the second step was the devoicing of voiced sibilants. in the north, and were lost, though remained contrastive as there had been no voiceless . this sound contrasted with two acoustically similar sounds: dentoalveolar and apicoalveolar . by 1600, had deaffricated and merged with . subsequent changes to the sound system of spanish retained the contrasts while enhancing the segments by increasing articulatory distance amongst their rather subtle acoustic contrasts, an appropriate step due to the high productivity of these phonemes in differentiating frequently used minimal pairs. the dentoalveolar one was moved "forward" to interdental , losing its former sibilance in the process (which increased its acoustic distance to the remaining sibilant ), and the prepalatal one was moved "backward" to velar also losing its former sibilance. all in all resulting in the three-way distinction found in modern standard peninsular pronunciation: