Two experiments were carried out to evaluate the perceptual effect of various enhancements made to information-rich regions of intervocalic consonants. The first tested the benefits of altering the relative amplitude of such regions, whilst the second additionally employed filtering to produce stylised cues to phonetic contrasts. After such manipulations stimuli were combined with speech-shaped noise at 0 and -5dB SNR, and presented to normally-hearing listeners. All enhanced conditions led to statistically significant increases in intelligibility relative to the unenhanced condition. These results demonstrate the benefits of knowledge-based enhancement techniques which target acoustic cues to phonetic contrasts.