This paper presents some novel results concerning the problem of enhancing speech degraded by wideband additive noise. The enhancement scheme proposed in this work is based on the utilisation of the Auditory Masking mechanism as a measure for the definition and subsequent suppression of the frequency audible noise components. Accordingly, the enhancement technique minimises only those noise components responsible for audible signal degradations, so that the underlying speech signal quality is only minimally degraded. Extensive subjective and objective tests have shown that, after enhancement, the intelligibility of the processed signal can be improved even at very low S/N ratios.