▁as ▁ ▁and ▁ ▁and ▁the ▁latter ▁as ▁ ▁and ▁), ▁keeping ▁their ▁ph on em ic ▁distinction , ▁while ▁in ▁the ▁south ▁they ▁were ▁hom organ ic . ▁ ▁The ▁first ▁step ▁away ▁from ▁that ▁system ▁was ▁the ▁de aff ric ation ▁of ▁ ▁in ▁the ▁first ▁quarter ▁of ▁the ▁ 1 6 th ▁century . ▁Because ▁of ▁a ▁differ ing ▁place ▁of ▁art ic ulation , ▁this ▁still ▁contrast ed ▁with ▁ ▁in ▁the ▁prest ige ▁dialect ▁of ▁north ▁central ▁Spain , ▁though ▁it ▁was ▁a ▁complete ▁mer ger ▁for ▁southern ▁dialect s . ▁ ▁The ▁second ▁step ▁was ▁the ▁de vo icing ▁of ▁vo iced ▁s ibil ants . ▁ ▁In ▁the ▁north , ▁ ▁and ▁ ▁were ▁lost , ▁though ▁ ▁remained ▁contrast ive ▁as ▁there ▁had ▁been ▁no ▁vo ic eless ▁. ▁ ▁This ▁sound ▁ ▁contrast ed ▁with ▁two ▁ac oust ically ▁similar ▁sounds : ▁d ento al ve olar ▁ ▁and ▁ap ico al ve olar ▁. ▁ ▁By ▁ 1 6 0 0 , ▁ ▁had ▁de aff ric ated ▁and ▁merged ▁with ▁. ▁ ▁Sub sequ ent ▁changes ▁to ▁the ▁sound ▁system ▁of ▁Spanish ▁retained ▁the ▁contrast s ▁while ▁en han cing ▁the ▁segments ▁by ▁increasing ▁art icul atory ▁distance ▁amongst ▁their ▁rather ▁subt le ▁ac oust ic ▁contrast s , ▁an ▁appropriate ▁step ▁due ▁to ▁the ▁high ▁product ivity ▁of ▁these ▁ph on emes ▁in ▁differenti ating ▁frequently ▁used ▁minimal ▁pairs . ▁The ▁d ento al ve olar ▁one ▁was ▁moved ▁" forward