Traditionally, auditory spectral resolution is studied psychophysically by masking experiments (i.e., the effect of a masking stimulus on the detection threshold of a test tone with variable frequency). During the last decade there has been increasing experimental evidence of an essential qualitative difference between the results of two classes of such experiments: (a) masking stimulus and test tone being presented simultaneously (direct masking) or (b)nonsimultaneously (forward masking, pulsation threshold). This difference can be interpreted as an effect of lateral suppression (spectral sharpening) which manifests itself only in case of nonsimultaneous presentation of masking stimulus and test tone. An overview of the relevant data is presented (e.g., auditory Mach bands, two‐tone suppression, increased ripple resolution, etc.), with occasional references to related electrophysiological data. The experimental data lead to the notion of a peripheral stage of spectral sharpening of such a nature that it does not affect the detection threshold of a test tone in direct masking.