of the phases of the noise components is required moreover no knowledge of whatever signal the noise may be obscuring is required it should also be noted at this juncture that the noise spectrum need not be obtained in approximately real time but may be obtained from an appropriate data base of noise spectra such a data base can advantageously be indexed using a variety of parameters and preferably the noise spectra are indexed by wind speed and or sea state during step 3 the mpn filter executes a fast fourier transform fft of the input time series of the signal received during.