Change in the amplitude envelope and transition duration were suggested as acoustical cues used in the phonemic distinction between /b/ and /w/. The role of these acoustical cues in phonetically based trading relations was examined by assessing the ability of normal and hearing-impaired listeners to identify stimuli on two synthetic /b/-/w/ continua. These continua differed in their amplitude envelope, but changed in the same way along the dimension of transition duration. Results indicated, that both groups of listeners demonstrated the categorical perception in both amplitude type conditions. Furthermore, it was found that the phonemic boundary was dependent on both the type of continuum used and the listeners hearing status.