2 Months!

Coos are your baby's way of expressing delight, as well as exercising his vocal cords. You can carry on a "conversation" with your baby now. When he gurgles or coos, say something brief or coo back at him. Then wait for him to "say" something back to you. This kind of conversational turn-taking may not sound like much to you now, but it's actually the beginning of learning how to talk.
Your baby can tell the difference between familiar voices and other sounds, and he's becoming a better listener. He can also show you that he's in tune with his environment. Notice how he looks to see where certain noises are coming from.

An ongoing conversation (although seemingly one-sided) can help your baby develop his sense of place. He may even watch your mouth as you talk, fascinated by how it all works. You'll be amazed by his ability to communicate with a growing repertory of coos (musical, vowel-like sounds), smiles, and unique cries to express his different needs.