1. A method for discriminating and attenuating the echoes of a digital audio signal generated from a transform encoding stage, which generates echoes, wherein the encoding also comprises, in parallel with the transform encoding stage, which generates echoes, a time encoding stage, which does not generate echoes, the method including at least in the decoding, for each current frame of this digital audio signal, the following steps: discriminating a low-energy zone of the current frame preceding a transition to a high-energy zone of the current frame; defining a false-alarm zone corresponding to the non-discriminated zones of the current frame; determining an initial processing of the echoes with attenuation gain values of the current frame; attenuating the echoes according to the initial processing of the echoes in said low-energy discriminated zones of the current frame; inhibiting the attenuation of the echoes in the initial processing in the false-alarm zone; wherein said determination of the initial processing of the echoes comprises, in the decoding, for each current frame of this digital audio signal: comparing, in real time, in at least one frequency band, a value representative of a variable obtained from a characteristic of the time envelope of the signal obtained from an echo-generating decoding and of a variable obtained from the corresponding characteristic of the signal obtained from a non-echo-generating decoding to a threshold value; and according to the result of this comparison, concluding on the existence or the non-existence of an echo obtained from the transform encoding in the current frame; and, if an echo exists, determining the initial attenuation gain values of the echoes according to said variables obtained from said echo-generating decoding and from said non-echo- generating decoding.