At this point of time, your child would learn to get familiar with the voices of the people who are mostly present close to him. Moreover, he would also learn to differentiate the voices of strangers, which is indeed a good recognition trait advancing in your little prince.
What you need to know You as a parent need to polish this skill by testing your baby time to time. The best way is to ask one of your friends who is not known by your toddler hide behind the door. Ask him to call out your baby’s name without being seen. Your toddler would surely grow anxious as soon as he catches an unfamiliar voice. This is a wonderful sign of verbal development.