FIELD: transmission of speech, applicable in portable digital radio telephones for selective modification of a digital signal frame formed by a series of successive frames, when the digital signal represents an audiosignal applied to the transmitter formed by a speech and/or noise components. SUBSTANCE: device for selective modification of a digital signal frame uses a device for estimation of the power level, speech component detector, noise estimate device operating when the speech component detector determines that the speech component does not form parts of the frame, reference table containing a great number of lead-ins; every lead-in is provided with an index indicating the level of noise estimates, and a filter for reception of the digital signal frame, whose characteristics may be selected by the lead-in of the reference table that has been referred tom and the lead-in corresponds to the adapted noise estimate obtained by the noise estimate device. EFFECT: enhanced speech articulation. 9 cl, 16 dwg
