A plausible explanation for learners having difficulties with the acquisition of L2 phonology is the idea that L2 speech is processed through the L1 and perceived in relation to it.  L2 learners sometimes fail to perceive the differences between L1 and L2 segments; consequently, they are unable to acquire new sounds. In this context, the concept of perceptual salience takes on added importance because learners might be able to establish differences between L1 and L2 sounds if they are perceptually prominent in the L2 input. Some researchers suggest that multimedia environments are beneficial because the language input can be highlighted in many ways and thus render opaque forms more salient to the learner. This study investigates the extent to which pedagogical instruction using text-to-speech (TTS) technology as a means to enhance the aural input assists learners in the acquisition of the English /I/. Three groups of learners of the same L1 (Spanish) and similar English proficiency were pre-tested on their ability to perceive and produce the target vowel by means of different tasks (two for each ability). Each group was subjected to a different instructional condition: TTS-based instruction, non-TTS based instruction and regular classroom instruction. The TTS group performed tasks intended to develop their perception of the target forms via TTS; the non-TTS group performed the same tasks, but receiving input from the researcher; and the third group worked on listening comprehension tasks. It was hypothesized that the TTS group would outperform the other two groups in terms of perception and production. After completing the treatments, the three groups were tested on their productive and perceptual abilities in relation to the target sound. Two weeks later, the participants received the same tests. The results obtained showed that the TTS group significantly outperform the non-TTS group in one of the pronunciation tasks. However, their performance in the other tasks in the post-tests was not significantly different from the other groups. These results are discussed with respect to the hypotheses proposed and in relation to the relevant theory and previous studies. The limitations of the study together with suggestions for future research and its implications for ESL teaching are also addressed.