Abstract: A method and device for attenuating wideband spurious noises to improve the signal-to-noise ratio of a tracked acoustic signal. Two sensors (1 and 2) are provided, one of which receives the disturbed tracked signal and the other the spurious noises, to feed a plurality of correlation modules (4) via as many spectrum-line filters (3) distributed throughout the useful bandwidth of sensor (1), each of said correlation modules (4) supplying a correction signal and the sum of said correction signals being subtracted from the signal given by sensor (1) to yield a noise-free tracked signal. The invention is applicable to acoustic reception systems used in noisy environments.

Abstract: Frequency summing device comprising a summing element effecting the summing of the output signals of a first multiplier receiving a signal whose frequency is f and a signal whose frequency is F and of a second multiplier receiving the signal whose frequency is f and the signal whose frequency is F after dephasing by 90.degree.. The dephasing by 90.degree. is obtained by a complex circuit comprising three elementary dephasers in series provided with an attenuator and an adder effecting the sum of the output signals of the attenuator and of the first dephaser.